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In this study, sodium polyacrylate (PAAS) and ultrafiltration membranes were used to extract and separate Cu2+ and Ni2+ ions from electroplating wastewater. The effects of pH, the P/M ratio (mass ratio of sodium polyacrylate to metal ions), tartaric acid, and sodium citrate on the complexation of Cu2+ and Ni2+ by sodium polyacrylate were investigated. The retention of Cu2+ and Ni2+ by PAAS in single metal solutions with a P/M ratio = 4 and pH = 5 differed by 45.36%. When the complexation system of PAAS with a single metal contained tartaric acid and sodium citrate, the retention of PAAS for Cu2+ and Ni2+ increased to 80.36% and 58.84%. PAAS retention for Ni2+ decreased, but retention for Cu2+ remained the same. All the results indicated that there was competition between tartaric acid, sodium citrate, and PAAS for the adsorption of Cu2+ and Ni2+. Some of the Ni2+ complexed with PAAS were detached from PAAS complexed by tartaric acid and sodium citrate and permeated through the membrane pores, while the Cu2+ complexed with PAAS was not complexed by tartaric acid and sodium citrate and could not permeate through the membrane pores. Therefore, this study helps to provide a theoretical basis for the separation of Cu2+ and Ni2+ in electroplating wastewater.
Zhang et al. (Thu,) studied this question.