| Metal manganese(Mn)is a strategically important resource in China,which are mainly produced by the direct current electrolysis method.With the development of electrolytic manganese industry,the grade of manganese ore resources continually reduces,the composition becomes complex and the comprehensive utilization of manganese resources is relatively low.These problems limit the development of electrolytic manganese industry in China.The efficient utilization of low-grade complex manganese resources plays a key role in the manganese industry.In this paper,the leaching and electrolysis processes of low-grade complex manganese resources have been studied based on the chemical engineering process intensification method,nonlinear dynamics theory and surface chemistry principle.The details are as follows:(1)Hydrometallurgical leaching process intensified by electric field for leaching manganese from low grade manganese dioxide ore was developed to increase the leaching efficiency of manganese.The leaching process,kinetics,and mechanism were studied.The results showed that there were different interactions among various leaching factors and the leaching efficiency can reach 96.7% after intensified by electric filed.The leaching process conformed to the shrinking core model and the reaction rate was controlled by diffusion through a product layer.The macroscopic kinetic equation of the leaching process is (?).During the leaching process,the newly formed Fe3+ that generated from the oxidation of ferrous on manganese dioxide surface was reduced to Fe2+ by electric field to keep the Fe2+ at a high level in the solution.The cycling of Fe3+ and Fe2+ ensured the high leaching efficiency of manganese during the process.(2)The removal method of chlorine from manganese ore and the effect of chloride ion on the electrolysis process were studied based on nonlinear dynamics theory.The results indicated that the removal efficiency of chlorine was 96.6% and the manganese grade was 42.1% by alkaline pretreatment of sodium carbonate.Compared to the direct water washing,the removal efficiency of chlorine and manganese grade increased by 22% and 2.7%,respectively.Cl-has an inhibitory effect on the electrochemical oscillations on the anode.The addition of Cl-in the electrolysis system can improve the current efficiency and reduce the electrolytic energy consumption.On the anode,Cl-may transform to Cl O-,Cl O2-,Cl O3-,Cl O4-etc.,and these oxygen content of chlorine can convert the low valence to high valence state,break the presence and circulation of manganese species at intermediate valence,and form dense amorphous compounds on the anode,thereby inhibit the generation of electrochemical oscillations and strengthen the energy saving of electrolysis process.The idea of the effect of chloride ion on the electrochemical oscillations of the electrolysis process provides a new thought and theoretical support for the energy-saving electrolysis process.(3)Based on surface chemistry the manganese leaching process,manganese residue filtration process and electrolysis process were studied.The results indicated that TJ-A can reduce the surface tension of the solution,improve the wetting effect of the solution on the manganese ore and enhance the contact between the manganese ore and the sulfuric acid,as well as improve the leaching rate.During the filtration process,TJ-A adsorbed the microporous cracks on the surface of the manganese slag to increase the additional pressure generated on the liquid surface and improve the permeation effect of the manganese slag,so that the free water in the manganese slag was successfully removed from the manganese slag,thereby reducing the moisture content.After adding TJ-A,the moisture content of manganese slag dropped from 31.3% to 22.9%.The addition of TJ-A can reduce the surface tension of the electrolyte,improve the electrolyte conductivity and reduce the free energy of the system.When the solution surface tension was 52 m N/m after adding TJ-A,the current efficiency can improve from the original 82.18% to 86.33%,the power consumption reduced from 5990.6 k W·h to 5502.7 k W·h per tons of manganese.(4)Multi-field coupling enhancing electrolytic manganese efficient and energy-saving process were studied based on multi-field coupling basic principles and methods.When the aperture was similar,the cathode overpotential,electrolyte potential and the anode current distribution are different because of the different pore shapes.The experiment and simulation results showed that using the round-hole anode the cathode potential was the most negative,electrolyte potential distributed evenly and the current efficiency was the highest.Pulsed electrolysis method was helpful to suppress the evolution of hydrogen,reduce the amont of anode slime and obtain dense and meticulous metal manganese products.The current efficiency can reach 88.3% when using pulsed electrolysis method.Compared with the DC electrolysis,the current efficiency is improved by 8.72%,anode slime reduced by 55.5%.Compared with the direct current electrolysis,the pulsed electrolysis can improve the tolerance of impurity ions Cu2+,Co2+,Ni2+ and Zn2+ to different degree.(5)A pilot study on the recovery of manganese from low concentration manganesecontaining wastewater was carried out.The stability,feasibility and economy of the continuous operation of the process were analyzed.Experimental results showed that the process performed good continuity and stability.The impurity removal and electrolysis process have good stability,manganese loss was small.In the continuous test,the recovery efficiency of manganese in the first and secondary impurity removal process was 97.68% and 93.87%,respectively.In the electrolysis process,recovery efficiency of manganese was 86.74%(including anolyte,anode slime,etc.)and the metal manganese recovery efficiency was 51.80%.Metal manganese products can meet the electrolytic manganese industry standards(YB/T051~2003)DJMn II.Through the analysis,the treatment of the waste water by Ca O inllustrates the consumption of 19.44 yuan/m3,and treatment of the waste water by electrolytic process can be profitable 20.88 yuan/m3.Due to the amount of waste water was 400,000 m3 per year,the electrolysis annual economic efficiency is 16 128 000 yuan/year.This process can realize the recovery of manganese resources in the low concentration manganese-containing wastewater and achieve the treatment of waste water while recovering the manganese metal. |
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