Hydrometallurgy Of Pyrolusite Intensified By Electric Field

With the rapid development of steel industry since twenty-first century,the demand of manganese metal as an important additive of steel industry had been rising rapidly,resulting in the fast consumption of a large number of high-quality manganese carbonate resources.Therefore,the comprehensive utilization of pyrolusite resources had been paid more and more attention.Based on the basic principles of chemical process intensification,the basic theories of leaching kinetics,the analysis methods of thermodynamics and electrochemical,this paper took the pyrolusite provided by an electrolytic manganese enterprise in Guangxi as the research object,and carried out the following works around the leaching and electrolysis process of pyrolusite.?1?Experimental study on hydrometallurgical leaching and electrolysis of pyrolusite and pyrite intensified by electric field.The results showed that the reduction leaching process of pyrolusite was strengthened by electric field.The extraction of pyrolusite was increased by 10%to 20%than that without electric field under the same conditions.In addition,the amount of pyrite was decreased by 40%;the leaching time was shortened by 60 min;the usage of sulfuric acid was reduced by 40%.According to the dynamic analysis of leaching process,it was shown that the leaching process of pyrolusite intensified by electric field was controlled by surface chemical reaction.The apparent activation energy was calculated to 53.76 kJ·mol^-1,and the dynamic equation could be expressed as:1-?1-X?^1/3=3.53×10⁵?[FeS₂/MnO₂]^0.264?[H₂SO₄]^0.571?[j]^1.194?exp??53.76×10³/RT??t.The leaching process of pyrolusite under without electric field was controlled by the diffusion of product,and the apparent activation energy was 80.11kJ·mol^-1.This indicated that the introduction of electric field could effectively decrease the apparent activation energy of the leaching reaction,reduce the adsorption of elemental sulfur on mineral particles and increase the collision frequency between mineral molecules,thereby dredging the electron channel of Fe?II?/Fe?III?to promote the leaching rate of pyrolusite.The electrolysis process of the two ore electrolyte prepared under the electric field was normal.It was indicated that the electric field could eliminate the adverse effects of sulfur-containing compounds at low valence on the electrolytic manganese metal to a certain extent.?2?Study on the mechanism study of sulfur-containing compounds formation and the influences of sulfur-containing compounds at low valence on the process of electrolytic manganese.The thermodynamic analysis indicated that the sulfur-containing compounds at low valence would form sequentially in the leaching of pyrolusite and pyrite,such as S_x^2-,S,S_xO₃^2-,S_xO₆^2-,SO₃^2-,etc.The results showed that the effect of S₂O₃^2-on the current efficiency is particularly significant.The current efficiency of electrolytic manganese drop to 72%from 85%when the concentration of S₂O₃^2-was greater than 0.20 g/L.The SEM diagrams indicated that the globule stack structure of manganese metal was destroyed when the sulfur-containing compounds at low valence were introduced.The electrolytic manganese surface gradually was cracked,and covered a layer of gelatinous sediment which hindered the further deposition of manganese metal.In addition,the presence of these sulfur-containing compounds in electrolyte affects the electrochemical behavior of electrolytic manganese metal.In the electrolysis process,the additional power consumption was required to react with sulfur-containing compounds,which decreased the current efficiency of electrolytic manganese metal.