Mitigation of Chromium Contamination by Copper-ZVI Bimetallic Particles

Soil and water pollution by chromium is a major environmental concern. Although existence of chromium in the ${\mathrm{Cr}}^{3+}$ state is considered benign, its presence in the ${\mathrm{Cr}}^{6+}$ state poses an environmental concern. Hence, reduction of chromium(VI) to chromium(III) is considered as a satisfactory environmental solution to mitigate chromium contamination. The oxidation of a metal substrate can be enhanced by depositing a small amount of nobler metal on its surface. The present study thus examines the efficiency of chromium(VI) reduction upon deposition of copper (oxidation potential: $-0.34\mathrm{V}$) on the surface of zero-valent iron (ZVI) (oxidation potential: 0.04 V) particles. Batch experiments and pH and Eh measurements revealed that presence of copper loading on ZVI particles increases the efficiency of chromium(VI) reduction by 11–233% in relation to the uncoated ZVI particles owing to enhanced electron activity and release of hydroxyl ions that converted chromium(VI) to mixed Fe–Cr oxide. The chromium(VI) reduction was accomplished in periods ranging from 60 to 240 min in the batch experiments and obeyed the pseudo first- or second-order kinetics.