This study aims to explore economic benefits of copper-containing wastewater and sludge recovery in copper plants. Electrodeposited (ED) copper foil whose productivity of Taiwan ranked the top one in the world, is the key raw material of printed circuit board (PCB), and PCB is the second largest electronic components industry in Taiwan.
Recovery of copper-containing wastewater and sludge is one of the important issues of industrial development, no matter if the perspectives are economic benefits, water resource or environmental protection. A recovery system usually adapted in Taiwan ED copper plaints today was never mentioned before in literatures, and it consists of two parts: First, combining reverse osmosis (RO), vacuum evaporation, ion-exchange processes to recovery the copper-containing wastewater. Second, selling copper sludge to resource recovery companies. These companies could recover the copper from sludge by pyrometallurgy refining. Consequently, the recovery of copper-containing wastewater and copper sludge are not only technology issues, but also refer to the economic benefits of copper plants, therefore only considering the whole economic picture can understand the practical situation.
In this study, costs/benefits of copper plants and resource recovery companies respectively in treatment process of copper-containing wastewater and copper sludge were calculated. This cost-benefit analysis suggested a new design of wastewater treatment process. The effects of wastewater reduction on copper sludge concentration, sludge selling price and whole economic benefits were also estimated respectively. Besides, the possibilities of total/further wastewater recycling and the corresponding sludge treatment methods were also discussed.
This study carried out two suggestions for copper plant. First, copper plants should establish pyrometallurgy refining process in plants, which brings more benefit rather than selling copper sludge to recovery companies. Second, ion-exchange methods should replace RO process to concentrate copper-containing wastewater before further condensation by vacuum evaporation, where chelating ion-exchange resin with high concentration ability can reduce the major cost of wastewater treatment, the electricity fee of vacuum evaporation.