This work is focused on polyelectrolyte enhanced ultrafiltration as an effective heavy metal separation technique. Three types of effluents, containing Zn(II), Cu(II) and Ni(II) ions, were subjected to the separation process. Poly(sodium 4-styrenesulfonate) -PSSS, a water soluble anionic polyelectrolyte was used as a metal binding agent. Two Sepa® CF (Osmonics) membranes: EW, made of polysulfone and a modified polyacrylonitrile membrane MW, were used in the ultrafiltration process. The preliminary UF tests were carried out on model solutions with target metal ion concentrations of 10, 100 and 250 mg dm . The main parameters affecting the metal retention (the polyelectrolyte quantity and solution pH) were examined. The values of pH 6 and polymer : metal concentration ratio CPSSS : CM = 7.5 : 1 (mol of mer unit per mol of metal) were selected to perform the galvanic wastewater ultrafiltration-concentration tests. Three types of wastewater containing Zn(II), Ni(II) and Cu(II) ions within the concentration range of 30÷70 mg dm -3 were used in the investigations. Very high metal retention coefficients, up to > 99%, were achieved. The retentates obtained were subjected to the decomplexation-ultrafiltration (pH = 1) and subsequent diafiltration step, which enabled partial recovery of concentrated metal ions and the polyelectrolyte. The recovered polyelectrolyte was reused toward Ni(II) ions and the high effectiveness of metal separation has been achieved.
Keywords: polymer enhanced ultrafiltration, heavy metals, galvanic wastewater, polyelectrolyteThe membrane separation processes create new possibilities for the effective purification of galvanic wastewater. One of the most interesting propositions is a polymer enhanced ultrafiltration which combines two processes: metal ions binding with soluble polymeric ligands and retention of resulting macromolecular compounds on an ultrafiltration membrane. Polymer enhanced ultrafiltration has been successfully applied to the separation of metal ions from aqueous solutions, most often Cu, Ni, Zn, Co, Cd, Hg, Cr(III) and radionuclides [1][2][3][4][5][6][7].Basically, two types of polymer used in the process can be distinguished. The first one encompasses chelating polymers, able to form coordination bonds with metal ions, the other includes polyelectrolytes, which have ion-exchange properties. Typical polymers that bind