Speciation of Cr(III) and Cr(VI) by Porous Nano-Barium-Strontium Titanate and Flame Atomic Absorption Spectrometry

Abstract

A sensitive method has been developed for the speciation of Cr(III) and Cr(VI) in natural water using a porous nano-barium-strontium titanate by sorghum straw template method (SPBST) and flame atomic absorption spectrometry (FAAS). The procedure presented based on Cr(III) and Cr(VI) show different adsorption capacities on the SPBST at different pH values, that is, Cr (III) selectively retained at pH 13, but Cr(Ⅵ) can’t be adsorbed. Whereas Cr (VI) retained at pH 1, but Cr(Ⅲ) can’t be adsorbed. Hence, Cr(Ⅵ) and Cr(Ⅲ) can be separated through changing pH value of medium. Cr(Ⅵ) and Cr(Ⅲ) adsorbed on the SPBST can be completely eluted using 1•0 mol•L−1 NaOH and 1.0 mol•L−1 HCl, respectively. And Cr(Ⅵ) and Cr(Ⅲ) were determined by FAAS, The preconcentration factor of the method was 100. At the optimum conditions determined experimentally, the adsorption capacities were calculated to be 21.6 mg•g−1 and 7.3 mg•g−1, respectively. The proposed method was applied to the determination and speciation of chromium in tap water, lake water and wastewater samples with satisfactory results.