Simultaneous removal of nitrate, copper and hexavalent chromium from water by aluminum-iron alloy particles

Groundwater contamination is a worldwide concern and the development of new materials for groundwater remediation has been of great interest. This study investigated removal kinetics and mechanisms of nitrate, copper ion and hexavalent chromium (20-50 mg L^-1) by particles of Al-Fe alloy consisting of 20% Fe in batch reactors from a single KNO₃, CuSO₄, Cu(NO₃)₂, K₂Cr₂O₇ and their mixed solutions. The effects of contaminant interactions and initial pH of the solution were examined and the alloy particles before and after reaction were characterized by X-ray diffraction spectrometer, scanning electron microscopy and X-ray photoelectron spectroscopy. The removal mechanisms were attributed to chemical reduction [Cu(II) to Cu, NO₃^- to NH₃ and Cr(VI) to Cr(III)] and co-precipitation of Cr(III)-Al(III)-Fe(III) hydroxides/oxyhydroxides. Cu(II) enhanced the rates of NO₃^- and Cr(VI) reduction and Cr(VI) was an inhibitor for Cu(II) and NO₃^- reduction. This study demonstrates that Al-Fe alloy is of potential for groundwater remediation.