Preparation of High Purity Copper by Electrorefining in Nitric Acid System
A new process for preparing high-purity copper by electrorefining in a nitric acid system was developed using a 4N copper cathode as raw material.The effects of electrolyte composition on the content of S,Cl,typical positively charged and negatively charged impurities in copper cathodes were investigated.Moreover,the influence of Cu(NO3)2·3H2O raw material purity,electrolyte components(Cu2+,HNO3 and Cl-mass concentrations),and electrolysis period on copper cathode purity,impurity content,current efficiency,and electrical energy consumption was analyzed.The results show that the optimum process conditions are to prepare the electrolyte using 99％purity of Cu(NO3)2·3H2O,with Cu2+mass concentration of 50 g/L,HNO3 mass concentration of 31.5 g/L,Cl-mass concentration of 0.1 g/L,and electrolysis period of 72～120 h.Under the optimal conditions,high-purity copper cathode with purity up to 6N5 and main control impurity elements can meet the high purity cathode copper required by HPCu-6N in the national standard(GB/T 26017-2020).
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