Preparation Of Lead Oxide And Active Manganese Dioxide From Electrolytic Manganese Anode Slag

Electrolytic manganese anode slag is a dark brown by-product produced by anodic oxidation of Mn²⁺in the production of electrolytic metal manganese.Its main components are manganese dioxide and lead.In the electrolytic manganese process,a lead alloy plate is generally used as the anode.During the electrolysis process,the lead on the anode plate will fall off and be doped in the anode slag.Therefore,there is a large amount of lead in the slag,which is a highly toxic hazardous waste.Anode slag is difficult to handle,so it is generally used as hazardous solid waste storage,steelmaking additives,or sold at low prices,failed to get good development and utilization.At present,there is no mature method to recover manganese anode slag.In this paper,electrolytic manganese anode slag from a factory in Xiang Xi Hunan is used as the raw material to recover lead and prepare manganese dioxide.The main components of the pre-processing anode slag are manganese dioxide and lead,the content of lead is12.4%,manganese is 53.2%,the main phase is Mn O₂Pb _XMn O₂,the crystallization of anode slag is not high,lead is doped in the lattice of manganese dioxide in the form of Pbx Mn O₂,and its surface structure is dense.The main crystalline structure of manganese anode slag after 800 ^oC calcination for 2hours is that the Mn₂O₃and Pb O,surfaces become loose and porous,which provides the basis for the leaching of lead ions.The leaching recovery of lead in calcined anode slag was carried out with ammonium acetate solution.The experimental results showed that the leaching rate of lead was the highest when the concentration of ammonium acetate was 4 mol/L,temperature 85^oC,the average particle size of anode slag was 18?m,the leaching time was 40 min,liquid-solid ratio 7:1.Under this condition,the leaching rate of lead is91.23%.The precipitation rate of lead carbonate is 98.29%,the purity of lead oxide is 93.48%,and the recovery rate of total lead is 89.66%.The lead in anode slag was leached by hydrochloric acid-ammonium chloride and hydrochloric acid-sodium chloride system,respectively.The experimental results show that the best leaching conditions of hydrochloric acid-ammonium chloride system are:hydrochloric acid concentration 1.2%,ammonium chloride concentration5.5 mol/L,time 40 min,temperature 50 ^oC,liquid-solid ratio 8:1,anodic slag particle size 18?m,lead leaching rate 91.23%,leaching slag lead grade 1.21%.The optimum leaching conditions of hydrochloric acid-sodium chloride are:hydrochloric acid concentration 1.4%,sodium chloride concentration 5 mol/L,time 40 min,temperature 70 ^oC,stirring rate 200 rap/min,liquid-solid ratio 8:1,lead leaching rate92.84%,at this time the lead content in the leaching slag is 0.986%.In contrast,the lead leaching rate of hydrochloric acid-sodium chloride system is slightly higher.The leaching residue of hydrochloric acid-sodium chloride system was analyzed by XRD,mainly Mn₂O₃.adding sodium carbonate to recover lead,the precipitation rate of lead reached 99.70%,and the recovery rate of total lead was 92.32%.The leaching rate of lead in three systems is ideal,compared with that of hydrochloric acid-sodium chloride system,which is cheap and less corrosive.the anodic mud after leaching from hydrochloric acid-sodium chloride system was disproportionated.the experimental results showed that the optimum technological conditions for Mn?III?dissolution were:temperature 65 ^oC,sulfuric acid volume concentration 15%,time 3 hours,liquid-solid ratio 3:1,dissolution rate 99.88%.the chemical manganese dioxide was prepared by adding sodium chlorate after disproportionation,and its vibrational density was 1.1 g/cm³,manganese dioxide was mainly?-Mn O₂ crystalline,Purity 93.2%and the particle size distribution range was between 1052?1700 nm and its surface area is 81 g/cm².