SEPARATION BY COUPLING ULTRAFILTRATION AND COMPLEXATION OF METALLIC SPECIES WITH INDUSTRIAL WATER-SOLUBLE POLYMERS - APPLICATION FOR REMOVAL OR CONCENTRATION OF METALLIC CATIONS

Metallic cations are complexed by industrial water soluble polymeric ligands, derived from polyacrylic acid, which are usually employed in water treatment. A knowledge of the physical properties such as solubility, basicity and stability constants of the formed complexes is useful to test the coupling of complexation and ultrafiltration across a polysulfone membrane in order to concentrate or separate metallic species. The influence of several parameters including pH and ligand concentration is discussed; optimal operating conditions can be obtained with simple equilibrium calculations. In this work the complexation-ultrafiltration process is applied to remove Ag+ from a waste solution containing large amounts of Cu2+; results show that the difference between the stability constants of the complexes is sufficient to separate Ag+ and Cu2+ efficiently. However with a dilute mixture which contains Ni2+ and Cd2+, it is only possible to concentrate the metallic species because the specificity of the investigated ligand is too low.