Simultaneous Reduction of Vanadium (V) and Chromium (VI) in Wastewater by Nanosized ZnWO<SUB>4</SUB> Photocatalysis

Vanadium (V, V) and chromium (Cr, VI) are simultaneously photocatalytically reduced to less-toxic V(VI) and Cr(III) by mimetic solar light with ZnWO4 nanoparticles prepared by hydrothermal synthesis. The reduction efficiencies can reach 68.8% for V(V) and 97.3% for Cr(VI) in 3 h, respectively, which are comparable to those by microbial fuel cell technology carried out in over 10 days. The prepared ZnWO4 nanoparticles are characterized by XRD, SEM, EDS, TEM, and Uv-vis-DRS tests. Electrochemical calculation shows high acidity benefits the rapid reduction of V(V) and Cr(VI). In addition, the applied ZnWO4 nanoparticles can be recycled and reused for 5 repeated photocatalytic reduction runs. And after 5 runs, the recycled ZnWO4 nanoparticles can also present good photocatalytic activity with a reduction efficiency of about 60% for V(V) and 90% for Cr(VI). The new procedure on the simultaneous reduction of V(V) and Cr(VI) by photocatalysis may be promisingly applied in contaminated wastewaters, combining the remediation and possible V and Cr recovery.