Salicylic acid functionalized polystyrene sorbent amberlite XAD-2. Synthesis and applications as a preconcentrator in the determination of zinc(II) and lead(II) by using atomic absorption spectrometry

Abstract

Amberlite XAD-2 has been functionalized by coupling it through an —NN— group with salicylic acid. The resulting chelating resin has been characterized by using elemental analyses, thermogravimetric analysis (TGA) and infrared (IR) spectra. It has been used for preconcentrating Pb^II and Zn^II, prior to their determination by flame atomic absorption spectrometry. The optimum pH values for quantitative sorption of Zn^II and Pb^II are 5.0 and 4–6, respectively. The two metals can be desorbed (recovery 98–100%) with 1 mol dm^–3 HCl and a mixture of 2–4 mol dm^–3 HCl/3–4 mol dm^–3 HNO₃, respectively. The sorption capacity of the resin is 1146 and 461 µg g^–1 of resin, respectively, for Zn and Pb. From F^–, Cl^–, NO₃ ^–, SO₄ ^2– and PO₄ ^3– ions, only PO₄ ^3– interferes with Pb. The preconcentration factor was found to be 140 for Pb (at 7 ppb concentration level) and 180 for Zn (at 5.5 ppb concentration level). Simultaneous determination of the two metals is possible. Cations commonly present in water do not affect the sorption of both metal ions by the resin. The method was applied to determine Zn and Pb contents of well-water samples (s_r < 7.0%).