Electrolytic Separation Of High Lead-antimony Alloys In Choline Chloride-ethylene Glycol Deep Eutectic Solvent

A large number of high-Pb Sb alloys will be produced in the smelting process of jamesonite.As one of the important raw materials for the production of refined Sb,the effective separation of high-Pb Sb alloys is of great significance to the comprehensive utilization of resources.The existing electrolytic separation methods of high Pb Sb alloy include high temperature molten salt electrolysis and aqueous solution electrolysis,but there are corresponding shortcomings.High temperature molten salt electrolytic separation has high requirements for equipment,and side reactions will occur to reduce the purity of cathode products;the electrolyte composition of aqueous solution electrolytic separation is complex and corrosive to the equipment.Deep eutectic solvents(DESs)are a new type of green solvent.Compared with high temperature molten salt and aqueous solution,the electrochemical separation of high-Pb Sb alloy in DESs has has many advantages,such as the simple synthesis,wide electrochemical window,less corrosion to equipment and no waste products.Using DESs as electrolyte for electrolytic separation of high-Pb Sb alloy is expected to overcome the above problems of high temperature molten salt electrolysis and aqueous solution electrolysis,and improve production efficiency and avoid environmental pollution while ensuring product quality.This study provides a theoretical basis for the industrial application of electrolytic separation of Sb from high-Pb Sb alloy.In this paper,the choline chloride-ethylene glycol deep eutectic solvent(ChCl-EG DES)is synthesized.The solubility of SbC13 and PbCl2 is determined,and the effects of temperature and concentration of SbCl3 on the viscosity and conductivity are studied.It is found that the solubility of SbCl3 and PbCl2 in ChCl-EG DES is 0.2197 mol·L-1 and 0.0074 mol·L-1 at 343 K,respectively.The viscosity of SbCl3+ChCl-EG DES decreases with the increase of temperature,increases with the increase of SbCl3 concentration,and the conductivity is on the contrary.The electrochemical behaviors of Sb/Sb(?),Pb/Pb(?)and high-Pb Sb alloys in SbCl3+ChCl-EG DES are studied by linear sweep voltammetry.The anode polarization test results of metal Sb and Pb show that in ChCl-EG DES,the initial oxidation potential of metal Pb is about 0.45 V less than that of Sb,and the Pb(?)after Pb anode dissolution will form PbCl2 with Cl-in the system.In SbCl3+ ChCl-EG DES,the oxidation rates of Sb and Pb increase with the increase of temperature and decrease with the increase of SbCl3 concentration.The dissolution rate of Sb is faster than that of Pb at low temperature and high SbCl3 concentration.The anodic polarization test results of high Pb Sb alloy show that the temperature range of 323?343 K is conducive to the dissolution of high Pb Sb alloy.The cathodic polarization curves show that in SbCl3+PbCl2+ChCl-EG DES,the initial oxidation potential of Sb and Pb is very close,while the initial reduction potential of Sb(?)is much higher than that of Pb(?).The reduction mechanism of Sb on Ti electrode is studied by cyclic voltammetry and chronoamperometry.The results show that Sb(?)are reduced to Sb in one step on Ti electrode.The diffusion coefficient of Sb(?)increases with the increase of temperature and SbCl3 concentration,which is beneficial to the reduction of Sb,but the effect of temperature is more significant.The early nucleation mode of Sb on Ti electrode is between 3D instantaneous nucleation and 3D continuous nucleation.Based on the above theory,the effects of temperature,current density,SbCl3 concentration and electrolysis time on the electrolytic separation of high-Pb Sb alloys are studied.The results show that the current efficiency increases with the increase of temperature,and increases first and then decreases with the increase of current density,SbCl3 concentration and electrolysis time.The specific energy consumption decreases with the increase of temperature and electrolysis time,and increases with the increase of current density and SbCl3 concentration.The impurity of Pb content in the cathode products decreased first and then increased with the increase of temperature and SbCl3 concentration,while with the increase of current density and the prolongation of electrolysis time,the content of Pb in cathode products increased.In 343 K,30 mA·cm-2 and 0.15 M SbCl3+ChCl-EG DES,the purity of Sb powders obtained from electrolytic separation of high-Pb Sb alloy for 5 h is as high as 99.980%,current efficiency is 93.57%,and unit power consumption is 749.18 kW·h·t-1.The morphology of Sb powders obtained by electrolytic separation of high-Pb Sb alloy is cluster and irregular dendrite.