Removal of Pb(II) ions by means of polyelectrolyte enhanced ultrafiltration

Abstract

Summary — 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/dm 3 ) 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