Effect Of Aluminum-nickel On The Dynamic Behavior Of Anode And Cathode In Copper Alloy Electrolysis

Due to the depletion of copper-rich primary ores and the increasing requirement,reuse and recovery of copper from secondary sources have always attracted considerable attention.Copper based alloys have widespread application depending on combination of good corrosion resistance,excellent electrical conductivity and attractive mechanical properties,and an increasing emphasis has been placed on the recovery of valuable metals from scraps of them.Recovery of valuable metals using direct electrolysis is a comprising process regarding the economy and the environment,and several related processes have been developed.In Chile,anode support system has been used in industrial electro-refining of copper scrap and blister copper granules claiming an energy saving as high as 50%.Recent studies from Wang,F.et al.showed that pure copper(99.98%)could be obtained from the anodes cast from Cu-Ni based alloy scraps.Further investigation,we have studied the electrochemical dissolution of aluminum bronze in CuSO4 electrolytes,and kinetic investigation of copper electrodeposition from copper and nickel sulfate solutions.Firstly,the electrochemical behavior of the aluminum bronze in simulated electrolytes like those used in the industrial copper electrolysis process was investigated.Conventional electrochemical techniques including polarization techniques and electrochemical impedance spectroscopy were used.The alloy was found to be easier dissolved when the CuSO4-H2SO4 electrolytes contained sulfuric acid concentration of 160 g/L.A higher sulfuric acid concentration led to increase of polarization resistance and electrolyte resistance,and further the decrease of corrosion current density.The activation energy of the dissolution process was found to be 27 kJ/mol assigning a diffusion controlled reaction.The impedance measurements and impedance data fitting to equivalent circuit models showed that the passive film formation proceeded via a dissolution/precipitation mechanism under open circuit condition.Secondly,a systematic study of the influence of nickel ions on copper electrodeposition from acidic sulfate solution has been performed in order to obtain information about the kinetics of the cathode process.The study was based on electrochemical investigation using cyclic voltammetry and polarization measurements.When Ni2+>20 g/L,the results from cyclic voltammetry measurements indicated that presence of nickel ions depolarized obviously on the copper electrodeposition.Kinetic parameters such as Tafel slope,transfer coefficient and exchange current density obtained from Tafel plots led to the conclusion that the nickel ions unaffected on the mechanism of copper electroreduction but improved dynamic condition.In addition,the presence of nickel ions inhibited the cathodic diffusion of copper ions,which would lead to the decrease in cathode peak current density and limiting current density for copper electrodeposition.