Simultaneous removal of trichloroethylene and hexavalent chromium by green synthesized agarose-Fe nanoparticles hydrogel

Abstract

The development of highly efficient, eco-friendly and cost-effective remediation technology to remove mixed contaminants is now in progress. Here, agarose-Fe nanoparticles (NPs) hydrogel were produced via two green steps to remove mixed contaminants, specifically trichloroethylene (TCE) and hexavalent chromium (Cr(VI)). Approx. 84.9% of Cr(VI) and 93.8% of TCE were simultaneously removed over 24h in their co-existing solution, while 94.1% of Cr(VI) and 97.2% of TCE were separately removed by agarose-Fe NPs hydrogel. Scanning Electron Microscopy (SEM) suggested that the macroporosity of agarose-Fe NPs hydrogel facilitated the mass transfer between agarose-Fe NPs hydrogels and mixed contaminants, and that Fe NPs were uniformly immobilized into the hydrogel. X-ray Photoelectron Spectroscopy (XPS) and Fourier Transform Infrared Spectroscopy (FTIR) provided evidence supporting the co-removal mechanism. XPS result indicated that: (1) chemical reduction played a role in the removal of both Cr(VI) and TCE; and (2) iron oxides and Fe(III)–Cr(III) complexes might be formed after reaction. FTIR result showed that some functional groups were involved in the removal process. Moreover, the presence of iron oxides were confirmed by FTIR. Both SEM and XPS results verified that encapsulation could describe such immobilization of Fe NPs using agarose. Finally, the kinetics study supported the removal mechanism. Such encapsulation of Fe NPs via a green strategy is simple, quick, and cost-effective, making in situ remediation of mixed contaminants more favorable.