Extraction and preconcentration of toxic metal ions from aqueous solution using benzothiazole-based chelating resins

Polystyrene-divinylbenzene resin (PS-DVB) was functionalized with a benzothiazole group. PS-DVB with amino group was initially prepared by nitration and reduction reactions and subsequently treated with ethyl 2-benzothiazolylacetate (BA) to obtain the chelating resin with an amide linkage (BA-PS-DVB). Meanwhile, the amino-PS-DVB was diazotized and coupled with BA to obtain the chelating resin with an azo linkage (azo-BA-PS-DVB). The resins were characterized by elemental analysis and infrared spectroscopy and evaluated for their extraction of Cd(II), Cu(II) and Pb(II) ions in water before their determinations by flame atomic absorption spectrometry (FAAS). Extraction conditions were optimized for batch method such as the pH of the solution, the extraction time and the adsorption isotherm. The optimum pH for the extraction of Cd(II), Cu(II) and Pb(II) are 8.0, 7.0 and 6.0, respectively, while the equilibrium time of all ions was reached within 10-20 min. The adsorption behavior of all the metal ions followed the Langmuir adsorption isotherm. In the column method, the optimum flow rates of metal sorption onto BA-PS-DVB and azo-BA-PS-DVB columns were 2.5 and 4.0 mL min^− 1. Metal ions sorbed onto columns were eluted by 0.5 to 2.0 M HNO₃. The preconcentration factors of Cd(II) and Cu(II) on azo-BA-PS-DVB and Cu(II) on BA-PS-DVB were 50, 50, and 20, respectively. The present column method gave acceptable validation results: 71.2 and 74.0% recovery for Cd(II) and Cu(II) and an overall relative standard deviation (R.S.D) less than 10% (n = 15). The proposed method was applicable for determining Cu(II) in drinking water.