Polymer assisted ultrafiltration for copper-citric acid chelate removal from wash solutions of contaminated soil

The removal of heavy metals from aqueous systems such as wash-solutions of contaminated soil by using Polymer-Assisted Ultrafiltration (PAUF) has been studied. For the extraction of metal ions from contaminated soil citric acid is used as a chelating agent. Cu2+ as metal ion and the polymer polyethylenimine (PEI) as ligand were used in the various experiments. Optimal chemical conditions for copper complexation by citric acid were determined by means of complexation tests. The results showed that citric acid is able to chelate copper ions at pH 5.5, while decomplexation occurs at pH <= 2. Maximumbonding capacity ( saturation condition) was 0.625 mg Cu2+ permg citric acid, meaning 2 mol Cu2+ per mol citric acid. Complexation tests in the system polyethylenimine - citric acid - copper showed that the polymer is able to complex the copper - citric acid chelate at pH = 6 while release occurs at pH < 3. The saturation condition was 0.333 mg Cu2+ per mg PEI. The ultrafiltration tests, carried out at three trans-membrane pressures (2, 3 and 4 bar), showed the possibility of using the PAUF technique for copper ion removal from aqueous solutions.