The Preparation Of High-purity Copper By Electrorefining In Nitrate System

With the development of science and technology, the application of high performance copper is gradually expanded. On the basis of copper and copper alloy materials,high-purity copper with its excellent conductivity, thermal conductivity and good ductility is widely used in integrated circuit interconnect, thin film solar cell, high fidelity speaker cable, fatigue resistant cable and other fieldsThe preparation methods of high-purity copper mainly include electrorefining, zone melting method, ion exchange method, vacuum electron beam melting method and so on. Electrolytic refining method as the basic and commonly used method, its stable production process is very important, which can bring a lot of convenience for the further processing. At present, electrolytic refining process mainly consists of sulfuric acid system and nitric acid system: the technology of sulfuric acid system is ripe, which is widely used in the industrial production. But due to its own condition, sulfuric acid system unable to meet the higher requirements on copper purity; nitric acid solution does not have the limit, but the presence of NO3-will influence the stability of electrolysis production. Although we do a lot of researches on it, there is no perfect electrolytic technology. This paper aims at the stable production technology of high-purity copper in nitrate system.This thesis adopts the method of electrorefining to produce high-purity copper in nitric acid system, using Ti plate as the cathode and4N copper as anode. Studing the effect of the cycle, current density, the value of pH, copper ion concentration and temperature on the quality of cathode copper, and then deciding the optimum technological conditions. The research shows that:using the up-lower circulation mode, when the current density is100-200A/m2, the value of pH is0.5-2.0, the concentration of copper ion is50-60g/L, temperature is20-30℃,we can make the electrolysis production stable. The surface of cathode copper is compact, the analysis of cathode copper by GD-MS shows that the impurity content is0.85×10-4%, the purity reaches99.9999% The experiment finds:when electrolysis under high current density, the nitrate ion can discharge in the cathode, leading to the accumulation of nitrogen oxides in the electrolyte and unstable production. In order to avoid this phenomenon, we use the low current density, and regularly add hydrogen peroxide to the electrolyte. The adding cycle of hydrogen peroxide is3-7days when the current density is150A/m2, with a dosage of0.5-1.0mL/L. In order to keep the ion concentration in the electrolyte, we need to periodically discharge the old liquid and add new liquid, the addition is based on the variation of copper ion.