Research On The Key Technology Of Electrolytic Manganese In Chlorine Medium

The electrolytic metal manganese industry is a highly energy-consuming industry.90%of the energy consumption in this industry is in the process of electrodeposition of manganese.At present,most manganese is produced using a sulfate electrolyte（MnSO₄-（NH₄）₂SO₄）system.However,the sulfate electrolyte electrolysis process has the problems of low current efficiency and high energy consumption.So another electrolytic system,the chloride electrolyte（MnCl₂-NH₄Cl）electrolytic manganese attracted the attention of many researchers.The use of chloride electrolytes has the advantages of high electrical conductivity,low electrolytic voltage,and high current efficiency,which can greatly save energy.However,chlorine gas is generated in the anode during the electrolysis process,which causes great harm to the production and has not been used commercially.In addition,although China is the world’s largest manganese resource utilization country and has more reserves of manganese ore,a large part of China’s manganese ore resources are rhodochrosite which is accompanied by chlorine impurities.The current use of this type of manganese ore is mainly to study the removal method of chloride ions,but there is currently no complete process for removing chloride ions,which leads to the inevitable inclusion of chloride ions in the electrolyte,which affects production and makes this type of manganese ore The utilization rate is low.In view of the above problems,this paper starts from the aspects of comparison between sulfate and chloride systems,optimization of electrolysis manganese process parameters of chloride system,anode chlorine evolution reaction and reduction of chlorine gas,and dynamic cycle test of electrolysis manganese chloride system.The development of electrolytic manganese in chloride system and the efficient use of chlorinated manganese ore.Through experimental research,we have obtained the following valuable conclusions:（1）In terms of physical and chemical properties,the electrolyte of the chloride system has lower density and higher conductivity than the sulfate system;in terms of electrochemical behavior,when the current density is greater than 50 mA·cm²,the ammonium chloride solution Shows more vigorous hydrogen evolution behavior,indicating that the chloride system is not suitable for using high current density;both SO₂ and SeO₂ can greatly improve the current efficiency of manganese deposition;electrodeposition experiment results show that under the same deposition conditions,whether it is added SO₂ Still SeO₂,the deposition efficiency of the chloride system is higher than that of the sulfate system,and the tank pressure is always lower than that of the sulfate system.（2）By analyzing the current efficiency of the cathode plate,the apparent state of the electrolytic manganese and the microscopic morphology,the best process formula for the electrolytic manganese of the selenium-free chloride system is:the concentration of manganese ions is 20 g/L,and the concentration of NH₄Cl is 2 mol/L,SO₂concentration is 0.15 g/L,catholyte pH is 7.25,current density is 50 mA/cm²;by examining the chemical composition of electrolytic manganese,on the basis of selenium-free electrolytic manganese formula,add 10 ppm SeO₂,you can get the purity of 99.8%of electronic grade metal manganese,and the deposition efficiency can reach more than 88%.（3）The study of the anode process found that the amount of chlorine gas decreases with the increase of the current density and increases with the increase of the ammonium chloride concentration.The presence of Mn²⁺has an inhibitory effect on the precipitation of chlorine gas;The redox reaction of chlorine gas prevents the overflow of chlorine gas.Therefore,the longer the diffusion path of chlorine gas,that is,the farther the plate is away from the liquid surface,the more chlorine gas is reacted by the ammonium ion,and the less the amount of chlorine gas overflows.If the ratio of electrode area to solution volume close to industrial production is used,even if the electrode is submerged into the solution up to 5 cm,there will still be chlorine overflow;for this,try to use a mixed salt system composed of chloride and sulfate for manganese deposition,which can be further Reduce the amount of chlorine gas overflow,and retain the advantages of chloride medium manganese deposition efficiency is high.（4）The results of the dynamic cycle test of electrolytic manganese in chloride system under near industrial conditions show that:in terms of chlorine gas overflow and manganese deposition efficiency,the mixed salt system has little difference in manganese deposition efficiency compared to pure chloride system,but the chlorine gas overflow The volume decreased significantly.In terms of the quality of manganese deposition,when the additive is SO₂,the quality of the deposited manganese in the mixed salt system is poor,and when the additive is the composite additive（SeO₂+SO₂）,the mixed salt system exhibits better manganese deposition quality.Regardless of whether the additive is SO₂ or a compound additive,the tank pressure of the mixed salt system is higher than that of the pure chloride system.