Study Of The Copper Electrorefining Feasibility By AC/DC Electrolysis

Copper, which uses very extensive is an important material of modern economic development, Ultra-pure copper (99.999%-99.99999%) with excellent performance, can improve the quality of electronic products, reduce manufacturing costs, and meet the technical requirements of many contemporary cutting-edge technologies. It has been used in many kinds of applications, and achieve good results.Electrorefining is the main method to produce high-pure copper, the most widely used, the largest in practice and the most sophisticated in technology. Among all the methods of ultra-pure copper production in the future, the method of electrorefining should be the most promising. Over the years, the main method of copper production is the DC electrolysis, but due to the limit of limit current density of 280A/m2, copper with acceptable quality can not be obtained at high current density. To enhance the current density of copper deposition, domestic and foreign scientists used ultrasonic method, periodic reverse current method, pulsed current method and others, but these methods above still have some flaws of their own when achieve their intended purpose.AC and DC superimposed is a new kind of power supply, has been preliminary used in gold electrolysis, but so far this type of new power supply has been used in the copper electrorefining by few electrolysis workers. In this paper the new supply is applied to the electrorefining of copper, the amplitude and frequency of the AC on the impact of electrolysis have been determined. The appropriate AC and DC superimposed electrolytic parameters are:the frequency of alternating current for 1000 Hz, the amplitude for 10 mV. Through a large number of experiments, the factors of temperature, acid-copper ratio, distance, current density, electrolysis time and others on the impact of quality and the deposition rate of copper cathode have been systematically studied. The optimum conditions have been determined:the temperature for 50℃-60℃, the distance for 6 cm-8 cm, the copper-acid ratio for 140 g/L:180 g/L, the current density for less than 360A/m2.Compond additives in electrorefining of copper take an important role, a series of new re-formulated compound additives have been made based on a large number of literatures and predecessors'work. Through a great many of experiments, one or two better performing compound additives have been selected. Also their CV (cyclic voltammetry) curves and EIS (electrochemical impedance spectroscopy) curves have been studied. Through analyzing optical microscope photographs, SEM and XRD, the effects of all compound additives on electrorefining of copper by AC/DC have been studied. Meanwhile, combination with electrochemical test results, the mechanism of compond additives have been studied:self-made compound additive XVI and XVII which can enhance the cathode polarization, but can not change the deposition mechanism are two better compound additives, and expected to become new compound additives in the future.When the additive exists, the current density can reach about 360 A/m2 in the case of ensuring the quality of cathode copper. With the time of electrolysis prolonging, the quality of cathode copper can be still improved to some extent. It has some reference for today's copper industry production.