Successive concentration and purification of simulated nickel-electroplating rinsing wastewater was carried out by integrating membrane process with electrodeionization.The concentrate compartments were filled with ion exchange resins to enhance the separation.The concentrate stream of the primary EDI procedure was operated in closed circuit circulation.The influence of the volumetric ratio of resins in concentrate compartments on the separation was examined.It was found that the best performance could be achieved when anion to cation resin ratio of 6∶4 was adopted.With feed Ni2+ concentration of 50 mg·L-1 and pH of 4.25,the Ni2+ concentration of effluent dilute stream could reach 2.78 mg·L-1 while that of the effluent concentrate stream was as high as 11171 mg·L-1,which gave a concentration ratio of higher than 220.The effluent dilute stream of the primary EDI was then sent to the second EDI stack for deep desalting.Dilute product with resistivity of 1.6—2.0 MΩ·cm was then obtained,which could be recovered as pure water for electroplating.The membrane process integrated with EDI could find its potent role for zero emission and resource reuse of heavy metal wastewater.
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