Study on the adsorption behavior of attapulgite to cadmium(II)and nickel(II)and its analytical application

Based on the characters of high surface area and strong adsorption capacity of attapulgite, a method was established to determine the content of trace Cd(II) and Ni(II) by combining enrichment and separation of attapulgite with flame atomic absorption spectrometry(FAAS)in this paper. The adsorptive behavior of attapulgite to Cd(II) and Ni(II) was discussed while some problems were studied, including the static saturated adsorption capacity, the main factors influencing adsorption and desorption, and the interference of coexisting ions. The adsorption rate of Cd(II)and Ni(II)by 0.50 g of attapulgite was over 94% at pH 4.0 and the metal ions could be quantitatively eluted from attapulgite with 20 mL of hydrochloric acid(0.5 mol/L). Under the optimum conditions, the maximum static adsorption capacity of attapulgite to Cd(II) and Ni(II) were 32.5 mg/g and 25.0 mg/g; the detection limits were 31 ng/mL and 0.19 ng/mL; the relative standard deviations(RSD)were 1.1% and 0.94%(Cd(II):0.3 μg/mL, n=11; Ni(II):0.80 μg/mL, n=11). The proposed method was applied to the determination of Cd(II) in natural water samples and Ni(II) in industrial wastewater. The recoveries were 92%-98% and 87%-102%, respectively.