**Selective Reduction of Cr(VI) in Chromium, Copper and Arsenic (CCA) Mixed Waste Streams Using UV/TiO2 Photocatalysis**

### **Shan Zheng, Wenjun Jiang, Mamun Rashid, Yong Cai, Dionysios D. Dionysiou and Kevin E. O'Shea**

**Abstract:** The highly toxic Cr(VI) is a critical component in the Chromated Copper Arsenate (CCA) formulations extensively employed as wood preservatives. Remediation of CCA mixed waste and discarded treated wood products is a significant challenge. We demonstrate that UV/TiO2 photocatalysis effectively reduces Cr(VI) to less toxic Cr(III) in the presence of arsenate, As(V), and copper, Cu(II). The rapid conversion of Cr(VI) to Cr(III) during UV/TiO2 photocatalysis occurs over a range of concentrations, solution pH and at different Cr:As:Cu ratios. The reduction follows pseudo-first order kinetics and increases with decreasing solution pH. Saturation of the reaction solution with argon during UV/TiO2 photocatalysis had no significant effect on the Cr(VI) reduction demonstrating the reduction of Cr(VI) is independent of dissolved oxygen. Reduction of Cu(II) and As(V) does not occur under the photocatalytic conditions employed herein and the presence of these two in the tertiary mixtures had a minimal effect on Cr(VI) reduction. The Cr(VI) reduction was however, significantly enhanced by the addition of formic acid, which can act as a hole scavenger and enhance the reduction processes initiated by the conduction band electron. Our results demonstrate UV/TiO2 photocatalysis effectively reduces Cr(VI) in mixed waste streams under a variety of conditions.

Reprinted from *Molecules.* Cite as: Zheng, S.; Jiang, W.; Rashid, M.; Cai, Y.; Dionysiou, D.D.; O'Shea, K.E. Selective Reduction of Cr(VI) in Chromium, Copper and Arsenic (CCA) Mixed Waste Streams Using UV/TiO2 Photocatalysis. *Molecules* **2015**, *20*, 2622-2635.

#### **1. Introduction**

The practice of using chemicals to protect wood products from biological degradation and deterioration has been effectively used for nearly a century. One of the most widely used wood preservatives is Chromated Copper Arsenate (CCA), a mixture of oxyanions of chromium, copper and arsenic [1]. A number of different proportions of Cr:As:Cu have been employed as wood preservatives. The role of copper in CCA treated wood is to protect the wood from the attack of bacteria and fungi; arsenic plays the role of insecticide while chromium acts as a binder of arsenic and copper to the wood surface [2]. Human exposure to these toxic metals can occur from direct contact with the wood (dermal sorption), inhalation of wood dust [3] or from CCA leachate or waste streams leading to contaminated water and soil [4]. These metals/metalloids pose significant threats to human health and the environment. The highly toxic and carcinogenic nature of arsenic is well documented [5]. An estimated 50 to 100 million people suffer or are threatened from the negative health effects caused by the ingestion of arsenic contaminated water. In aqueous media, arsenic typically exists as arsenate, As(V) and arsenite, As(III).While both As(III) and As(V) are stable and toxic, As(III) is more poisonous and more mobile than As(V).Chromium, in the third oxidation state, Cr(III), is an essential micronutrient for human health however, it is highly toxic and carcinogen in the Cr(VI) state [6]. Although less pronounced, copper can also exert adverse effects on human health at high levels of exposure despite its important function as a nutrient at trace level concentrations [7]. The co-existence of these metals can be more toxic compared to the toxicity associated with each metal individually [8].

In response to the concern over the leaching of CCA from the treated wood products, such as playground equipment, patios, picnic tables, residential uses of CCA woods were banned in USA and Canada in 2004. However, the use of CCA treated wood is still allowed for a variety of commercial, industrial and agricultural purposes. Approximately, 300 million cubic meters of wood are treated with CCA, annually, consuming nearly 500,000 tons of CCA preservative formulations [9]. The extensive and sustained use of CCA preserved wood has led to the generation of significant quantities of CCA treated woodwaste which is predicted to reach approximately 9 million m3 /year by 2015 in USA and 2.5 million m3 /year by 2025 in Canada [10]. Various extraction methods including supercritical fluid extraction [11], hydrogen peroxide extraction [12], EDTA extraction [13], oxalic acid extraction [14], have been reported in the literature for the separation of Cr, Cu and As from CCA treated woodwaste. Unfortunately, these methods can suffer from limitations of low extraction efficiencies, long treatment times, interference from other metals, and high cost [11–15]. Proper handling and disposal of CCA woodwaste is a serious challenge as ultimately these toxic metals can leach from wood through aging and weathering processes leading to discharge of the toxic metals into the environment. Landfill is still the most common fate of CCA treated woodwaste in many countries including USA and Canada as CCA wood products are not currently categorized as hazardous waste [16].Once deposited into the landfills, CCA treated products leach toxic arsenic and chromium species into the environment through aqueous runoffs and pose a serious threat to human life and to the surrounding environment [17]. Thus there is an urgent need to identify an environmentally sound and cost effective method to treat CCA contaminated leachates and explore possible strategies to recover the metals for future use.

The toxicity of these metals can be dramatically influenced by their oxidation state. In CCA, Cu and As exist as oxides of Cu(II) and As(V) [18]. Cr is present as Cr(VI) in CCA before fixation, which involves a reductive process leading to partial conversion to Cr(III) during binding with wood lignin [19]. Cr(VI) is toxic and mobile in the environment while Cr(III) is less toxic and a number of reductive processes including photocatalysis can effectively transform Cr(VI) to Cr(III) [20]. Chromium species can be removed and recovered from aqueous media employing adsorption or precipitation processes [21,22]. While semiconductor mediated photocatalysis can be used to oxidize an extensive number of pollutant and toxins, a relatively limited number of examples have appeared on effective applications for reductive transformations of pollutants and toxins [23]. Among semiconductor photocatalysts, TiO2 is most extensively studied for water purification. Upon photo-excitation of TiO2 with wavelengths 385 nm, an electron/hole pair is produced, Equation (1), the hole can initiate oxidation through electron transfer with water, Equation (2) or a metal at the surface Equation (3), while the electron can act as a reducing agent to molecular oxygen, Equation (4) or metal ions, Equation (5):

$$TiO\_2 \xleftarrow{hv} h^+ + e^- \tag{l}$$

$$h^{+} + H\_{2}O \rightarrow HO^{\*} \tag{2}$$

$$HO^{\bullet} + m^{n+} \to m^{n+2} \tag{3}$$

$$e^- + \mathcal{O}\_2 \to \mathcal{O}\_2^{\star-} \tag{4}$$

$$e^{-} + m^{n+} \to m^{n-1} \tag{5}$$

A number of reports have appeared in the literature on the TiO2 adsorption and photocatalytic reduction of Cr(VI) [24–32]. TiO2 materials can have strong metal ion adsorption properties and are thus attractive for adsorption and photo-initiated treatment as simultaneous processes for the removal of heavy metals from the contaminated waste streams and leachates. Since adsorption of Cr(VI) at the surface of the semiconductor is critical for effective reduction during photocatalysis, it is important to examine the effects of As and Cu in the treatment strategies for CCA waste streams. In this study, we have demonstrated the effective reduction of Cr(VI) to Cr(III) using TiO2 photocatalyst in presence of As(V) and Cu(II). We have also investigated the influence of solution pH and CCA formulations on the reduction of Cr (VI) to Cr (III).

#### **2. Results and Discussion**

#### *2.1. The Reduction of Cr(VI)*

In a typical experiment, a suspension of TiO2 was prepared with a CCA stock solution and transferred to a Pyrex reaction vessel. The reaction solution was purged with oxygen, air, or argon, and irradiated with UV light. Analyses were performed at specific time intervals. In the presence of TiO2, oxygen and UV irradiation, Cr(VI) is readily converted to Cr(III) which is measured from the difference of initial and final concentration of Cr(VI). Control experiments established the negligible reduction (<3%) of Cr(VI) in the absence of TiO2 and very little adsorption (<1%) of Cr(VI) on TiO2 in the dark. The purging of the CCA reaction solution with different gases (Ar, air, O2) prior and during irradiation had minimal effect on the photocatalytic reduction of Cr(VI) shown in Figure 1. These results are consistent with previous reports on the adsorption and reduction of Cr(VI) during TiO2 photocatalysis [33]. The pKa and speciation of arsenic and chromium metals are shown in Table 1. Copper exists as non-protonated copper oxide form.

The solution pH has a pronounced effect on the Cr(VI) species and surface charge of TiO2. The pKa1 and pKa2 of chromic acid (shown in Table 1) are 0.7 and 6.5, respectively. The zero point of charge (ZPC) of P25 TiO2 is 6.8 [34]. Hence, the reduction of Cr(VI) was investigated as a function of solution pH. When the solution pH is less than 6.8, the TiO2 is positively charged and the predominant Cr(VI) species HCrO4 í and CrO4 2í are negatively charged. The photocatalytically initiated reactions mainly occur at or near the surface of TiO2 and thus electrostatic attraction between charged substrate and oppositely changed surface can lead to strong adsorption and enhance the reactivity or reduction of Cr(VI) at solution pH below 6.8. As the solution pH increases above 6.8, the TiO2 surface becomes progressively more negatively charged while the predominant Cr(VI) species is CrO4 2í. The electrostatic repulsion between the negatively charged TiO2 surface and CrO4 2íinhibits Cr(VI) adsorption and retards reduction.

**Figure 1.** The effect of dissolved argon, oxygen and air on the reduction of Cr(VI). [Cr(VI)] = 40 μM, [TiO2] = 0.10 g/L, pH = 3, 350 nm.

**Table 1.** pKa and speciation of chromium and arsenic.

UV/TiO2 processes often following pseudo-first order kinetics according to Equation (6), below.

$$\ln(\text{Ca/C}) = \text{kt} \tag{6}$$

where k is the rate constant of pseudo-first order model (miní1 ), t is time (min), C0 is the initial concentration of Cr(VI) and C is the concentration of Cr(VI) at the specific time.

The reduction of Cr(VI) was monitored as a function of irradiation time at several different initial Cr(VI) concentrations. The UV/TiO2 photocatalytic reduction of Cr(VI) was measured over a range of solution pH from ~3.0 to 10.0 with the fastest occurring under acidic conditions (Figure 2). The pH effect has been rationalized based on adsorption and the role of electrostatic interactions between TiO2 surface and chromate species which are attractive at low pH and repulsive at high pH [33].

**Figure 2.** Investigation of reaction kinetics of Cr(VI) reduction as a function of solution pH. [Cr(VI)] = 40 μM; [TiO2] = 0.10 g/L, 350 nm.

#### *2.2. The Reduction of Cr(VI) in Presence of As(V) at pH 3.0*

While transformation of Cr(VI) to Cr(III) can be achieved by employing UV and visible lightactivated TiO2 materials, the effects of As and Cu on the reduction process have not been reported which is especially important for the treatment of CCA waste streams. The effect of As(V) presence on the reduction rate of Cr(VI) at pH 3.0 is illustrated in Figure 3. While significant reduction of Cr(VI) is observed, the rate of reduction decreased with increasing As(V) concentration. A number of literature reports describe the oxidation of As(III) to less toxic As(V) under TiO2 photocatalysis [34–36]. These reports also established TiO2 photocatalysis does not lead to the reduction of As(V) and thus under our experimental conditions As(V) did not compete with Cr(VI) for the conduction band electrons. We did not detect the presence of As(III) in the reaction solution following the TiO2 photocatalysis treatment. A modest inhibition of Cr(VI) reduction observed upon addition of As(V) and slight decrease of As(V) detected in solution relative to the initial concentration (Figure 4). These results are attributed to the competition between As(V) and Cr(VI) for adsorption at surface active sites where the conduction band electrons are available for reduction of the adsorbate.

**Figure 3.** The reduction of Cr(VI) in the presence of As(V) at pH 3.0. [Cr(VI)] = 40 μM, [As(V)] = 0–80 μM, [TiO2] = 0.10 g/L, 350 nm.

**Figure 4.** The reduction of As(V) in presence of Cr(VI). [Cr(VI**)**]0 = 40 μM, [As(V)]0 = 80 μM, pH = 3, [TiO2] = 0.10 g/L, 350 nm.

#### *2.3. The Reduction of Cr(VI) in Presence of Cu(II)*

The effect of Cu(II), the third component in CCA on the reduction of Cr(VI) is shown in Figure 5. The addition of copper had no significant effect on the UV/TiO2 photocatalytic reduction of Cr(VI) over a range of Cu(II) concentrations. While Cu(II) ions have been used as conduction band electron scavengers during TiO2 photocatalysis, the presence of Cu(II) ions had no effect on the rate of reduction of Cr(VI) under our experimental conditions as illustrated in Figure 6. The concentration of Cu(II) was monitored using atomic absorption throughout the TiO2 photocatalytic reduction of Cr(VI). The changes in the concentration of Cu(II) as a function of irradiation time were insignificant, as shown in Figure 6, indicating no Cu(II) reduction occurred during our UV/TiO2 photocatalysis experiments [32]. These results demonstrate that Cu(II) as included in the CCA formulation does not compete with Cr(VI) for conduction band electrons or critical surface adsorption sites during TiO2 photocatalytic reduction of Cr(VI).

**Figure 5.** The reduction of Cr(VI) in the presence of Cu(II). [Cr(VI)] = 40 μM, [Cu (II)] = 0 μM–80 μM, pH = 3, [TiO2] = 0.10 g/L, 350 nm.

**Figure 6.** The reduction of Cu (II) in presence of Cr(VI). [Cr(VI)]0 = 40 μM, [Cu(II)]0 = 80 μM, pH = 3, [TiO2] = 0.10 g/L, 350 nm.

#### *2.4. Cr(VI) Reduction in Presence of As(V) and Cu(II)*

Treatment of CCA as a mixture is much more practical compared to the processes requiring separation of the metal ions and multiple treatment trains. With this in mind the cooperative effect of Cu(II) and As(V) on the TiO2 photocatalysis reduction of Cr(VI) to Cr(III) was investigated mimicking typical CCA formulations. TiO2 photocatalysis experiments were conducted in presence of 25 ȝM As(V), 25 ȝM Cu(II) and 40 ȝM Cr(VI) under 350 nm irradiation. The reaction suspension was collected and filtered at specific time intervals. Analysis of the solution as a function of treatment time showed that Cr(VI) is reduced to Cr(III) at only a slightly slower rate than the reduction of Cr(VI) alone, in the absence of As and Cu (Figure 7). While the initial concentration of Cu(II) remained unchanged throughout the photocatalytic treatment, the small decrease in the initial As(V) concentration relative to the starting concentration is assigned to strong adsorption on TiO2 surface. Although the addition of Cu(II) alone showed no effect on the rate of Cr(VI) reduction, in presence of 40 ȝm of Cr(VI) and 25 ȝm of As(V), addition of Cu(II) (25 ȝm) lead to a modest increase in the Cr(VI) reduction rate (Figure 8). The small enhancement may be due to interactions between As(V) and Cu(II) and/or competitive adsorption processes which reduces the adsorption of As for active sites on the surface of the TiO2 thus effectively improving the adsorption and subsequent reduction of Cr(VI).

**Figure 7.** TiO2 photocatalysis of Cr(VI) in presence of As(V) and Cu(II). [Cr(VI)] = 40 μM, [As(V)] = 25 μM, [Cu(II)] = 25 μM, pH = 2, [TiO2] = 0.10 g/L, 350 nm.

**Figure 8.** The effect of different Cu(II) concentration on Cr(VI) reduction in presence of As(V). [Cr(VI)] = 40 μM, [As(V)] = 25 μM, [Cu(II)] = 0–40 μM, pH = 3, [TiO2] = 0.10 g/L, 350 nm.

The ratio of the initial concentrations of Cr(VI), As(V) and Cu(II) was varied during TiO2 photocatalysis to model common CCA formulations. At a 0.5:1:1 ratio of Cr(VI):As(V):Cu(II) the fastest and most extensive reduction of Cr(VI) was observed (Figure 9).These changes as a function of CCA formulation are attributed to competitive adsorption among the metals and not for the reactions with the conduction band electrons. The effect of pH on the reduction of 40 ȝm of Cr(VI) in presence of 25 ȝm of As(V) and 25 ȝm of Cu(II) is illustrated in Figure 10. This result suggests that the UV/TiO2 photocatalytic reduction of Cr(VI) is faster underacidic pH conditions both in the presence and absence of As(V) and Cu(II).

**Figure 9.** Cr(VI) reduction at different Cr(VI):As(V):Cu(II) ratios. pH = 3, [TiO2] = 0.10 g/L, 350 nm.

**Figure 10.** The pH effect on Cr(VI) reduction in presence of As (V) and Cu (II). Cr(VI):As(V):Cu(II) = 1.6:1:1. [TiO2] = 0.10 g/L, 350 nm.

#### *2.5. Effect of Hole Scavenger on Cr(VI) Reduction*

Upon irradiation, TiO2 can absorb photons of 385 nm promoting an electron from the valence band to the conduction band forming an electron-hole pair. Rapid recombination of the electron and hole pair prevents redox transformation of adsorbates, and typically an electron scavenger is required to trap the electron and inhibit recombination. UV/TiO2 photocatalysis has been extensively used for oxidative transformation of pollutants and toxins with molecular oxygen purged through the system as an electron scavenger. Molecular oxygen acts as trap for the conduction band electron prolonging the lifetime of the hole and dramatically improving the probability to achieve oxidation of a surface adsorbed species. In the absence of a suitable electron trap little or no oxidative transformation is observed as photo-excitation energy is converted to thermal energy upon recombination.

For the case of Cr(VI), we chose to investigate the influence of adding an electron donor in an attempt to trap the hole, to inhibit recombination and extend the lifetime of the conduction band electron as the desired species to facilitate the reduction of Cr(VI). Formic acid can scavenge the valence band hole and is readily adsorbed onto the surface under neutral and acidic solution pH leading to an inhibition of recombination of electron and hole pairs on the TiO2 surface Equations (7)–(9).

$$TiO\_2 \xleftarrow{hv} h^+ + e^- \tag{7}$$

$$2h^{+} + 2HCO\_{2}^{-} \rightarrow 2CO\_{2} + 2H^{+} \tag{8}$$

$$\text{Cr(VI)} + \text{3e}^- \rightarrow \text{Cr(III)}\tag{9}$$

With this in mind formic acid was added to the reaction mixture prior to TiO2 photocatalytic treatment of Cr(VI).We observed a dramatic enhancement in the reduction rate of Cr(VI), indicating that formic can trap the hole to extend the lifetime of the electron enhancing the rate of Cr(VI) reduction (Figure 11). Since molecular oxygen does not affect the rate it does not appear reduction to superoxide anion radical and subsequent reaction with Cr(VI) change the observed rates of reduction.

**Figure 11.** Effect of formic acid as hole scavenger on Cr(VI) reduction. [Cr (VI)] = 40 μM, [HCOOH] = 10 mM, [TiO2] = 0.10 g/L, 350 nm.

#### **3. Experimental**

#### *3.1. Materials*

Degussa P25 TiO2 (CAS NO. 13463-67-7), a mixture of 80% anatase and 20% rutile with an average surface area of 50 m2 /g, was donated by Degussa (Ridgefield, NJ, USA). Copper(II) nitrate trihydrate (99%–104%), sodium arsenate dibasic heptahydrate (99%) and sodium *meta*-arsenite (98%) were obtained from Sigma (St. Louis, MO, USA), while potassium chromate (99.8%), sodium hydroxide (99.4%), ammonium hydroxide (29.15%), trace metal grade nitric acid (67%–70%) and formic acid (88%) were purchased from Fisher (Waltham, MA, USA). All the chemicals were used without further purification. Millipore filtered water (18 Mކȍ cm) was obtained from a nanopure diamond lab water system (Barnstead Thermolyne Corporation, Dubuque, IA, USA) at room temperature. Volumetric glasswares were used to prepare all solutions.

#### *3.2. Sample Preparation and Analysis*

The concentration of TiO2 was 0.10 g/L, and the initial concentration of Cr(VI) was 40 μmol/L unless otherwise stated. As(III), As(V) and/or Cu(II) were added into TiO2 suspension based on experimental design. One hundred mL of TiO2 suspension was subject to an ultrasonic bath for

15 minutes to achieve a homogeneous suspension of the catalyst in the reaction vessel (Pyrex tube 12 × 1 in, 160 mL capacity, with a vented Teflon screw top). The suspension was magnetically stirred for 1.0 hour in the dark to allow equilibrium adsorption between target compound and TiO2. The solution pH was adjusted with 0.1 M HNO3 and 0.1 M NaOH and measured using a calibrated Pinnacle 530 pH meter (Corning, Vernon Hills, IL, USA).The solution was gently purged with the desired gas (air, oxygen or argon) for 15 min prior to and during irradiation. Irradiation of TiO2 suspension was conducted in a Rayonet photochemical reactor (model RPR-100, Southern New England Ultraviolet, Branford, Connecticut, USA), equipped with a cooling fan and 15 phosphor coated low-pressure mercury lamps (Ȝmax = 350 nm, light intensity = 5.2 ± 0.1 × 106 photon/s/cm3 ). Five mL samples were taken at each specified time intervals, filtered through a 0.45 ȝm PTFE filter and subsequently analyzed.

The total copper and chromium were measured using an Analyst 600 atomic absorption spectrophotometer (Perkin–Elmer, Waltham, MA, USA) at 324.8 nm and 357.9 nm as recommended by the manufacturer. Determination of total arsenic was conducted using inductively coupled plasma mass spectroscopy (ICP-MS, HP 4500, Agilent, Santa Clara, CA, USA). The plasma and auxiliary gas flow rates of the ICP-MS were maintained at 15.4 and 1.0 L/min, respectively. Arsenic speciation of arsenate and arsenite and Cr(VI) were performed using a high-performance liquid chromatograph (HPLC) instrument equipped with a Lab Alliance series III digital pump (Fishersci, Waltham, MA, USA) and an ion exchange column coupled to ICP-MS detection. A PRP X-100 (250 mm × 4.6 mm, 10 ȝm particle size) anion-exchange column(Hamilton, North Quincy, MA, USA) was used to separate Cr(VI) and arsenic species with the mobile phase of 40 mM (pH 9.0) ammonium nitrate at the flow rate of 1.0 mL/min.

#### **4. Conclusions**

TiO2 photocatalysis is effective for the complete reduction of Cr(VI) to Cr(III) in the presence and absence of Cu(II) and As(V). The reduction process is effective over a range of solution pH and under oxygen, air, or argon saturated conditions. The pH effects indicate that the reduction is favorable under acidic solution conditions due to enhanced adsorption through electrostatic attraction between positively charged TiO2 surface and anionic chromate species. The addition of As(V) in the reaction mixture slightly reduces the reduction rate of Cr(VI) which is assigned to competitive adsorption between As(V) and Cr(VI) and competition for reduction processes since As(V) is not reduced under the experimental conditions. Although Cu(II) can be reduced during TiO2 photocatalysis, we observe no reduction of Cu(II) and a slight enhancement in Cr(VI) reduction under very specific conditions. The effective reduction of Cr(VI) is achieved in the presence of As(V) and Cu(II) at different ratios. The addition of formic acid to the reaction solution shows a significant acceleration in the reduction of Cr(VI). Our study clearly demonstrates UV/TiO2 photocatalysis is a promising single treatment process for the remediation of Cr(VI) mixed wastes under a variety of conditions.

#### **Acknowledgments**

KEO and DDD gratefully acknowledge the National Science Foundation for partial support of the project (Grant # CBET–1235803).

#### **Author Contributions**

Yong Cai, Dionysios D. Dionysiou, and Kevin E. O'Shea were critical to the conception, design, oversight of and data analysis for the project. Shan Zheng did the majority of the experimental work and provided a report of the results. Wenjun Jiang and Mamun Rashid ran follow-up experiments and revised the manuscript.

#### **Conflicts of Interest**

The authors declare no conflict of interest.

#### **References**

*Sample Availability*: Samples of the compounds are not available from the authors.


**7. Technical advances**

Many of the advances that are discussed above are system‐based and involve the perioperative period of patient care. These have had a tremendous impact on patient outcomes in the treatment of PDAC. But of all the modalities involved, surgery remains the only treatment with the potential for cure in patients with localized pancreatic cancer. Significant improve‐ ments in preoperative evaluation and postoperative care have reduced the perioperative morbidity and mortality associated with pancreatectomy. As previously discussed, mortality after PD has dropped significantly and there have also been improvements in long‐term survival rates. In addition to these changes, surgical technique itself is progressing and evolving.

In an evidence‐based systematic review, Wright and Zureikat identified four key elements that have allowed minimally invasive pancreatic surgery to gain momentum: safety, oncologic efficacy, cost, and reproducibility. Even though the evidence available is not the result of randomized controlled trials but instead on case series matched with cohorts undergoing open procedures, morbidity and mortality have been shown to be comparable between minimally invasive (MI) and open techniques. This applies for both PD and DP and encompasses all modalities of MI techniques: laparoscopy, robotic‐assisted surgery, and their institutional variations.

The main concern with the adoption of MI techniques for the treatment of PDAC is undoubt‐ edly oncologic efficacy. A study by Kendrick et al. favored MI technique by demonstrating fewer delays to initiation of adjuvant chemotherapy after laparoscopic PD with similar oncologic survival when compared to that in open procedure. Another study using the National Cancer Data Base demonstrated no difference in oncologic outcomes between laparoscopic and open PD [36]. In the setting of DP cases, Lee and colleagues (reference below) showed similar oncologic outcomes and high rates of R0 resection between open and laparo‐ scopic DP. The mean number of lymph nodes evaluated in the aforementioned series was higher with open DP (15.4) when compared with the minimally invasive techniques (10.4 with laparoscopy and 12 with robotic approach). However, there was no statistically significant difference in the number of positive lymph nodes evaluated. Although the retrospective design of these studies introduces the possibility of selection bias in terms of patient selection, surgeon preference/experience, and preoperative patient and oncologic characteristics, the available evidence so far demonstrates that laparoscopic and robotic approaches to pancreatectomy do not adversely affect oncologic outcomes and add benefits such as decreased EBL and LOS [37– 39]. However, it is important to note that the sources of most of the available literature are high‐ volume centers, which introduces a potential source of bias and reinforces the importance of patient evaluation and treatment at high‐volume centers with multidisciplinary teams.

the study also illustrated a fourfold increase in mortality (3–12%) [35]. This raises skepticism toward findings in the previous literature and supports advocating caution against eliminating the use of drains altogether. However, per ERAS recommendations, early removal of the drain

These strategies provide a unified protocol for perioperative management of the PD procedure that could likely prove beneficial to centers through reducing postoperative complication rates, time of recovery and hospital length of stay [28, 32]. Ultimately, it is the summation of these factors that contribute to the improvement in the postoperative outcomes of pancreatic cancer patients. While the aforementioned concepts and strategies prove significant for the manage‐ ment of the acute surgical patient, the overall management strategy for a pancreatic cancer

Many of the advances that are discussed above are system‐based and involve the perioperative period of patient care. These have had a tremendous impact on patient outcomes in the treatment of PDAC. But of all the modalities involved, surgery remains the only treatment with the potential for cure in patients with localized pancreatic cancer. Significant improve‐ ments in preoperative evaluation and postoperative care have reduced the perioperative morbidity and mortality associated with pancreatectomy. As previously discussed, mortality after PD has dropped significantly and there have also been improvements in long‐term survival rates. In addition to these changes, surgical technique itself is progressing and

In an evidence‐based systematic review, Wright and Zureikat identified four key elements that have allowed minimally invasive pancreatic surgery to gain momentum: safety, oncologic efficacy, cost, and reproducibility. Even though the evidence available is not the result of randomized controlled trials but instead on case series matched with cohorts undergoing open procedures, morbidity and mortality have been shown to be comparable between minimally invasive (MI) and open techniques. This applies for both PD and DP and encompasses all modalities of MI techniques: laparoscopy, robotic‐assisted surgery, and their institutional

The main concern with the adoption of MI techniques for the treatment of PDAC is undoubt‐ edly oncologic efficacy. A study by Kendrick et al. favored MI technique by demonstrating fewer delays to initiation of adjuvant chemotherapy after laparoscopic PD with similar oncologic survival when compared to that in open procedure. Another study using the National Cancer Data Base demonstrated no difference in oncologic outcomes between laparoscopic and open PD [36]. In the setting of DP cases, Lee and colleagues (reference below) showed similar oncologic outcomes and high rates of R0 resection between open and laparo‐ scopic DP. The mean number of lymph nodes evaluated in the aforementioned series was higher with open DP (15.4) when compared with the minimally invasive techniques (10.4 with laparoscopy and 12 with robotic approach). However, there was no statistically significant

is associated with fewer and reduced rate of complications [28, 35].

patient has substantially changed [23, 25, 28, 32].

**7. Technical advances**

170 Challenges in Pancreatic Pathology

evolving.

variations.

Cost is one of the limitations of MI pancreatectomy, particularly the robotic technique. However, some authors have shown the robotic technique to be cost effective when the reduction in length of stay is taken into consideration [40, 41]. Additionally, the robotic technical skills are potentially easier to acquire when compared to laparoscopic technique. This is secondary to the advantages provided by stereotactic vision, robotic simulators, and training consoles. The learning curve defined as 80 cases for a reduction in operative time may shorten with time since the operative steps and training techniques have recently become betterdefined [42].

Another noteworthy technical advancement is the incorporation of vascular resection (VR) with PD. Tseng et al. described five types of venous resection and reconstruction involving the superior mesenteric vein (SMV), portal vein (PV), or superior mesenteric‐portal venous (SMPV) confluence. These are tangential resection with saphenous vein patch (V1), segmental resection with splenic vein ligation and primary anastomosis (V2) or with interposition graft (V3), segmental resection without splenic vein ligation and primary anastomosis (V4) or with interposition graft (V5). In their single institution series, Tseng and colleagues demonstrated that properly selected patients with PDAC of the head of the pancreas undergoing VR had a median survival of approximately two years. There was no statistical difference between survival of patients undergoing standard PD and those undergoing PD and VR (*p* = 0.177) [43].

Adequate patient selection for PD with VR has been possible by technological advances in computer tomography and by a multidisciplinary approach involving surgeons and radiol‐ ogists. While several single center studies [44–46] have demonstrated PD with VR to be safe, a retrospective cohort analysis of the National Surgical Quality Improvement Program database demonstrated increased postoperative morbidity and mortality with the inclusion of venous resection [47]. This difference can be attributed to publication bias since most of the previously published single center studies have been from high‐volume centers. Based on this, PD with VR in carefully selected patients at high‐volume institutions opens up the possibility of survival comparable to that of patients undergoing standard PD, even in the setting of an increased frequency of R1 resections in patients that require VR [43].

Not only has surgical technique evolved but also, operative standards of care have been improved. It is known that lymph node metastasis is a poor prognostic factor for PDAC of the pancreatic head. The retrieval of an adequate number of lymph nodes or total lymph nodes examined (TNLE) is a measure of quality of care. Not only does it lead to optimal locoregional control but also, it is of upmost importance for pathological staging. Current NCCN guidelines recommend that at least 11 lymph nodes are retrieved and examined. Gleisner and colleagues showed an association between TNLE and overall survival, but the association was not uniform through time at their institution. Standards of care improved. We have found that less than 12 lymph nodes are inadequate lymphadenectomy [48].


**4. MFGM as key strategy in infant food (IF) formulation**

In recent decades, formulations of infant and neonatal foods have introduced several new components and modifications to enhance its functional health performance to mimic human milk. Major changes in the IF that has been successfully introduced are supplementation of prebiotics (FOS and GOS) [27, 28], probiotics [29–31], docosahexaenoic acid (DHA) and arachidonic acid (ARA) [32], meat protein [33], plant protein (pea and soy protein) [34], taurine [35], MFGM [7, 36], polyamines [37, 38], folates [39] and osteopontin [40]. Even though many of these modifications are being carried out, very little knowledge is known to us on human milk's minor bioactive compounds that are essential for the neonatal development on long and short term studies.

Sometimes, supplementation of IF with bioactive compounds as same in human milk can cause adverse effects on infant growth and nutrition. Example, addition of opioid protein (beta-casomorphin) in IF can cause life threatening events due to its exogenous nature. Adaptation of infants and biosimulation of metabolic activities in infant digestion can be responsible for this condition [41]. Still now the regulation on fortification or supplementation of bioactive compounds in IF and nutrition was not standardized globally. However, fortification of MFGM was profitably done and studied for their effect on health benefits in many infants. Animal and human studies of commercially available MFGM formula and their outcomes are tabulated in **Table 2**.


**4. Animal-assisted therapy in occupational therapy**

#### **4.1. The role of animal-assisted approaches in rehabilitation**

AAT is used as a therapeutic approach in rehabilitation. AAT approaches are being used all over the world in order to improve not only the emotional and psychosocial states but also the physical, sensory, and cognitive skills positively for individuals with various diseases or of different ages [37, 38]. Rehabilitation practices include holistic approaches, with divergence toward children, adolescents, adults, and elderly people.

It is known that there are many neurological, physiological, and genetic diseases seen in children, and the rehabilitation practices are widely used in these children [39]. In literature, AAT is commonly used in children with cerebral palsy, developmental neurological disorders, autism spectrum disorders, sensory processing disorders, degenerative neurological and muscle disorders that mainly focus on control of muscle tonus, mobility, and balance [40]. When the elderly and adult population rehabilitation applications are examined, it is seen that animal-assisted approaches are preferred in the treatment of diseases such as multiple sclerosis, head trauma, post-traumatic neurological conditions, Alzheimer Disease, dementia, anxiety, and depression [41–43]. These diseases can cause a reduction in postural symmetry and control, and deterioration in cognitive skills like attention, memory, and executive functions [37].

All of these patients with diseases, whether young or old, were psychologically affected, and their motivation decreased during rehabilitation. It is known that sensory, emotional, and physical characteristics of animals can be utilized to increase the level of motivation in rehabilitation. In fact, in most developed countries today, health-care providers employ animal-assisted therapy in a wide range of settings, including rehabilitation centers, acute care, psychiatric centers, and outpatient clinics. For example, doctors' consulting rooms have fish tanks in their waiting rooms to promote a sense of calm [44]. It is now well known that the presence of animals can induce relaxation, increase positive emotions, reduce resistance to treatment, and put patients' minds at ease.

Awareness of the advantages and disadvantages of the animals and species used by the professional practitioner team in rehabilitation practices involving many health disciplines involved in this area positively affect the effectiveness of rehabilitation [6]. At the same time, it also emphasizes the importance of knowing the animal's unique structure and instincts in these studies [6, 37]. Most studies and programs in AAT utilize animals such as livestocks, dolphins, dogs, cats, birds, hamsters, or horses [45]. All animals have certain advantages and disadvantages within themselves, so that the practitioner can make arrangements according to the individual and individual's needs.

## *4.1.1. Therapy with livestock*

improvements in physiological parameters, such as heart rate and blood pressure. On the other hand, pets serving as a source of social support seem to provide a relatively high level of evidence for the longer-term benefits of animal companionship [31].Cobb has defined social support as "relationships that direct, to emphasize and give importance to, to describe that it is the pattern of mutual obligations." However, the newer authors have expressed it as "perceived social support" and "social networking" characteristics. The first represents a qualitative definition of the degree of satisfaction from the support that one receives from certain social relations; the second is a more quantitative measure involving the number, frequency, and propensity of the person's general social interactions [32]. However, the importance of social support to human well-being, which we wanted to describe, has been regarded as one of the top-down issues throughout history. Loneliness—lack of social support—has always been seen as a painful and distasteful phenomenon; since ancient times, societies have used single-cell imprisonment, exile, and social mobilization as methods of punishment. This, in fact, shows that loneliness is actually the basic punishment method. In addition, religious themes explain in detail the psychological effects of autobiographical, social isolation that homeland traitors and prisoners of war wrote. Many of them describe physical torture in a way that will emotionally, often sharply, up to the apex of gradual descent. This decrease in pain is associated with the onset of a serious indifference and hopelessness, which usually requires catatonic deprivation [29]. In the last 10–15 years, a comprehensive medical literature has emerged confirming that there is a strong and positive link between social support and improved human health and survival [33–35]. There is a great deal of social support in reducing the adverse effects of stress, which chronic life has brought. With the controversy still underestimating these effects, many authorities now accept the judgment that the main benefits arise from the buffering or healing capacities of long-term effects of supporting social relations [36]. Theoretically, this beneficial effect of social support should be applied to any positive social association. It has been observed that positive behaviors are exhibited within the two parties in relation to which one is loved or respected. Despite the increasing evidence for anthro-zoological research in the recent past, the idea that animal attendants contribute

96 Occupational Therapy - Therapeutic and Creative Use of Activity

socially to human health, however, received very limited medical attention [8].

AAT is used as a therapeutic approach in rehabilitation. AAT approaches are being used all over the world in order to improve not only the emotional and psychosocial states but also the physical, sensory, and cognitive skills positively for individuals with various diseases or of different ages [37, 38]. Rehabilitation practices include holistic approaches, with divergence

It is known that there are many neurological, physiological, and genetic diseases seen in children, and the rehabilitation practices are widely used in these children [39]. In literature, AAT is commonly used in children with cerebral palsy, developmental neurological disorders,

**4. Animal-assisted therapy in occupational therapy**

**4.1. The role of animal-assisted approaches in rehabilitation**

toward children, adolescents, adults, and elderly people.

It is mentioned in the literature that all farm animals can be easily included in treatment approaches as long as they are checked by the veterinarian for good health and reliability. The benefits and difficulties of incorporating livestock into therapy approaches may vary according to the therapist's rehabilitation goal. These animals are preferred by the occupational therapists (OTs) in rehabilitation applications, in particular for those individuals who have difficulty in independent daily living skills, in terms of a large living space, and special need for care. There are also studies showing that AAT with livestock affects individuals' motor and cognitive functions positively [46, 47]. They are preferred by OTs because they can help improve their equilibrium, hand-eye coordination, executive function, and hand skills of individual.


Preface

When multiple analog or digital signals are combined into one signal over a shared medium, it is called multiplexing or muxing. This is a well-known method in telecommunications and computer networking. It is widely applied in communication systems and the aim is to share a scarce resource, for example, a wire or optic fiber cable for telecommunication applications. The reverse process is necessary on the receiver's end to extract the information sent.

This book presents recent applications and advancements in multiplexing (MUX) and de-multiplexing (DEMUX) in optic and wireless communication applications. It examines signals and waveforms from different points of view for both orthogonal and non-orthogonal subcarrier scenarios.

I wish to acknowledge my late father. I hope this book makes him proud. I also wish to thank my mentors Prof. Max Ammann from the Technological University Dublin (TU Dublin) and Prof. Daniel Kilper from Trinity College Dublin (TCD) who helped me immensely in the last two years.

I acknowledge this publication is associated with CONNECT - the Science Foundation Ireland Research Centre for Future Networks and Communications and SFI Centre for Research Training in Advanced Networks for Sustainable Societies (ADVANCE CRT), Dublin, Ireland.

> **Somayeh Mohammady** School of Electrical and Electronic Engineering, Technological University Dublin (TUDublin), Dublin, Ireland

Section 1


**1. Introduction**

258 Studies on Water Management Issues

Kuhnle, R.A., Simon, A., and Knight, S.S. (2001). "Developing linkages between sediment

Milliman, J.D. and Meade, R.H. (1983). World-wide delivery of river sediment to the oceans.

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Smith, V.H. and Schindler, D.W. (2009). "Eutrophication science: where do we go from

USBR (U.S. Bureau of Reclamation) 2006, *Erosion and sedimentation manual*, U.S. Department

White, R. (2001). Evacuation of sediments from reservoirs. Thomas Telford,<PHONE_NUMBER>,

Yang M., Yu J.W., Li Z.L. Guo Z.H., Burch M. and Lin T.F. (2008). "Taihu Lake Not to blame

Yang, S.Q. (2004). The Global and China's water crisis and solutions in the 21st century.

Yang, S.Q. and Liu P.W. (2010). "Strategy of water pollution prevention in Taihu Lake and

Zhang J. (1995), Geochemistry of trace metals from Chinese river/estuary systems: an

Tianjing Univ. Press, 7-5618-2069-0, Tianjing, China (in Chinese).

its effects analysis". *J. Great Lake Research*, 36(1), 150-158.

Lake Biwa tributaries, Japan". *Science of the Total Envir.*, 389, 132-148. Newcombe, C.P. and Jensen, J.O.T. (1996). "Channel suspended sediment and fisheries: a

Measuremen. *Advances in Earth Scienc*. 22(9): 896-906 (in Chinese).

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overview. *Estuar Coast Shelf Sci*; 41:631–58.

here?". *Trends Ecol Evol*. 24(4): 201-7.

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*J. Geol*., 91, 1-21;

42059-2, Tokyo.

525-544.

London.

load and biological impairment for clean sediment TMDLs". Wetlands Engineering

discharge to the ocean: the importantnce of small mountainous rivers. *J. Geol*., 100,

*Ecosystems of the world: Lakes and Reservoirs*, Taub, F.B., 303-329. Elsevier, 0-444-

Tanaka, T., Wada, E., Yachi, S. (2008). "Effect of agriculture on water quality of

synthesis for quantitative assessment of risk and impact". North American Journal

Caused by Eutrophication and Cyanobacterial Bloom in Lake Taihu: Cause and

of the Interior, Bureau of Reclamation, Technical Service Center, Sedimentation and

Based on the monitoring data and climate projections, scientists highly agree that freshwater resources are vulnerable and have the potential to be strongly impacted by climate change in the long-run. However, there is no consensus about the degree of impact of human activities on climate change. Using simulation techniques, Intergovernmental Panel for Climate Change (IPCC) estimates the expected changes in the climate on a global scale for different emission scenarios. The results from global estimations are used to drive other simulations that run on regional scaled smaller domains at higher spatial resolution.

Assuming that climate change scenarios will be realized in the future, it is possible to foresee that there will be effects of climate change on watershed ecology and on the water resources. Considering only two of the climate change related variables; temperature and precipitation one can conclude that

This chapter is devoted to the impacts of climate change on freshwater resources; their availability, quality, quantity, uses and management is evaluated. Impacts on ecology are mentioned. Several management alternatives to reduce the potential adverse effects of climate change are identified; merits and tradeoffs involved are discussed. The discussions on this chapter is about what the ecological impacts of climate change on aquatic ecosystems and water resources will be and what precautions can be taken to sustain watershed ecosystems and water resources together with the demands of our socioeconomic system rather than "how we can prevent the climate change".

Managing the Effects of the Climate Change on Water Resources and Watershed Ecology 261

indicated that without any limitations in human activities related to industrial emissions, 1.8ºC of global temperature increase and 6 – 30 cm sea level rise may be expected 2030 taking the beginning of the industrial revolution (second half of the 18th century) as

Intergovernmental Panel on Climate Change (IPCC, 2007) refers in the Fourth Assessment Report, AR4, to the warming of the global climate system and states that "most of the observed increase in globally averaged temperatures since the mid-20th century is very likely [this likelihood statement can be interpreted as probability in excess of 90%; comment added] due to the observed increase in anthropogenic greenhouse gas concentrations" (Szwed et al., 2010). It is also expressed that on the global average, surface temperatures have in¬creased by about 0.74°C between years 1906 and 2005 during which the warming has not been steady and not kept the same both temporally and spatially (IPCC, 2007). According to the recordings taken since 1901 only a few areas have been cooled, among which one of the most notable one is the northern North Atlantic near southern Greenland. However, during this period warming has been experienced more over the continental interiors of Asia and northern North America. As referred by IPCC (2007), the most evident warming signal has occurred in parts of the middle and lower latitudes whereas the duration of the frost-free season has increased in most mid- and high-latitude regions of both hemispheres. Besides, most mountain glaciers and ice caps have been shrinking since

Observations so far indicate that over most land areas, cold days and nights have got warmer and fewer, while hot days and nights have got warmer and more frequent. Area affected by drought has been increased. This trend is expected to continue in the future.

The effects of climate change have been highly sensed in sectors like agriculture, energy and water related applications. As stated by Szwed et al., (2010), agriculture in the northern Europe has been temperature-restricted, while in the south it has been water-restricted. Both conditions may have lead to decrease in the crop yields and require the selection of new irrigation techniques, new crop patterns etc. for the sustainability of agricultural production. Water-related studies frequently mention that water budgets may become increasingly stressed. High evapotranspiration and low precipitation in summer leads to depletion of the

Moreover, researches and model-based studies indicate that weather-related extremes are expected to get more frequent and/or more severe and coping with these events will become more difficult. Countries facing such conditions are attempting to take mitigation

Data related to climate change are on two different temporal scales. The first of these data is the so-called paleoclimatological data that is indirect. Stable isotope data dating back hundreds thousands of years back is used to reconstruct the past atmospheric composition and basic atmospheric conditions such as temperature, precipitation. The second type of data is the historical data from observations dating approximately two centuries back at most. Long term

time series of meteorological data can be used to analyse the recent climate dynamics.

measures and develop national and/or regional adaptation strategies.

**2. Simple methods to quantify the climate change**

reference.

1850s.

water storage.

**2.1 Data**


**7. Results and discussion**

Controlled volumes of pristine MWNT solutions were dropped on SERS active substrates, the SERS spectra acquired in different spatial positions, maintaining all the experimental parameters unchanged are reported in **Figure 5**.

The diameter of SWNTs can be calculated from the frequency of corresponding RBM, through the Bandow relation [13–15]. Since the RBM intensity strongly decreases when the tube diameter

**Figure 6.** (a) HR-SEM image of pristine MWNT film deposited on SERS substrate. (b) Magnified view of region with larger thickness layer (c) Magnified view of region with thinner layer. The leaning effect of nanopillars is evidenced.

**Figure 5.** SERS spectra of pristine MWNT dried film. The MWNT layer thickness is decreasing from spectrum (a) to (c).

Surface-Enhanced Raman Spectroscopy Characterization of Pristine and Functionalized Carbon…

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211

The SERS trace (a) has no significant differences in comparison of that reported in **Figure 1**, if one excepts the amplification of the signal whereas curves (b) and (c) show variations in some Raman line intensities, line shape and appearance of several sharp peaks, in the frequency range 400–1100 cm−1, characteristics of C60-like molecules [25].

We observed a gradual increase of the D band, which indicates an enhanced degree of disorder, with a concomitant modification of the G band profile, consisting in a peak splitting due to the increase of D' band at its high energy side. The peak at about 250 cm−1 in the SERS curves (b) and (c) is similar to that at 171 cm−1 in Raman spectrum of SWNTs, reported in **Figure 1**.

The RBMs are not often observed in MWNTs, its observation in SERS trace is consistent with the fact that for a molecule adsorbed on a nano-structured surface, the modes which involve atoms vibrating perpendicularly to the surface are more enhanced than the others [26]. However, the observed RBM width (45 cm−1) is larger than that measured in the SWNT Raman spectra [16, 17].

This finding can be explained considering that in a MWNT also the radial vibrations of outer shells contribute to this mode, producing a number of overlapping RBM peaks larger than those expected for SWNTs with the same distribution of diameter [18].

Surface-Enhanced Raman Spectroscopy Characterization of Pristine and Functionalized Carbon… http://dx.doi.org/10.5772/intechopen.74065 211

**6. Raman spectrometers**

210 Raman Spectroscopy

400–3000 cm−1, acquisition time 10 s).

eters unchanged are reported in **Figure 5**.

range 400–1100 cm−1, characteristics of C60-like molecules [25].

**7. Results and discussion**

Raman spectra [16, 17].

In the first steps of our works, we acquired SERS and Raman spectra using a Raman spectrometer BwTek (i-Raman 785.), equipped with a micro-positioning system for fine xyz adjustments and a video camera for sampling viewing. The system uses an air-cooled charge coupled device (CCD) detector. The 785 nm laser light, to guarantee the coupling with gold plasmons, was focused onto the sample using a 20× objective (corresponding to a laser beam diameter of 90 μm, as already mentioned). Samples were moved into position using the xyz translational stage. The Raman spectra were acquired in the wavelength range 789–1048 nm

Raman mapping was performed with a high-resolution micro-Raman spectrometer (Horiba Xplora) with 785 nm excitation wavelength. The Raman signal was collected through a 100× objective in the range 100–2000 cm−1 with accumulation time of 10 s per spectrum. Areas of the substrates up to 10 × 10 μm were scanned with an acquisition grid of 0.6 and 0.8 μm step size in x and y, respectively. All the spectra were obtained with 100 μW laser power, to avoid sample heating and damaging. The SERS maps were obtained analyzing the peak intensity of every spectrum. Raman spectra were also acquired with 532 nm excitation (range

Controlled volumes of pristine MWNT solutions were dropped on SERS active substrates, the SERS spectra acquired in different spatial positions, maintaining all the experimental param-

The SERS trace (a) has no significant differences in comparison of that reported in **Figure 1**, if one excepts the amplification of the signal whereas curves (b) and (c) show variations in some Raman line intensities, line shape and appearance of several sharp peaks, in the frequency

We observed a gradual increase of the D band, which indicates an enhanced degree of disorder, with a concomitant modification of the G band profile, consisting in a peak splitting due to the increase of D' band at its high energy side. The peak at about 250 cm−1 in the SERS curves (b) and (c) is similar to that at 171 cm−1 in Raman spectrum of SWNTs, reported in **Figure 1**.

The RBMs are not often observed in MWNTs, its observation in SERS trace is consistent with the fact that for a molecule adsorbed on a nano-structured surface, the modes which involve atoms vibrating perpendicularly to the surface are more enhanced than the others [26]. However, the observed RBM width (45 cm−1) is larger than that measured in the SWNT

This finding can be explained considering that in a MWNT also the radial vibrations of outer shells contribute to this mode, producing a number of overlapping RBM peaks larger than

those expected for SWNTs with the same distribution of diameter [18].

corresponding to Raman shifts of 75–3200 cm−1 (resolution better than 3 cm−1).

**Figure 5.** SERS spectra of pristine MWNT dried film. The MWNT layer thickness is decreasing from spectrum (a) to (c).

The diameter of SWNTs can be calculated from the frequency of corresponding RBM, through the Bandow relation [13–15]. Since the RBM intensity strongly decreases when the tube diameter

**Figure 6.** (a) HR-SEM image of pristine MWNT film deposited on SERS substrate. (b) Magnified view of region with larger thickness layer (c) Magnified view of region with thinner layer. The leaning effect of nanopillars is evidenced.

increases, we can roughly estimate the inner diameter of MWNTs from their RBMs in the SERS spectra by using the same rule. The RBM at 250 cm−1 corresponds to an inner tube diameter of 0.8 nm. These values are compatible with those reported in the data sheet of MWNTs from the manufacturer.

**Figure 6** presents a HRSEM view, taken at different magnification of pristine MWNT films. The MWNTs are tightly interlaced forming a web of filaments that are distributed across the SERS active surface, occupying the regions with highest Raman signal amplification as the space between the nano-pillars. However, the layer thickness is not uniform across the deposited patch and this is reflected in the observed differences between the SERS spectra reported in **Figure 5**.

In fact, these variations can be interpreted by considering the breaking of the nanotubes into species such as amorphous carbon, tubular fragments, and closed shell fullerenes. Such reactions are of chemical nature occurring at the nanotube metal substrate interface.

**Figure 7** illustrates the comparison between the Raman spectra of pristine and covalently functionalized MWNTs. The carboxyl functionalization was performed by a reflux in sulfuric/nitric acid (Nanolab, average diameter = 30 nm, length 1–5 μm, from now on denoted as COOH-MWNTs). This process leads to the concentration of COOH groups on the nanotube surface. By reacting the carboxylate CNTs with ethylene diamine, nanotubes with amide linkage and a primary amine group at the end of carbon chain are obtained (Nanolab, average diameter = 15 nm, length 1–5 μm, from now on denoted as NH2 -MWNTs). However, in the Raman spectra of covalently functionalized vibrational modes that can be directly related to molecular groups are not observed.

As a consequence, the use of Raman spectroscopy to study the structure of functionalized CNTs is routinely limited to the evaluation of the ID/IG ratio, since the interaction between carbon nanotube wall and functional groups is expected to produce a higher density of sp3

Surface-Enhanced Raman Spectroscopy Characterization of Pristine and Functionalized Carbon…

However, when a set of spectra is recorded from the same pristine CNTs sample, we frequently observed a variation in the ID/IG ratio, up to the 15% of its average value, which is sometimes apparently of the same order as that recorded after the chemical functionalization. Although a more efficient discrimination can be reached by applying the principal component analysis [30], the observation of Raman spectral changes induced by the chemical func-

In **Figure 8** are illustrated the different morphologies of functionalized MWNT-dried films.

of filaments. Differently, the drying of COOH-MWNT solution forms a very thin layer with

We acquired the SERS spectra from functionalized MWNT films in different spatial positions, maintaining all the experimental parameters unchanged obtaining reproducible spectra,

In addition to the signal enhancement, compared to conventional Raman spectra, the SERS traces show sharp peaks in wavenumber region ascribable to vibrations of molecular groups;

http://dx.doi.org/10.5772/intechopen.74065

213

hybridized carbon sites, with consequent increase of ID/IG ratio [27–29].

view of region (a); (d) magnified view of region (b) evidencing the formation of a dense layer.

tionalization is challenging.

shown in **Figure 9**.

Due to the small outer diameter, the NH2

**Figure 8.** HR-SEM images of (a) COOH-MWNT and (b) NH2

some groups of few isolated nano-tubes.

**Figure 7.** Raman spectra of MWNT mat. (a) Raman spectrum acquired from pristine MWNT film, ID/IG = 0.8; (b) Raman spectrum acquired from COOH-functionalized MWNTs, ID/IG = 1.2; (c) Raman spectrum acquired from NH2 functionalized MWNTs, ID/IG = 1.4.

increases, we can roughly estimate the inner diameter of MWNTs from their RBMs in the SERS spectra by using the same rule. The RBM at 250 cm−1 corresponds to an inner tube diameter of 0.8 nm. These values are compatible with those reported in the data sheet of MWNTs

**Figure 6** presents a HRSEM view, taken at different magnification of pristine MWNT films. The MWNTs are tightly interlaced forming a web of filaments that are distributed across the SERS active surface, occupying the regions with highest Raman signal amplification as the space between the nano-pillars. However, the layer thickness is not uniform across the deposited patch and this is reflected in the observed differences between the SERS spectra reported in **Figure 5**. In fact, these variations can be interpreted by considering the breaking of the nanotubes into species such as amorphous carbon, tubular fragments, and closed shell fullerenes. Such reac-

**Figure 7** illustrates the comparison between the Raman spectra of pristine and covalently functionalized MWNTs. The carboxyl functionalization was performed by a reflux in sulfuric/nitric acid (Nanolab, average diameter = 30 nm, length 1–5 μm, from now on denoted as COOH-MWNTs). This process leads to the concentration of COOH groups on the nanotube surface. By reacting the carboxylate CNTs with ethylene diamine, nanotubes with amide linkage and a primary amine group at the end of carbon chain are obtained (Nanolab, average

Raman spectra of covalently functionalized vibrational modes that can be directly related to

**Figure 7.** Raman spectra of MWNT mat. (a) Raman spectrum acquired from pristine MWNT film, ID/IG = 0.8; (b) Raman spectrum acquired from COOH-functionalized MWNTs, ID/IG = 1.2; (c) Raman spectrum acquired from NH2

tions are of chemical nature occurring at the nanotube metal substrate interface.

diameter = 15 nm, length 1–5 μm, from now on denoted as NH2

molecular groups are not observed.

functionalized MWNTs, ID/IG = 1.4.

from the manufacturer.

212 Raman Spectroscopy

**Figure 8.** HR-SEM images of (a) COOH-MWNT and (b) NH2 -MWNT films deposited on SERS substrate; (c) magnified view of region (a); (d) magnified view of region (b) evidencing the formation of a dense layer.

As a consequence, the use of Raman spectroscopy to study the structure of functionalized CNTs is routinely limited to the evaluation of the ID/IG ratio, since the interaction between carbon nanotube wall and functional groups is expected to produce a higher density of sp3 hybridized carbon sites, with consequent increase of ID/IG ratio [27–29].

However, when a set of spectra is recorded from the same pristine CNTs sample, we frequently observed a variation in the ID/IG ratio, up to the 15% of its average value, which is sometimes apparently of the same order as that recorded after the chemical functionalization. Although a more efficient discrimination can be reached by applying the principal component analysis [30], the observation of Raman spectral changes induced by the chemical functionalization is challenging.

In **Figure 8** are illustrated the different morphologies of functionalized MWNT-dried films. Due to the small outer diameter, the NH2 -MWNTs are tightly interlaced forming a dense web of filaments. Differently, the drying of COOH-MWNT solution forms a very thin layer with some groups of few isolated nano-tubes.

We acquired the SERS spectra from functionalized MWNT films in different spatial positions, maintaining all the experimental parameters unchanged obtaining reproducible spectra, shown in **Figure 9**.

In addition to the signal enhancement, compared to conventional Raman spectra, the SERS traces show sharp peaks in wavenumber region ascribable to vibrations of molecular groups;

structural defects. It is worth to note that because there is no shift between SERS bands and the corresponding ones in the Raman spectrum, the interaction between MWNTs and the

We can note also that in the SERS spectra of functionalized MWNTs, shoulders of G band at

the presence of the latter peak could be ascribed to the combination of N-H bend and C-N stretch, since these bands appear in both functionalized samples, they were assigned to disor-

rings and rings with other orders, whereas the higher frequency peak, was often recorded in amorphous hydrogenated carbon, due to the C─C bond strain caused by the formation of

Surprisingly, also in the SERS spectra of pristine graphene, we recorded a large number of sharp peaks belonging to molecular group vibrations, as illustrated in **Figure 10**: namely C─C═O bending (520–570 cm−1), C─O─C deformation, (850 cm−1), O─H (900–960 cm−1) and

Functional groups as ethers, carbonyls, carboxyls, and hydroxyls are likely retained in the graphene structure, as a consequence of chemical exfoliation process and the presence of oxygen and hydrogen atoms in few at percentage was confirmed by XPS measurements of

We can also note that close to the G band are present the peaks of disordered carbon already observed in functionalized MWNTs. The presence of disordered carbon peaks in the SERS

**Figure 10.** SERS spectra of pristine graphene. The spectra (a), (b), and (c) were acquired at different scanning positions

bonds. In fact, the peak at 1510 cm−1 was observed in carbon with sixfold

Surface-Enhanced Raman Spectroscopy Characterization of Pristine and Functionalized Carbon…

215

http://dx.doi.org/10.5772/intechopen.74065

1510 and 1544 cm−1 are clearly distinguishable. Although in the SERS trace of NH2

(1040 cm−1) bending, and C─C(O)─C stretching 1180–1270 cm−1) [31, 34].

active surface is physical.

dered carbon with sp3

manufacturer [35].

across the dried film.

CH2

C─H covalent bonds [6, 7, 9, 11, 33].

**Figure 9.** SERS spectra of pristine (a), COOH-MWNTs (b), and NH2 -MWNTs (c).

namely the C─O─C stretching (shoulder at around 1260 cm−1), CH3 deformation (1320 cm−1), C─N stretching (1240 cm−1, 1460 cm−1), and C═O stretching at 1730 cm−1 [31, 32]. The presence of these bands proves experimentally the linkage of desired molecular groups to the nanotube walls. It is worth to note that the C═O stretching appears in both covalently functionalized samples owing to the functionalization procedure, which introduces the linkage of amides after that of carboxylate.

In the SERS spectrum of COOH-MWNTs, the D′ band is not distinguishable as shoulder next to the G band, indicating that this sample has a lower amount of defects, as expected for carbon nanotubes with large diameter, which exhibit reduced tip curvature and in turn fewer structural defects. It is worth to note that because there is no shift between SERS bands and the corresponding ones in the Raman spectrum, the interaction between MWNTs and the active surface is physical.

We can note also that in the SERS spectra of functionalized MWNTs, shoulders of G band at 1510 and 1544 cm−1 are clearly distinguishable. Although in the SERS trace of NH2 -MWNTs, the presence of the latter peak could be ascribed to the combination of N-H bend and C-N stretch, since these bands appear in both functionalized samples, they were assigned to disordered carbon with sp3 bonds. In fact, the peak at 1510 cm−1 was observed in carbon with sixfold rings and rings with other orders, whereas the higher frequency peak, was often recorded in amorphous hydrogenated carbon, due to the C─C bond strain caused by the formation of C─H covalent bonds [6, 7, 9, 11, 33].

Surprisingly, also in the SERS spectra of pristine graphene, we recorded a large number of sharp peaks belonging to molecular group vibrations, as illustrated in **Figure 10**: namely C─C═O bending (520–570 cm−1), C─O─C deformation, (850 cm−1), O─H (900–960 cm−1) and CH2 (1040 cm−1) bending, and C─C(O)─C stretching 1180–1270 cm−1) [31, 34].

Functional groups as ethers, carbonyls, carboxyls, and hydroxyls are likely retained in the graphene structure, as a consequence of chemical exfoliation process and the presence of oxygen and hydrogen atoms in few at percentage was confirmed by XPS measurements of manufacturer [35].

We can also note that close to the G band are present the peaks of disordered carbon already observed in functionalized MWNTs. The presence of disordered carbon peaks in the SERS

**Figure 9.** SERS spectra of pristine (a), COOH-MWNTs (b), and NH2

after that of carboxylate.

214 Raman Spectroscopy

namely the C─O─C stretching (shoulder at around 1260 cm−1), CH3

C─N stretching (1240 cm−1, 1460 cm−1), and C═O stretching at 1730 cm−1 [31, 32]. The presence of these bands proves experimentally the linkage of desired molecular groups to the nanotube walls. It is worth to note that the C═O stretching appears in both covalently functionalized samples owing to the functionalization procedure, which introduces the linkage of amides

In the SERS spectrum of COOH-MWNTs, the D′ band is not distinguishable as shoulder next to the G band, indicating that this sample has a lower amount of defects, as expected for carbon nanotubes with large diameter, which exhibit reduced tip curvature and in turn fewer

deformation (1320 cm−1),

**Figure 10.** SERS spectra of pristine graphene. The spectra (a), (b), and (c) were acquired at different scanning positions across the dried film.

spectra of graphene and functionalized MWNTs is a further proof of evidence of the formation of tetrahedrally coordinated bonds between carbon atoms and molecular groups.

**8. Conclusions and outlook**

**Author details**

Sabina Botti1

Denmark

**References**

the distribution of functional groups across the scanned area.

\*, Alessandro Rufoloni1

\*Address all correspondence to<EMAIL_ADDRESS>
1 Fusion and Nuclear Security Department, ENEA, Frascati, Italy

Nanotechnology. 2008;**3**:387-394. DOI: 10.1038/nano.2008.135

Analytical Chemistry. 2005;**77**:338A-346A and references therein

posites. Advanced Materials. 2010;**22**:1672-1688

Electroanalytical Chemistry. 1977;**84**:1-20

izing groups either of synthesis process of graphene as chemical exfoliation.

In summary, we performed SERS measurements on graphene pristine and functionalized MWNTS and graphene nano-structured film deposited on gold-coated Si nano-pillar substrates. The strong surface enhancement effect allowed us to record the Raman signal from functional molecules that are not recorded in conventional Raman spectra proving experimentally their linkages to the CNT walls and graphene edges. By using the relative intensities of specific SERS features as contrast parameters to obtain SERS maps, it is possible to study

Surface-Enhanced Raman Spectroscopy Characterization of Pristine and Functionalized Carbon…

The obtained results encourage us to consider SERS as a powerful method to obtain a rapid monitor either of the procedures used to interface graphene and nanotubes with functional-

, Tomas Rindzevicius2

2 Department of Micro and Nanotechnology, Technical University of Denmark, Lyngby,

[1] Hersam MC. Progress towards monodisperse single-walled carbon nanotubes. Nature

[2] Byrne MT, Gun'ko YK. Recent advances in research on carbon nanotube-polymer com-

[3] Kim SW, Kim T, Kim YS, Choi HS, Lim HJ, Yang SJ, Park CR. Surface modifications for the effective dispersion of carbon nanotubes in solvents and polymers. Carbon. 2012;**50**:3-33

[4] Jeanmaire DL, Van Duyne RP. Surface Raman spectro-electrochemistry. Journal of

[5] Haynes CL, McFarland AD, Van Duyne RP, Surface-enhanced Raman spectroscopy.

[6] Ferrari AC. Raman spectroscopy of graphene and graphite: Disorder, electron-phonon coupling, doping and non-adiabatic effects. Solid State Communications. 2007;**143**:47-57

and Michael Stenbæk Schmidt2

http://dx.doi.org/10.5772/intechopen.74065

217

We acquired SERS spectra for each point of a selected area of pristine graphene films with a high-resolution micro-Raman spectrometer (Horiba Xplora) (see **Figure 11**). The areas were scanned with an acquisition grid of 0.6 and 0.8 μm in x and y, respectively. We selected the wavenumber region 500–1280 cm−1 to represent the functional groups concentration and we constructed the SERS images, illustrated in **Figure 11(b)** and **(d)**, plotting the intensity of the peaks located in this region.

Optical images show significant variation in the dried film thickness along the scanned area, due to a poor dispersibility of pristine graphene in the distilled water. However, the SERS signal is always detectable with good spectral reproducibility and an intensity variation much smaller than that expected, considering that the SERS signal from the second monolayer and beyond is strongly reduced. This finding further confirms that the functional groups are distributed at the edges of graphene structure: the larger thickness and hence the weaker enhancement experienced by the molecular groups, can be compensated by a higher concentration.

**Figure 11.** (a) Image of pristine graphene dried film, acquired with the optical microscope coupled with the Raman spectrometer; the green rectangle indicates the region selected to acquire the map (b). (c) and (d) represent the same for another region of the substrate. The visualization of Raman maps is obtained by using as contrast parameters the intensity of functional group peaks.


3.1.2. Task

The task used in this study was an EEG analogue of the fMRI task used in the pilot. Stimuli in this task consisted of three categories of football defensive formations, with two categories being very visually similar to each other and one category being visually distinct from the other two. For the two similar categories, the subjects needed to discover an explicit counting rule to reliably categorize members of these two groups. For the visually distinct category, subjects could rely on a simple visual similarity analysis to recognize members of this category. Within each category, all of the players were shu ffled around the field of view with the exception of the players on the line of scrimmage, as the number of players on the line dictated category membership (Figure 10). This forced subjects to focus their attention to the line of scrimmage over time while ignoring irrelevant players that are positioned elsewhere on the field.

**Figure 10.** From bottom-left to top right: A fixation cross was shown for 2–3 s. Formations were shown for 2 s while subjects made their response. Immediately following a response, contingent feedback was shown for 1.5 s. Upon feedback termination, a fixation mark was shown for the duration of the inter-trial interval of 2–3 s before the next formation was presented.

Every category had three formations, each sharing the defining number of players on the line of scrimmage for that category, for a total of nine formations used throughout the experiment. On a given trial, the participants were randomly shown one of the nine formations for 2000 ms and they were

instructed to place the stimulus into one of the three categories by pressing a button on a response box within the stimulus exposure window. Once they made a response the stimulus disappeared, and the subject was presented with a corrective feedback screen, which indicated whether they were correct along with text describing the correct category for the stimulus (Figure 10). The feedback was on the screen for 1500 ms, after which a fixation cross with a variable inter-stimulus-interval was shown for 2000–3000 ms. The task was divided into eight training blocks that consisted of 90 trials (or 10 exposures per stimulus) per block, which totaled 80 exposures of every stimulus throughout training.

After the final training block, a generalization block was used, which tested each subject's ability to apply any rules they developed during training to novel stimuli similar to the fMRI pilot. During the training block, a mixture of the nine training stimuli and nine novel stimuli belonging to the same categories were used. The subjects were not told that the generalization block would include novel stimuli. No feedback was given to the participants after pressing a button to categorize each formation. Instead, a black screen was shown for 1500 ms after a response was made before the fixation cross appeared to begin the next trial. Each old and novel stimulus (18 total stimuli) was shown five times for a total of 90 trials in the generalization block.


**Author details**

Miguel Angel Merlos Rodrigo1,2, Naser A. Anjum3 , Zbynek Heger1 , Ondrej Zitka1,2, Adam Vojtech1,2, Eduarda Pereira3 and Rene Kizek1,2\*

\*Address all correspondence to<EMAIL_ADDRESS>
1 Department of Chemistry and Biochemistry, Laboratory of Metallomics and Nanotechnologies, Mendel University in Brno, Brno, Czech Republic

2 Central European Institute of Technology, Brno University of Technology, Brno, Czech Republic

3 CESAM-Centre for Environmental and Marine Studies & Department of Chemistry, University of Aveiro, Aveiro, Portugal


**4. Discussion**

Assuming that the waterworks sludge is virtually inert and does not degrade in the digestion chamber, the entire dry content of the added waterworks sludge will pass through the digestion chamber and be present in the residual biosolids. Based on the information collected from the examined biogas plants included in the study, the waterworks sludge contributes to an increased amount of digestate; that is, about 1–3% based on dry matter, i.e., about 1–3% of TS. The digestate in most plants has a TS content of around 5%, while the waterworks sludge has a TS content of around 15%. The volume increase in the digestate to be handled due to the addition of waterworks sludge is 1% at the most; the TS content in the digestion increases by about 0.1–0.3%, while the total amount of metals in the digestate increases by approximately 1–3% (see calculation in Table 5). Table 5 also refers to the quality requirements according to the biofertilizer certification system, SPCR 120 [12]. This standard states that the proportion of each of the metals (lead, cadmium, copper, chromium, mercury and zinc) may not exceed 15% of the total amount of the metal in the certified biofertilizer. In addition, the nickel content in the biofertilizer from the waterworks sludge must not exceed 6 mg/kg biofertilizer (wet weight). In 2019, around 2.8 million tons of digestate (wet weight) was produced in Sweden, of which 87% was used as fertilizer in agriculture [19]. From farm plants and co-digestion plants, 2.13 million tons, virtually all digestate (biofertilizer), was used as fertilizer. From the wastewater treatment plants, 0.25 million tons (41% of all the sludge) was used as fertilizer certified in the Revaq system. The remaining amount was used mainly as construction material or for the final coverage of landfills [19]. No biosolids are generated at landfill gas plants.

The biogas production from the other plants that also generate biosolids corresponds to a total of 1969 GWh [17]. These plants simultaneously produced 2.8 million tons of biosolids, or around 700 kWh/ton of biofertilizer. Assuming that 1 Nm3 CH4 corresponds to 9.81 kWh [21] and that the biogas contains 65% methane [22], this corresponds to a production of 110 Nm3 of biogas per ton of biofertilizer. According to the values for the 13 plants using waterworks sludge from Ringsjöverket surveyed above, around 1 ton of waterworks sludge is added per 8750 Nm3 of biogas that has been produced. This corresponds to adding 1 ton of waterworks sludge per 108 tons of biofertilizer produced in the plant, excluding the added waterworks sludge, or 9.2 kg of waterworks sludge per ton of biofertilizer produced. Table 5 shows how adding waterworks sludge affects the concentration of metals in the biofertilizer. The starting point for the calculation is the average value of the metal contents in the biofertilizer for the 18 plants that were certified within SPCR 120 in 2014 [23]. Nickel is not included as there is no risk that the content of nickel can reach up to 6 mg/kg wet weight given the concentration of nickel present in the waterworks sludge. Among other heavy metals, lead and chromium make up the largest parts of the total metal concentration, at 7 and 6%, respectively. However, this is below the limit of 15% specified according to SPCR 120. Therefore, this is also not considered to be a problem for the use of waterworks sludge. With the addition of the waterworks sludge, which is assumed to be inert, the S content of the biofertilizer increases. Assuming the same waterworks sludge dose as above, the TS in the biofertilizer increases from 3.9 to 4.0%. An effect of this is that the concentration of metals, stated as mg/kg TS, decreases for, e.g., copper and zinc, while the concentration increases slightly for lead and chromium (see Table 5).

**Table 5.** Average concentration of heavy metals in biofertilizer for the facilities that were certified in 2014 [23] before and after an estimated addition of waterworks sludge. The TS in the biofertilizer is 3.9% before the addition of waterworks sludge. The concentration in the sludge is the average of analyzed data according to Table 3.

Since about half of the waterworks sludge consists of various organic compounds from lake-source water, the waterworks sludge contributes to the increased organic content in soil where the digestate is spread as fertilizer. In many Swedish soils, the organic content is low, which is why this is a welcome contribution to improving the soil's properties. The organic content in soils improves the physical, chemical and biological properties of the soil, such as its water holding capacity, nutrient content, buffer capacity, and the activity of soil organisms.

To reuse material is beneficial for climate and society, and reduces the carbon footprint. According to the evaluation in Sydvatten's Climate Account Report 2020, the production of virgin iron chloride generates about 0.395 kg CO2 emission per kg FeCl3. Since Sydvatten used 3132 tons of FeCl3 in 2020 for drinking water treatment, the reuse of 56% sludge by replacing virgin ferric chloride with waterworks sludge would eliminate 740 tons of carbon dioxide, which is about 17% of all the carbon dioxide that was emitted by the company in 2020 [9], and is well in accordance with EU's Circular Economy Plan [24].


**Jose A. Sanchez 1,\*, Aintzane Conde 2, Ander Arriandiaga 3, Jun Wang 4 and Soraya Plaza 5**

Received: 13 June 2018; Accepted: 26 June 2018; Published: 28 June 2018

**Abstract:** Theoretical models of manufacturing processes provide a valuable insight into physical phenomena but their application to practical industrial situations is sometimes difficult. In the context of Industry 4.0, artificial intelligence techniques can provide efficient solutions to actual manufacturing problems when big data are available. Within the field of artificial intelligence, the use of deep learning is growing exponentially in solving many problems related to information and communication technologies (ICTs) but it still remains scarce or even rare in the field of manufacturing. In this work, deep learning is used to efficiently predict unexpected events in wire electrical discharge machining (WEDM), an advanced machining process largely used for aerospace components. The occurrence of an unexpected event, namely the change of thickness of the machined part, can be effectively predicted by recognizing hidden patterns from process signals. Based on WEDM experiments, different deep learning architectures were tested. By using a combination of a convolutional layer with gated recurrent units, thickness variation in the machined component could be predicted in 97.4% of cases, at least 2 mm in advance, which is extremely fast, acting before the process has degraded. New possibilities of deep learning for high-performance machine tools must be examined in the near future.

**Keywords:** WEDM; deep learning; deep neural networks; Industry 4.0


**1. Introduction**

Water is essential to all life on earth, but its management is facing increasing challenges due to socio-economic pressures such as population growth and the unsustainable use of water resources. Climate change will further exacerbate the water risk for society and the environment, and water-related extremes such as floods and droughts will increase in the future. The long-term aspects of these future trends and the inherent uncertainty within future projections present water managers with considerable challenges. The technocratic approach of working with fixed design standards for engineering seems insu fficient; the environment is constantly changing, and, as a consequence of this, so too are the boundary conditions on which basis engineered water management solutions are developed. Therefore, water management is increasingly developing into an adaptive form of decision making, where flexibility, robustness and resilience are key [1]. Moreover, societal processes and the physical water system are increasingly interwoven, and there are little natural water systems not influenced by human activity. These developments require novel approaches in decision sciences, data processing, modelling techniques, catalyzed by the integration of social and natural sciences [2]. The international journal *Water* addresses these challenges as an outlet for cutting-edge inter-disciplinary approaches in water science. In this Special Issue, topics cover broad aspects of water systems, including water science, water quality, management, and governance.


**3. Rumen environment**

Ruminants are herbivorous mammals considered as latecomers in evolution. Their forestomach is a very complex environment, which allows them to convert plant tissues into nutritious and useful products. The digestive tract of ruminants is formed by various compartments such as reticulum, rumen, omasum, abomasum, small intestine, cecum, colon and rectum [21]. The ruminant stomach is composed by three pregastric fermentation chambers (rumen, reticulum and omasum) [22] (**Figure 1**). Environmental conditions such as temperature (38–42° C), redox potential (250 to 450 mV), pH (5.5–7) controlled by buffer in saliva and osmolarity (260–340 mOsm) [23] provide the ideal conditions for the digestion of plant material by microorganisms. Fibrous components are hydrolyzed and fermented by the interactions among different microbial communities inhabiting the rumen, producing mainly acetate, propionate and butyrate, CO2 , H2 and CH4 . VFAs are the most important source of energy for the animal (75% of the total amount of the digested energy) [24]. Moreover, microbial cell biomass is the major source of protein and amino acids [25]. Microbial population also synthetizes vitamins B and K and employs detoxification mechanisms for phytotoxins and mycotoxins [26].

Microbial ruminant ecosystem is composed by a high microbial population density, predominantly obligate anaerobic microorganisms. Bacteria are the most abundant microorganisms and more than 50% of the cell mass in the rumen are comprised of at least 50 bacterial genera (1010 –1011 ml-1), followed by 25 genera of ciliate protozoa (104 –106 ml-1), six genera of fungi (103 –106 ml1 ), methanogenic archaea (107–1010 ml1 ) and bacteriophages (108–109 ml1 ) [27–29], nevertheless only 10% of these microbiome have been identified and described [30]. Livestock Methane Emission: Microbial Ecology and Mitigation Strategies http://dx.doi.org/10.5772/65859 55

Emissions by manure management, mostly CH4

[13]. They have reported that CH4

29%, respectively, from 2000 to 2020.

emission from manure was 62.24 Gg CH4

N2

54 Livestock Science

of CH4

N2

ture (38–42°

and mycotoxins [26].

–106 ml1

fungi (103

and N2

29.49 and 2.42 Gg CH4

O due to manure [14].

**3. Rumen environment**

acetate, propionate and butyrate, CO2

and N2

O was 53 and 47%, respectively, while FAO [3] estimated global GHG emis-

, respectively [16]. Similarly, FAO [3] reported that Asia, Central and

decomposition carried out by anaerobic microbial activities. These emissions depend on specific manure composition and quantity produced which, in turn is dependent on other factors

enteric fermentation are higher than those from manure [13, 16], manures also contribute to

Asia, particularly China, Western Europe and North America are the regions with the highest GHG emissions from manure management [14]. According to EPA [20], global GHG

South America, Sub-Saharan Africa, Western Europe, North America, Eastern Europe and the Commonwealth of Independent States were the regions with the highest emissions of

Ruminants are herbivorous mammals considered as latecomers in evolution. Their forestomach is a very complex environment, which allows them to convert plant tissues into nutritious and useful products. The digestive tract of ruminants is formed by various compartments such as reticulum, rumen, omasum, abomasum, small intestine, cecum, colon and rectum [21]. The ruminant stomach is composed by three pregastric fermentation chambers (rumen, reticulum and omasum) [22] (**Figure 1**). Environmental conditions such as tempera-

osmolarity (260–340 mOsm) [23] provide the ideal conditions for the digestion of plant material by microorganisms. Fibrous components are hydrolyzed and fermented by the interactions among different microbial communities inhabiting the rumen, producing mainly

and CH4

energy for the animal (75% of the total amount of the digested energy) [24]. Moreover, microbial cell biomass is the major source of protein and amino acids [25]. Microbial population also synthetizes vitamins B and K and employs detoxification mechanisms for phytotoxins

Microbial ruminant ecosystem is composed by a high microbial population density, predominantly obligate anaerobic microorganisms. Bacteria are the most abundant microorganisms and more than 50% of the cell mass in the rumen are comprised of at least 50 bacterial

[27–29], nevertheless only 10% of these microbiome have been identified and described [30].

, H2

genera (1010 –1011 ml-1), followed by 25 genera of ciliate protozoa (104

), methanogenic archaea (107–1010 ml1

C), redox potential (250 to 450 mV), pH (5.5–7) controlled by buffer in saliva and

O emissions due to volatile nitrogen losses, principally in form of ammonia (NH3

as animal type, breed, weight, diet and climate conditions. Although CH4

and N2

emissions from manure management were 446 million tonnes of CO2

sions from manure management were 368 million tonnes of CO2

O, are produced during the manure

O emissions from manure would increase by 20 and

, where beef cattle and dairy cow emitted with

. VFAs are the most important source of

–106

) and bacteriophages (108–109 ml1

ml-1), six genera of

)

emissions from

) and NOx

**Figure 1.** Ruminant digestion process. Note: Gastrointestinal tract of ruminants and main biochemical processes occurr ing in it.

The interactions of these microorganisms are widely different, namely mutualism, commensalism, syntrophy, competition and depredation [31, 32].

Hydrolysis of plant polysaccharide material is the first step in the enteric fermentation process, and 80% of plant cell material degradation is carried out by bacteria and fungi, and the rest 20% is by protozoa [33]. In the second stage, monomers are fermented to VFAs, branched chain VFAs, organic acids (lactate), alcohols, CO2 and H2 . VFAs are absorbed by the rumen and omasal walls of the host animal for its nutrition [10]. Though several parameters such as rumen fluid, volume, pH and VFAs, concentration can disturb this absorption [34]. Free acids can be oxidized by obligate hydrogen producing bacteria to acetate, albeit this reaction is thermodynamically non-favorable, and hence are carried out only in synthropic association with hydrogen consuming bacteria or archaea, which diminish the partial pressure of H2 . When the conditions are not favorable, VFAs are accumulated, decreasing the pH and inhibiting rumen microbiome [35, 36]. NH3 is produced due to proteolysis and can be used by microorganisms to build their own proteins. The excess of NH3 is absorbed by the rumen wall and transported by the animal blood [37]. The digested proteins, lipids and the carbohydrate constituents of microbial cells are exploited in the small intestine for the maintenance of the animal and the production of meat and milk. During enteric fermentation, a large quantity of CO2 is produced due to diverse biochemical processes. A part of this CO2 produced is released through eructation or normal respiration, and other part is reduced with H2 to CH4 by hydrogenotrophic methanogens. Methane produced is primarily released through eructation and approximately 10–15% is emitted by normal respiration and via flatus [10]. CH4 production can be accomplished by the reduction of acetate and methyl-containing C1 compounds, nonetheless these pathways are not common in the rumen [38]. About 2–12% of gross energy intake (GEI) produced in the rumen by fermentation is converted to methane, which apart from leading to the loss of the feed energy, results in the emission and consequently, global warming [39].


>V0:=1:

one of the data transmitting routers. The PD measurements will lead to a lot of raw data and normally they can't be sent directly to the remote controlling center due to its high data volume. After processing, the data can be sent back to the controlling and data concentrator for

Because the shielded power cables are widely used in modern HV power systems and the fact that the partial discharge is a powerful tool for assessing the HV power system status, HF PD electromagnetic wave propagation, detection, and analysis have been extensively studied. In this chapter, the authors look into the details of the shield power cable structure, their HF attenuation properties, PD electromagnetic wave propagation, and address the detection and

**Appendix: Maple program for loss calculations in a typical jacketed**

analysis of the HF electromagnetic wave in the shielded power cable.

>epsilon:=2.2:#Epsilon is the dielectric constant of the insulation.

appropriate actions such as cable maintenance, alarm generation, etc.

**Figure 16.** One Zigbee node.

110 Advanced Electromagnetic Waves

**shielded cable**

>epsilon0:=8.85e-12: >mu1:=1\*4\*Pi\*1e-7:

>restart;

**4. Summary and discussion**

>Rc:=4e-3:# Rc is the conductor radius.

>Rs:=11.7e-3: #Rs is the ground shield radius (m).

>Rd:=11.2E-3:#Rd is the insulation radius (m).

>N:=4:# N is the number of neutral wires.

>omega:=2\*Pi\*f:

>epsilon0:=8.85e-12:

>l:=1:# let the length of the cable be 1 m;

>T:=0.5e-3:# T is the thickness of the ground shield.

>T2:=0.2-3:# T2 is the thickness of the conductor shield.

>d:=evalf(2\*Pi\*Rs/N):# d is the length between two neutral wires.

>C:=2\*Pi\*epsilon\*epsilon0\*l/(ln(Rs/Rc)):# Capacitance of the insulation per meter.

>C1:=2\*Pi\*epsilon\*epsilon0/(ln(Rd/Rc)):

>L1:=mu1\*ln(Rs/Rc)/(2\*Pi):

>Zc:=evalf(sqrt(L1/C1)):#Characteristic impedance.

```
>K1:=1/((sigma3+omega*epsilon0*epsilon3*I)*l*T):
```
>K2:=-2\*I/omega/C/1\*Pi\*Rs+T2/(sigma4+omega\*epsilon4\*epsilon0\*I)/1:

>I1:=

2)/K2^(1/2)/(1+exp(1/K2^(1/2)\*K1^(1/2)\*d)):#

Current distribution along the ground shield.

>V1:=-V0\*(exp(1/K2^(1/2)\*K1^(1/2)\*x)+exp(-K1^(1/2)\*(-d+x)/K2^(1/2)))/K2^(

```
1/2)/(1+exp(1/K2^(1/2)*K1^(1/2)*d)):#
```
90

Voltage distribution along the ground shield.

>I2:=(-V1)/K2:# Current flowing through the conductor shield.

>dZr4:=T2/(sigma4\*l\*dx):# dZr4 is the elemental resistive impedance of the conductor shield.

>dZc4:=1/(I\*omega\*(epsilon0\*epsilon4\*l\*dx/T2)):# dZc4 is the elemental capacitive impedance of the conductor shield.

>Ratio2:=simplify(dZc4/(dZc4+dZr4)):# To get the current flowing through the resistive component of the conductor shield, we calculate Ratio2.

>Irtotal2:=I2\*Ratio2:# Irtotal2 is the current flowing through resistive component

of the conductor shield.

>dZr3:=(1\*dx)/(sigma3\*l\*T):# Same as above.

```
>dZc3:=1/(I*omega*(epsilon0*epsilon3*l*T/dx)):# Same as above.
>Ratio1:=simplify(dZc3/(dZc3+dZr3)):# Same as above.
>Irtotal:=I1*Ratio1:# Irtotal1 is the current flowing through resistive component
of the ground shield.
>Ii:=Im(Irtotal):
>Ir:=Re(Irtotal):
>Ii2:=Im(Irtotal2):
>Ir2:=Re(Irtotal2):
>Pd4:=int(((Ir2)^2+(Ii2)^2)*(T2/(sigma4)),x=0..d/2):# Conductor shield power
dissipation
>Pd3:=int(((Ir)^2+(Ii)^2)*(1/(sigma3*T)),x=0..d/2):# Ground shield power dissipation
>Pin:=(V0)^2/Zc:# Input power.
>dB3:=10*log10(1-(Pd3*2*N/Pin)):# Ground shield attenuation.
>dB4:=10*log10(1-(Pd4*2*N/Pin)):# Conductor shield attenuation.
```