Electrolytic Manganese Residue Detoxification

Electrolytic Manganese residue(EMR)is generated by acid leaching,descaling,neutralization and filtration during the production of electrolytic metal manganese from manganese ore.At present,China's storage of EMR is more than 160 million tons.EMR contains high contents of migratable manganese ions and ammonia nitrogen.During stacking,these manganese ions and ammonia nitrogen would enter the surface water and groundwater with rains or as leachates,contaminating the surrounding environment.Therefore,harmless and resource-based treatment of EMR is an urgent issue in electrolytic manganese industry.In this study,first,the harmless treatment and reutilization of EMR was reviewed.Then The basic physicochemical properties of EMR were examined by X-ray diffraction,scanning electron microscopy,X-ray fluorescence,and Brunauer Emmett Teller.Finally,manganese and ammonia nitrogen were removed from EMR by electric field enhanced leaching.The results show that EMR harmless is more urgent than its resource utilization.EMR detoxification is up to manganese and ammonia nitrogen.EMR mainly consists of Si O2,SO3,Ca O,Fe2O3,Mn O and Al2O3.(NH4)2Mn(SO4)2·6H2O and(NH4)2 Mn(SO4)2 in EMR are formed by the reaction of manganese sulfate and ammonium sulfate.The concentrations of Zn,Cd,Pb,Ni and As in EMR leachate are respectively 300.76 mg/kg,10.50 mg/kg,85.84 mg/kg,528.66 mg/kg,39.27 mg/kg,all of which exceed the threshold of GB 15618-2018.The leaching efficiencies of manganese and ammonia nitrogen efficiency were 91.2% and 92.0%,respectively.Under the optimum leaching condition of HCl dosage(9%),current density(30 m A/cm2),leaching time(120 min),leaching temperature(20 ?),solid to liquid ratio(1:5),the leaching efficiency of manganese and ammonia nitrogen is up to 91.2% and 92.0% respectively.All metals except Cd and Ni in the leachate of EMR after leaching are below the national standards of “soil environment quality risk control standard for soil contamination of development land”(GB 15618—2018).This means that electric field could enhanced the leaching of manganese and ammonia nitrogen as well as other heavy metals since the electric field could change the surface charge distribution of EMR particles,providing another approach for EMR detoxification.