Polymer Enhanced Ultrafiltration Wastewater Treatment

Wastewater contains heavy metals are harmful because of their higher toxicity. The process of complexation-ultrafiltration can recycle the heavy metals from wastewater of low concentration, through separating and concentrating the water. Hence it has a positive significance to reduce environmental pollution and can turn waste into treasure.Copolymer of acrylic acid and maleic acid (PAM-100) was used as complexing reagent for the treatment of wastewater containing Cr(Ⅲ), Cu(Ⅱ), Ni(Ⅱ), Cd(Ⅱ) by ultrafiltration respectively. Effects of mass ratio of polymer/metallic ions (P/M), pH, time, salt concentration on the retention of Cr(Ⅲ), Cu(Ⅱ), Ni(Ⅱ), Cd(Ⅱ) and permeate fluxes were investigated. Results indicate that the retentions of Cr(Ⅲ), Cu(Ⅱ), Ni(Ⅱ) and Cd(Ⅱ) depend strongly on P/M, pH and salt concentration. The retentions of metal ions increase with the increase of pH at a certain P/M, and increase with the increase of P/M value at a certain pH. The rejection of metal ions is greater at pH=5.0, P/M=7 for Cr(Ⅲ), P/M=6, pH=5.3 for Cu(Ⅱ), pH=6.0, P/M=7 for Ni(Ⅱ),and pH=5.8, P/M=6 for Cd(Ⅱ). The retention of metal ions is influenced by salt concentration, the retention decreases with the addition of NaCl and Na2SO4. In addition, the retention of metal ions decreases with the addition of competitive complexing reagent with small molecular weight.Furthermore, selective separation for Cu(Ⅱ), Ni(Ⅱ) are also studied, by the comparison of the two mixed metal ions solution with the single-ion solution retention. The results showed that:mass ratio of polymer/metallic ions (P/M), pH significant effect on selective separation. The copper, nickel ion selective separation coefficient S reached more than 260 at a mixed solution of P/M=3, pH=5.3. The presence of the addition of NaCl and Na2SO4 can affect the interaction between metal ions and the complexing reagent,thus achieving the separation between the two.