Silica gel-immobilized Eriochrome black-T as a potential solid phase extractor for zinc (II) and magnesium (II) from calcium (II)

The immobilization of silica gel surface with Eriochrome black-T indicator (ERT) for the formation of silica-ERT phase is described. The surface coverage of silica gel, based on carbon and nitrogen analysis of the modified silica gel phase, is 0.38 mmol g(-1). The stability towards hydrolysis of silica-ERT phase in different buffer solutions (pH 1-10) is studied and evaluated. The applicability of silica-ERT as a solid phase extractor for Zn(II), Mg(II) and Ca(II) is studied by the batch equilibrium technique and found to show an order similar to the formation constant values of these three metal ions with the indicator. The selectivity of silica-ERT phase towards the extraction of a certain metal ion from a mixture containing only two metal ions is studied by the batch equilibrium technique and exhibited good discrimination orders for Zn(II) and Mg(II) in presence of Ca(II). The results of the column separation and preconcentration studies are consistent with the selectivity behaviour of silica-ERT phase, thus affording reasonable separation of the three studied metal ions. (C) 1997 Elsevier Science B.V.