Study On Selective Extraction Of Copper Powder From Electrolytic Sludge Leaching Solution With Electrolysis Under Super Gravity Field

The plating sludge was generated by the precipitation treatment of wastewater during the electroplating process.Due to the existence of heavy metals,the plating sludge was hazardous solid waste to the enviroment.On the other hand,the plating sludge is with rich copper,nickel and other metals,which makes it a valuable secondary resource.The hydrometallurgical process was the main route for the utilization of electroplating sludge.However,the concentrations of metal ions in the leaching solution were very low.In addition,multiple metal ions coexisted in the leaching solution,such as copper,nickel and other metal ions.With the depletion of the copper ions during the preparation of metal copper by electrolysis from the leaching solution,the copper ion concentration decreased rapidly,leading to severe concentration polarization.Resultantly,the co-deposition of impurity metals and metal copper took place in the electrolysis process,leading to the purity decrease of electrolytic copper prepared from the leaching solution.Currently,for such leaching solutions with low concentration and polymetal ions,the treatment were usually to obtain copper by extraction-electrowinning separation or prepare crude products by precipitation,there were problems that the process is long and the product added value is low in these methods.In this study,a short process of separating high purity copper powder by direct selective electrolysis from the electroplating sludge leaching solution was proposed by using the new technology of electrolysis under super gravity field.The feasibility of the new process was explored by theoretical analysis and experimental verification.It was found that the ?j could be increased by the increase of ?? under super gravity field,to improve the selectivity electrolysis for copper.The ?? was 0.65 V when the gravity coefficient was 62,which was 40% higher than that when the gravity coefficient was 1,which provided a theoretical basis for the new process;In the electrolysis process of the copper-nickel simulated leaching solution,the super gravity could enhance the reduction of copper,and inhibit the reduction of nickel and hydrogen,which could enhance the selectivity of electrolytic separation of copper and improve the purity and current efficiency for copper powder.Therefore,the new process was experimentally verified.Aiming at the shortcomings of the existing electrolyzer under super gravity field,a new type of bipolar electrolysis device under super gravity field was designed and developed,which could realize high current transmission,continuous cycle of electrolyte,and on-line collection of electrolysis products.The kinetic characteristics of the electrolysis process were analyzed.The electrolytic test of the simulated leachate was carried out with this apparatus.The purity,current efficiency and extraction rate of copper were greatly improved.Therefore,selective electrolysis extraction of high purity copper powder from leaching solution with the high impurity and low copper content can be achieved by this apparatus.The effects of acid content,current density and super gravity strength on selective electrolytic separation and copper powder properties from the leaching solution were investigated.With the increase of acid content,the purity of copper powder was improved and the particle size of copper powder was more smaller.When the acid content was increased from 5 g/L to 40 g/L,the purity of copper powder obtained after electrolysis for 60 min was increased from 99.54% to 99.93% which could meet the national standard for high-purity copper powder.However the hydrogen reduction reaction was enhanced,leading to the decrease of current efficiency;with increasing the current density,the reduction of nickel and hydrogen were promoted,resulting in the decrease of purity,current efficiency and particle size for the electrolytic copper powder.When the current density was increased from 4.5 A/dm2 to 13.6 A/dm2,the purity of copper powder obtained after electrolysis for 20 min was decreased from 99.98% to 99.86%,but the particle size Dv50 was also decreased from 20.42 ?m to 17.25 ?m.With the increase of super gravity strength,the competition reaction of copper reduction was significantly increased,leading to the increase of purity,current efficiency and copper extraction rate.However,the particle size was also increased.When the supergravity strength was increased from 50 rpm to 100 rpm,the purity of copper powder afterelectrolysis for 20 min was increased from 98.73% to 99.92%,but the particle size Dv50 was also increased from 10.67 ?m to 23.33 ?m.