Application of PEUF to competitive separation of Cu(II) and Cr(VI) from aqueous solutions containing chloride or sulphate ions

The paper addresses the separation of Cu(II) and Cr(VI) ions from their binary mixtures by polymer enhanced ultrafiltration (PEUF). The tests were performed with solutions containing two types of anions: chlorides and sulphates. Polyethyleneimine (PEI), a water-soluble polymer containing amino groups, was used to aid the ultrafiltration separation of metal ions. The main parameters affecting the process effectiveness investigated herein included the composition of bi-ionic Cu(II)/Cr(VI) mixture, pH, polymer–metal molar ratio C_PEI/C_M and the presence of chloride or sulphate anions. The rejection coefficients of the metals in various process conditions were analysed, and the possibility of simultaneous separation of Cu(II) and Cr(VI) ions from the solutions as well as selective separation of one metal from the bi-ionic mixture was discussed.