Retention of Cu(II)- and Ni(II)-polyaminocarboxylate complexes by ultrafiltration assisted with polyamines

The retention of Cu(II)- and Ni(II)-nitrilotriacetic acid (NTA) and ethylenediaminetetraacetic acid (EDTA) complexes in dilute solutions ([M-chelate] = 0.5 mM) by ultrafiltration in presence of polyethylenimine (PEI) or chitosan 10 mM was studied. Metal retentions larger than 98% were observed for PEI in the pH-range of 4-9. The excellent metal retention resulted from the combination of covalent binding and electrostatic interactions. The metal retention was studied at pH 7 as a function of the Cu-chelate/PEI ratio and has shown that the more encapsulating the chelate was, the lower was the retention. Electrolysis at pH 2 was used to precipitate Cu ions and to regenerate PEI with electrolytic yields in the range of 40-50% depending on the mixture composition. (C) 2010 Elsevier B.V. All rights reserved.