| It is great importance for tin smelting in the smelting of nonferrous metals.The pyrometallurgy is widely used in tin smelting nowadays,which includes four steps:preprocessing,reduction smelting,slag smelting and coarse tin refining.The coarse tin produced by the reduction smelting from tin concentrate contains more impurity lead,which must be treated by fire or electrolytic refining and then fine tin products can be obtained.Electrolysis refining,including acid and alkaline aqueous solution,has the disadvantages in corrosivity,volatility,regular supplement of electrolyte.The deep eutectic solvent?DESs?has excellent physical and chemical properties so that it can be used as electrolyte in the electrolytic separation of Sn-Pb alloy.In this paper,the relevant basic theory research about electrolytic separation of Sn-Pb alloy in DES has been carried out,which could enrich and develop the application of deep eutectic solvent in metallurgy.In this paper,a certain amount of SnCl2·2H2O was dissolved in choline-glycol deep eutectic solvent?1ChCl:2EG DES?,which was used as electrolyte named SnCl2·2H2O/[1ChCl:2EG]DES.The physicochemical properties of the solution,such as density,viscosity,conductivity and thermal stability,were studied and the solubility of SnCl2·2H2O in 1ChCl:2EG DES was also measured.The result showed that the density and viscosity of the system decreased with the increase of temperature,and the conductivity increased with the increase of temperature and the increase of the concentration of SnCl2·2H2O.The solubility of SnCl2·2H2O in 1ChCl:2EG DES was112.5g/L,and the conductivity of 0.1M SnCl2·2H2O/[1ChCl:2EG]DES was 2.143mS/cm,and the viscosity was 12.93 mPa·s.The thermal analysis and infrared spectrum test showed that the DES has a stability within the temperature of 129?.The electrolysis experiment took 0.1MSnCl2·2H2O/[1ChCl:2EG]DES as the electrolyte,the Sn-Pb alloy as the anode and the copper sheet as the cathode.The results showed that:when the Sn-Pb?5%?alloy as anode,the current density was6mA·cm-2,the electrolyte temperature was 50?,The electrolysis time was 6 h and stirring speed was 500r·min-1,the dendritic tin power on the cathode?the purity was99.9801%?could be obtained.When anode lead content increased from 5%to 20%,and the electrolysis time extended to 40h,the cell voltage increased within 25%,but the purity of cathode tin was above 99.95%.The research on the anodic dissolution process showed that the lead was passivated in-0.23V?vs.Ag?,which contained three stages of activation region,transition region and stable passivation,and then the current was reduced to 0.Metal tin only had a slight pseudopassivation,and no passivation occurred.The metal tin was verified to enter the electrolyte in the form of Sn2+through the Kulun method.It was showed that the redox process of Sn2+/Sn is a quasi reversible process controlled by diffusion through the study on the electrochemical behavior of SnCl2·2H2O/[1ChCl:2EG]DES.By studying the nucleation and growth mechanism in the early stage of metal tin electrocrystallization,it was founded that metal tin growed in three dimensional instantaneous nucleation mode,and the increase of potential was beneficial to increase the density of nuclei and to refine grain size. |
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