Separation of Copper and Nickel Metal Ions from Electroplating Wastewater by Ultrafiltration with Tartaric Acid and Sodium Citrate Reinforced Sodium Polyacrylate Complexation.

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.