Elec-accumulating behaviors of manganese in the electrokinetics-processed electrolytic manganese residue with carbon dioxide and oxalic acid

An electrokinetic treatment for the accumulation of manganese in electrolytic manganese residue (EMR) was investigated. Electrokinetic experiments were conducted in a self-made electrokinetic device with CO2 bubbled into the cathode region as well as deionized water (EKCa), Na2SO4 (EKCb), Na2C2O4 (EKCc) and H2C2O4 (EKCd) pretreating the EMR, respectively. The potential difference, the pH, the accumulated content of manganese, the manganese fractionation and the energy consumption were investigated during the electrokinetic experiments. The results revealed that the accumulated content of manganese at the cathode region during the electrokinetic experiments with CO2 and different pretreating reagents was higher than that during the direct electrokinetic experiment. The manganese content of the cathode region increased gradually with an increasing electrokinetic time during EKCa, EKCb, EKCc and EKCd. The total manganese content and the combinative exchangeable and carbonate content at the cathode region had the maximum 7.5% and 6.3%, respectively, during EKCd, and the energy consumption per gram accumulated manganese of EKCd was lowest. These patterns were because CO2 reacted with OH- ions generated at the cathode region to produce CO32- ions and reduced the resistance, and CaMn2O4 from the EMR was reduced to Mn2+ ions by H2C2O4 in acidic regions. (C) 2020 Elsevier B.V. All rights reserved.