Cupric Oxide Recovery using EOCOR™ from Cupric Chloride Etchant Waste

1. Outline Cupric chloride etchant waste is discharged from the print circuit board manufacturers. The etchant waste is characterized by a very low pH and high cupric ion and chloride ion concentrations. The EOCOR Process is an on-site recycling technology of the cupric etchant waste. And the product of EOCOR Process is cupric oxide which can be used as a raw material of plating process. For on-site recycling technologies one of the biggest challenges is to avoid chloride contamination. The copper plating process requires precise control of the chloride concentration which affects the performance of copper plating. Thus chloride should be removed from recycled copper even though cupric oxide etchant waste contains a much higher concentration of chloride ion as mentioned above. For this reason on-site copper recycling technologies to produce recycled copper with a low content ratio of chloride have become highly desirable. The EOCOR Process can produce the low chloride content CuO because the etchant waste is added stepwisely to the NaOH solution. And according to the optimization of the reaction conditions we confirmed the produced CuO can be used as a raw material of plating process. 2. The process of EOCOR reaction a For CuO recovery the etchant waste and H2O2 solution were mixed and stirred (Process A). b The mixture of etchant waste and H2O2 solution was added to NaOH solution stirring continuously (Process B). c After the stirring of the NaOH solution we repeated stepwise the mixing and addition process till the terminal pH was reached. d The slurry of CuO product was washed with deionized water several times and dried afterwards and the properties of the dried CuO were described. 3. The optimization of the reaction conditions We optimized the reaction condition on laboratory experiment. As the result the final pH of the reaction and the temperature of NaOH solution affect to the chloride content of produced CuO. 4. The pilot scale experiment Based on the optimized conditions established by the lab-scale experiments the on-site trial production of CuO from real cupric chloride etchant waste was carried out at a PCB factory. The operation time per batch was about two hours. The throughput of the trial plant was 55 L of etchant waste per batch. We ran the pilot plant for 14 batches and washed part of the CuO slurry. We then successfully obtained about 20 kg-dry weight of refined CuO powder. The chloride content of the refined CuO powder was measured to be around about 80 mg-Cl/kg-CuO. The removal ratio of copper from the etchant waste was almost 100% since the soluble cupric content of the supernatant was below 2 mg/L. This fact clearly shows that our proposed recycling technology is applicable to actual etchant waste treatment and that the optimized conditions are efficient for actual use. 5. The first practical plant Based on the pilot trial we constructed the first practical plant in Vietnam. The throughput of the plant was 10 t/d of etchant waste. The chloride content of the recovered CuO was 85 mg-Cl/kg-CuO and the plant produced stable CuO for eight months.