Retention of toxic pollutants by nanomagnetite aggregates
Iron (hydr)oxides are widely considered as important factors for the immobilisation of many contaminants, while their nano-scale counterparts offer greater retention capacity. Successful immobilisation of contaminants is documented, for instance, via nanomagnetite, although this solid is far less studied compared to other Fe oxides. Soil aggregates are natural systems ideal for the study of the (bio)geochemical reactions that control the mobility of the redox sensitive elements due to their small size and their spatial heterogeneity. The reduction of contaminants by Fe (hydr)oxides using artificial aggregate systems has been studied via experimental set ups that mimic the field conditions, showing the great retention potential of important toxic pollutants. These systems have been originally developed in a macro-scale via flow-through reactors using constructed aggregates coated with ferryhydrite and indicated the successful retention of Se and As. Thus, the purpose of the present study is to use those systems in a micro-scale edition via the use of microfluidics and PEG aggregates in order to study the nanomagnetite immobilisation potential of various contaminated systems (i.e. Se, As, Cr, Sb, U). We aim to obtain Break Through Curves (BTC) of the contaminants of interest to investigate the spatial distribution of the phases produced by nanomagnetite reduction and to assess all the driving geochemical and physical processes. Micro X-Ray Tomography (SR-CT) and µXAS will be applied for the first time to such experimental systems, offering a 3D description of the various species present in these aggregates. A numerical (3D) reactive transport model will be, also, used to interpretate the time-resolved data obtained in such a natural system and to set up new water treatments based on such macroscopic devices. We aim to provide innovative insights and set the basis for alternative remediation techniques with respect to drinking and waste water contamination worldwide.