Adsorption and reduction of hexavalent chromium on magnetic greigite (Fe3S4)-CTAB: leading role of Fe(ii) and S(-ii)

In this study, a facile one-step route was used to synthesize a novel magnetic mesoporous greigite (Fe3S4)-CTAB composite, which was utilized to remove hexavalent chromium (Cr(vi)). The optimized Fe3S4-CTAB(0.75) composite with a CTAB dosage of 0.75 g possessed the maximum specific surface, showing the highest Cr(vi) adsorption capacity of 330.03 mg g(-1). The mechanism analysis revealed that Fe(ii) and S(-ii) were critical for the reduction of Cr(vi). CTAB can promote the removal of Cr(vi) by Fe3S4-CTAB composites, possibly due to increased S(-ii) concentration, better dispersion of nanoparticles, and greater zeta potential. Besides, there is mild effect of Fe-0 on Cr(vi) removal, which is confirmed by the disappearance of the Fe-0 peak from the XPS analysis. The pseudo-second-order kinetic model could explain the Cr(vi) removal processes well. The adsorption of Cr(vi) at different initial concentrations was more consistent with a Langmuir isotherm. The existence of H+ was beneficial for Cr(vi) removal by Fe3S4-CTAB(0.75). Our work confirmed that the obtained Fe3S4-CTAB(0.75) composites exhibit considerable potential for Cr(vi) removal from aqueous solution.