Synergistic harmless treatment of phosphogypsum leachate wastewater with iron-rich electrolytic manganese residue and electric field

Abstract

In the iron-rich electrolytic manganese residue (IREMR) and phosphogypsum leachate wastewater (PLW), there are high levels of Mn2+, NH4+-N, F−, and PO43− pollutants which severely contaminate the surrounding environment. This study focuses on a synergistic and environmentally friendly treatment of PLW using IREMR and an electric field. During the mixed leaching process, with a mass ratio of IREMR to PLW of 1:25, a reaction temperature of 25 °C, a leaching pH of 3.0, and a reaction time of 30 min, the concentrations of Mn2+ PO43−, NH4+-N, and F− in the mixed leaching wastewater were measured to be 1235.49 mg/L, 1507.97 mg/L, 700.15 mg/L, and 146.76 mg/L, respectively. In the pollutant precipitation removal process, with a pH of 9.5 in the mixed leaching wastewater, a current density of 10 mA/cm2, a reaction temperature of 35 °C, and a reaction time of 45 min, the removal efficiencies of Mn2+, PO43−, NH4+-N, and F− were found to be 99.81 %, 99.86 %, 58.37 %, and 99.90 %, respectively. The removal mechanism indicates that Mn2+, F−, PO43−, and NH4+-N were primarily eliminated through the formation of Mn(OH)2, Mn3(PO4)2·2H2O, CaF2, MnF2, and Mg(NH4)PO4·6H2O. This research offers a new approach for the resource utilization and environmentally safe treatment of PLW.