Study On Crystal Shape Control Rule Of MnO₂ And Discharge Performance For Electrolytic Manganese Anode Slime

Electrolytic manganese anode slime?EMAS? is a kind of solid waste produced in the anode chamber during electrolytic manganese metal production. It contained manganese and other valuable elements. With the rapid development of electrolytic metal manganese, the problem of harmless treatment and resource utilization about EMAS is increasingly emergent. According to the current smelting technology, to produc one ton of electrolytic metal manganese, it will generate 50-150 kg of manganese anode slime. Because of the economic and technical reasons, the enterprise's treatment about EMAS still is except a few as additives used in steel making, and the vast majority is dumped as hazardous waste or sold for small value. Therefore, the recycling use of electrolytic manganese anode slime research can not only reduce the pollution of the environment, but also promote the development of the electrolytic manganese industry.In the work, the EMAS was from an electrolytic manganese factory in Xiushan of Chongqing. For the sake of knowing EMAS, a variety of physical and chemical analysis methods were firstly used to analyze its basic properties. Then studied the effect of crystal morphology, pore size distribution, chemical composition etc on the discharge performance by calcining at the high temperature for controlling crystal shape of MnO₂ and pickling for purification. The experimental conclusions were as follows:EMAS was a substance with small particles, black and mud paste powder. And the main constituents of EMAS were Mn, Pb, Se, Fe, Mg, S and other elements, the percentage content were as follows: total manganese?46.76 wt %?, lead?6.55 wt %?, selenium?0.28 wt %?.In the process of controlling crystal shape of MnO₂ to improve the performance of EMAS's discharge, the choice of calcining temperature and calcining time was discussed. It was proved that the optimal temperature was 400 ? for the crystal shape controlling of MnO₂, and the corresponding experimental conditions were confirmed. In the study of exploring the effection on improving discharge performance with pickling, the experimental conditions such as the liquid solid ratio, pickling temperature, sulfuric acid concentration and pickling time were disscussed. And the experimental results indicated that reaction conditions in controlling crystal structure regulation of MnO₂ and acid pickling were that: it was calcined for 1 h at 400 ?, then pickled for 0.5 h with 1 mol·L-1 sulfuric acid solution at 25 ??room temperature?, liquid-solid ratio of 8, EMAS had evenly distuibuted sizes, crystal morphology, significantly decreased gap through controling crystal shape and pickling to removing impurities in electrolytic manganese anode slime. And specific surface area increased from 33.11 m2·g-1 to 93.53 m2·g-1, micropore volume increased from 0.0129 cm3·g-1 to 0.0362 cm3·g-1. The active EMAS's specific capacity reached up to 249.65 mAh·g-1 after assembing simulation of alkaline manganese battery.In the research, the phase composition, pore size distribution, chemical composition and surface morphology were analyzed by means of XRD, BET, XRF and SEM analysis method. It was determined: ?-MnO₂??-MnO₂ were changed into ?-MnO₂ in EMAS after crystal structure controlling of MnO₂ and pickling. The presence of ?-MnO₂ would improve discharge performance as alkaline manganese battery cathode material. At the same time, the non-conductive oxides and parts of the cation were dissolved by using of sulfuric acid solution for EMAS, which was possible to achieve harmless treatment and resource utilization for EMAS.