Nan Min Wu - Department of Environmental Engineering and Health, Yuanpei University of Medical Technology, Hsin Chu City, Taiwan
Wen Chin Chen - Department of Environmental Engineering and Health, Yuanpei University of Medical Technology, Hsin Chu City, Taiwan

Waste copper-bearing solution generated from the micro-etching process of printed circuit boards (PCBs) was studied using cementation technology in a chemical recycle plant. Operation parameters include initial copper ion concentrations (15, 23, 30 g/L) and pH values (pH = 1, 2, 3, 4) were assessed. Results showed that, within the range from 15 to 30 g/L of copper ion concentration, the reaction rate decreased with increasing the initial concentration. In addition, the higher the pH value the slower the copper cementation rate. And at pH = 4, the rate is as low as about 40 %, compared to the other pH values. It is attributed that, presumably as the pH of the solution increases, the copper hydroxide may be deposited onto the iron sheet surface to form a passivation layer, resulting in the blocking of solid-liquid interface mass transfer. Results from mass balance calculations indicated that the unit operation of the plant was quite in agreement with expectations. However, the average resource conversion rate (RCR) was at 58.7%. In order to increase the resource conversion rate, it is suggested that either a reduction of water consumption or a water recycling program to the process should be taken into consideration to increase the RCR. The result of this study is beneficial to shorten the gap between theoretical research and practical operations for chemical recycle plant that is positive to industrial waste reduction and resource sustainability.

Micro-etching, cementation technology, passivation, mass balance, resource conversion rate