Recovery of Ni2+ and pure water from electroplating rinse wastewater by an integrated two-stage electrodeionization process

Abstract

The pollution of wastewater with hazardous heavy metals has become one of the most important worldwide environmental problems. In the electroplating industry, large amounts of discharge of untreated dilute rinse wastewater combined with increasingly stringent pollutant emission standards have limited the sustainable development of the electroplating industry. In this study, a novel integrated two-stage electrodeionization (EDI) process for recovering Ni2+ and pure water to reduce pollutant emissions in the electroplating industry was evaluated using a simulated nickel-electroplating rinse wastewater. Based on the characteristic curves, the appropriate operating voltage was determined to be 15 V for the first stage, while the second stage voltage was set at 25 V. The integrated two-stage EDI process removed more than 99.8% of the Ni2+ from the simulated electroplating rinse wastewater, eliminating 94% of the Ni2+ from the feed water (Ni2+ concentration of 50 mg L−1) in the first stage and approximately 96.7% of the remaining Ni2+ in the second stage. Additionally, a closed-circuit circulation of the concentrate stream was used to achieve the solution with Ni2+ concentration as high as 11,031 mg L−1. Pure water with resistivity value exceeding 1.6 MΩ cm was produced by extensive purification during the second stage and was able to be reused as make-up process water. With a treatment capacity of 1.0 m3 h−1, the integrated two-stage EDI process may be able to annually reduce wastewater discharge amounts of 7200 m3 and sludge disposal values of 12.8 tons, generating annual profit of 208,400 Yuan RMB, comparing favorably with existing chemical precipitation process. These results for the treatment of electroplating rinse wastewater suggest that this integrated two-stage EDI process may be economically beneficial with improved environmental benefits.