Removal of Pb(II) ions by means of poly electrolyte enhanced ultrafiltration

This work proposes polyelectrolyte enhanced ultrafiltration to remove Pb(II) from aqueous solutions. Model solutions containing 1-100 mg Pb/dm ³ were used in the research. Poly(sodium 4-styrenesulfonate) (PSSS), which is a water-soluble polymer containing strong cation-exchange groups, was used as a metal binding agent. The process was conducted on a polysulfone membrane with molecular weight cut-off 60 000. The main parameters determining the effectiveness of lead retention (the polyelectrolyte quantity and solution pH) were examined. High retention coefficients (>0.98) were achieved for pH > 4 and 2.5-5-fold excess of polyelectrolyte to metal. Ultrafiltration concentration of Pb(II) solution (50 mg/dm³) was carried out according to the previously determined polymer/metal concentration ratio, and at optimum pH. The lead retention coefficient (R), observed during the process, was within the range of 0.98-0.99. The retentate obtained was used in the next decomplexation-ultrafiltration step (ultrafiltration at pH = 1), which made possible the separation of polyelectrolyte (retentate) and the recovery of 85 % of concentrated Pb ions (permeate). The residual lead, still remaining in the polymer solution, was diafiltred by a 5-fold amount of water acidified to pH = l.