SYNTHESIS OF A CHELATING POLYMER MATRIX BY IMMOBILIZING ALIZARIN RED-S ON AMBERLITE XAD-2 AND ITS APPLICATION TO THE PRECONCENTRATION OF LEAD(II), CADMIUM(II), ZINC(II) AND NICKEL(II)

A very stable chelating resin matrix was synthesized by covalently linking Alizarin Red-S with the benzene ring of the polymer Amberlite XAD-2 through an -N=N- group. The resin was characterized by elemental analyses, thermogravimetric analysis and IR and reflectance spectra. One dye molecule was found to be present per repeat unit of the polymer. The resin was used for the preconcentration of Zn(II), Cd(II), Ni(II) and Pb(II) prior to their determination by flame atomic absorption spectrometry (AAS). For the quantitative sorption and recovery of Zn, Cd, Ni and Pb the optimum pH and eluents were pH 5-6 and 4 M HCl or 1 M HNO3 for Zn, pH 5-6 and 4 M HNO3 for Cd, pH 3-4 and 4 M HCl or 2 M HNO3 for Ni and pH 6 and 3-4 M HNO3 for Pb. The sorption capacity of the resin was 511, 124, 139 and 306 mu g per gram of the resin for Zn, Cd, Ni and Pb, respectively. Tolerance limits of NaF, NaCl, Na2SO4, Na-3, PO4, and NaNO3 on the sorption of these metal ions are reported. Sodium nitrate interfered in the sorption of all the metal ions except Pb(II). The preconcentration factor was 40 for all four metals and the lower limit of preconcentration was 0.01 mg dm(-3). The simultaneous determination of all the four cations is possible. The relative standard deviation (R.S.D.) is in the range 3.7-8.2%. Zn, Cd, Ni and Pb in well-water samples were determined by AAS after preconcentrating them with the resin. Ni and Cd were found to be absent. The R.S.D. was 2.7-6.5% and 4.7-10.1% for zinc and lead, respectively.