Displacement And Separation Of Copper Ions In Eutectic Solvents And Its Influence On Zinc Electrodeposition

The deep eutectic solvent is a new type of solvent with high conductivity,wide electrochemical window,good thermal stability,and selective dissolution of metal oxides such as zinc oxide and cuprous oxide.It can be used not only for the electrolytic extraction of metals,and also be used for the selective leaching of zinc oxide,cuprous oxide and lead oxide,and has a very promising application in the extraction and extraction of valence metals.In the process of depositing metallic zinc from zinc-containing leaching solutions using eutectic solvents,the influence of copper is inevitable.Therefore,studying the separation and electrolytic extraction of copper and zinc ions in deep eutectic solvents is important for the recovery and utilization of zinc resources.In this work,choline chloride-urea deep eutectic solvent is used as a solution to study the replacement and separation of copper ions in eutectic solvent and its electrochemical behavior during zinc electrodeposition.The main conclusions are as follows:（1）The thermodynamic and kinetic behaviors of the reaction of copper replacement by zinc powder in the ChCl-urea system were studied.The results showed that the reaction kinetics of this reaction conforms to the electrochemical model of displacement reaction,and the process is controlled by diffusion,and the apparent activation energy of the reaction is 21.6 k J?mol^-1.The reaction is carried out for about 20,000 seconds to reach the reaction equilibrium.The equilibrium concentration of copper ions in the solution decreased with the increase of temperature,and it could be reduced to 20 mg?L^-1 at 373 K.In addition,the equilibrium constant increases with the increasing of temperature,which is conducive to the displacement reaction.The copper powder obtained after the displacement reaction is in nanoscale structure.（2）The effect of Cu（I）ions on the electrodeposition of zinc in ChCl-urea-ZnO was studied.The results show that the presence of trace Cu（I）not only has a depolarizing effect on the reduction of Zn（II）,but also increases the cathode reaction rate.At the same time,it changes the nucleation and growth mechanism of Zn deposition,which also has a certain effect on the purity,surface morphology and lattice orientation of the product zinc.Further increasing the amount of Cu（I）is conducive to the co-deposition of copper and zinc.With the increasing the concentration of Cu（I）,the initial reduction potential of Zn shifts positively,the nucleation and growth mechanisms continue to deviate from the three-dimensional instantaneous nucleation model,and the morphology,structure,and composition of the sediment have also changed significantly.（3）The effect of temperature on the electrodeposition of zinc in ChCl-urea-ZnO was studied.As the reaction temperature increases,the solution resistance and charge transfer resistance gradually decrease,which increases the ion diffusion rate and the cathode reaction rate,and it is conducive to the electrodeposition of copper and zinc.At the same time,the growth rate of grains is accelerated,and the grain size of sediments is increased.