area and the faster the rate of adsorption kinetics. in vapour phase systems this needs to be considered against pressure drop, which will affect energy cost. careful consideration of particle size distribution can provide significant operating benefits. however, in the case of using activated carbon for adsorption of minerals such as gold, the particle size should be in the range of 3.35–1.4 millimetres (0.132–0.055 in). activated carbon with particle size less than 1 mm would not be suitable for elution (the stripping of mineral from an activated carbon). modification of properties and reactivity acid-base, oxidation-reduction and specific adsorption characteristics are strongly dependent on the composition of the surface functional groups. the surface of conventional activated carbon is reactive, capable of oxidation by atmospheric oxygen and oxygen plasma steam, and also carbon dioxide and ozone. oxidation in the liquid phase is caused by a wide range of reagents (hno3, h2o2, kmno4). through the formation of a large number of basic and acidic groups on the surface of oxidized carbon to sorption and other properties can differ significantly from the unmodified forms. activated carbon can be nitrogenated by natural products or polymers or processing of carbon with nitrogenating reagents. activated carbon can interact with chlorine, bromine and fluorine. surface of activated carbon, like other carbon materials can be fluoralkylated by treatment with (per)fluoropolyether peroxide in a liquid phase, or with wide range of fluoroorganic substances by cvd-method. such materials combine high hydrophobicity and chemical stability with electrical and thermal conductivity and can be used as electrode material for super capacitors. sulfonic acid functional groups can be attached to activated carbon to give "starbons" which can be used to selectively catalyse the esterification of fatty acids. formation of such activated carbons from halogenated precursors gives a more effective catalyst which is thought to be a result of remaining halogens improving stability. it is reported about synthesis of activated carbon with chemically grafted superacid sites –cf2so3h. some of the chemical properties of activated carbon have been attributed to presence of the surface active carbon double bond. the polyani adsorption theory is a popular method for analyzing adsorption of various organic substances to their surface. examples of adsorption heterogeneous catalysis the most commonly encountered form of chemisorption in industry, occurs when a solid catalyst interacts with a gaseous feedstock, the reactant/s. the adsorption of reactant/s to the catalyst surface creates a chemical bond, altering the electron density around the reactant molecule and allowing it to undergo reactions that would not normally be available to it. reactivation and regeneration world's largest reactivation plant located in feluy, belgium. activated carbon reactivation center in roeselare, belgium. the reactivation or the regeneration of activated carbons involves restoring the adsorptive capacity of saturated activated carbon by desorbing adsorbed contaminants on the activated carbon surface. thermal reactivation the most common regeneration technique employed in industrial processes is thermal reactivation. the thermal regeneration process generally follows three steps: adsorbent drying at approximately 105 °c (221 °f) high temperature desorption and decomposition (500–900 °c (932–1,652 °f)) under an inert atmosphere residual organic gasification by a non-oxidising gas (steam or carbon dioxide) at elevated temperatures (800 °c (1,470 °f)) the heat treatment stage utilises the exothermic nature of adsorption and results in desorption, partial cracking and polymerization of the adsorbed organics. the final step aims to remove charred organic residue formed in the porous structure in the previous stage and re-expose the porous carbon structure regenerating its original surface characteristics. after treatment the adsorption column can be reused. per adsorption-thermal regeneration cycle between 5–15 wt% of the carbon bed is burnt off resulting in a loss of adsorptive capacity. thermal regeneration is a high energy process due to the high required temperatures making it both an energetically and commercially expensive process. plants that rely on thermal regeneration of activated carbon have to be of a certain size before it is economically viable to have regeneration facilities onsite. as a result, it is common for smaller waste treatment sites to ship their activated carbon cores to specialised facilities for regeneration. other regeneration techniques current concerns with the high energy/cost nature of thermal regeneration of activated carbon has encouraged research into alternative regeneration methods to reduce the environmental impact of such processes. though several of the regeneration techniques cited have remained areas of purely academic research, some alternatives to thermal regeneration systems have been employed in industry. current alternative regeneration methods are: tsa (thermal swing adsorption) and/or psa (pressure swing adsorption) processes: through convection (heat transfer) using steam, "hot" inert gas (typically heated nitrogen (150–250 °c (302–482 °f))), or vacuum (combining tsa and psa processes) in situ regeneration mwr (microwave regeneration) chemical and solvent regeneration microbial regeneration electrochemical regeneration ultrasonic regeneration wet air oxidation