Use of packed scrap iron anodes for continuous electrochemical Cr(VI) reduction process in electroplating wastewater treatment

The performance of an electrochemical reduction process was investigated for the treatment Cr(VI)-containing electroplating wastewater using a continuous-flow scrap iron packed column as an sacrificial anode. The effects of the key operating parameters including hydraulic retention time (HRT), current supply ratio (CSR), and inlet Cr(VI) concentration were systematically studied. With a fixed CSR of 106%, the HRT has no impact on Cr (VI) removal, but energy consumption increased with decreasing HRT. A complete Cr(VI) removal was obtained with a final ORP of approximately -100 mV. Increasing the inlet Cr(VI) concentration caused an inefficient removal efficiency of Cr(VI) with an increases in ORP. In contrast, Cr(VI) removal remained virtually unchanged, but ORP was dramatically decreased, when the influent Cr(VI) concentration decreased. Continuous and complete Cr(VI) reduction via electrochemical reactions can be achieved by the ORP range of -200 to -100 mV. The operating cost using continuous flow treatments with HRT of 60 min required less than batch reactor treatment around 40-57%.