Resources Recovery By The Combined Technology Of Electrolysis And Electrodialysis From Copper Wastewater

In this paper, the feasibility of combination technique of electrolysis and electrodialysis on copper wastewater was investigated in order to recovery copper as well as water resources. As we know, electrolysis is suitable for high concentration of heavy metals wastewater with the ability of heavy metals recovery; however, the tail water quality of electrolysis cannot satisfy with the discharge standard. Moreover, electrodialysis usually does well in low concentration of heavy metals wastewater. With the reuse of diluted water, the part of concentrated water needs to be further treated. The combination technique combines the advantages of electrolysis and electrodialysis, getting rid of their disadvantages at the same time, and realizing the recovery of copper and water.The treatment of combination technique on copper wastewater generated from acidic copper electroplating wastewater was investigated at different operating parameters including voltage, initial concentration of copper and water flow. The effects of these parameters on copper recovery and outlet water quality were discussed respectively.As the results of electrolysis show, the dynamic electrolysis process fits better for the requirements of practical application. Besides, the higher voltage, the higher initial concentration of copper and the smaller water flow can do a better treatment. The energy consumption increases with the increasing voltage and initial concentration of copper, while decreases with the larger water flow. However, high voltage results in a low economy and low water flow declines the efficiency of treatment. Take the effects, efficiency and energy consumption into consideration, with 2~2.5V voltage, 6L/h water flow, the electrolysis setup of combination technique can be capable of about 500mg/L copper wastewater, which comprised of raw wastewater and concentrated water generated from electrodialysis process. The copper recovery is over 90 percent, the purity of copper is 99 percent, the energy consumption is 2~7kW·h/kg. Compared with the price of copper recovery, 30~120 Yuan/kg will bring the industry much interest. Additionally, the morphology differs from current density. High current density got loose copper powder while low current density got lucent copper flake. According to the requirements of copper recovery company, we can change different operations to get the corresponding copper.In the electrodialysis part, the setup can treat low concentration of copper wastewater (<200mg/L), which includes the electrolysis tail water. The effects of diluted were better with higher voltage and lower initial concentration of copper. The concentration of copper of diluted water was in the range of 0.5~2.0mg/L, the conductivity was under 200μs/cm, pH values were in 3~4, the water recovery rate was 75~93 percent. The concentrated water (about 500mg/L) produced by electrodialysis can be sent to the electrolytic cell for further recovery.The combination technique can treat either low concentration of copper wastewater, or high concentration of copper wastewater, or both of them at the same time, realizes the zero discharge. However, the capacity of daily treatment is small, which is suitable for small electroplating industries. Moreover, as the components of actual copper wastewater are variable and complex, how to improve the copper purity and recover other heavy metals is still necessary to fix up in the future research.