For on-site copper recovery in print circuit board factories, we propose a novel technology to obtain cupric oxide with a low content ratio of chloride from high chloride concentration waste, such as cupric chloride etchant waste. Our technology is designed to avoid formation of double salt and accumulation of cupric hydroxide. In the proposed method, etchant waste mixed with hydrogen peroxide solution is added to sodium hydroxide solution by stepwise addition. We performed lab-scale experiments on the influence of reaction pH conditions on the content ratio of chloride in recovering cupric oxide. The results show that recycled cupric oxide tends to contain a lower content ratio of chloride under higher starting temperatures and higher final pH conditions of the reaction. We also confirmed the optimized conditions; the starting temperature of the sodium hydroxide solution is higher than 70 °C, and the final pH of the reaction is 11.5 to 12. Based on the optimized temperature and pH conditions, we also performed a pilot trial to recover cupric oxide from real etchant waste. Then, we successfully obtained cupric oxide with a content ratio of chloride in 80 mg-Cl/kg-CuO.
Keywords: cupric chloride etchant, cupric oxide, on-site recycling technology, recycling