Modified Organobentonite with Dithizone as Adsorbent for Thallium(I) in Water

Abstract

Adsorption capability of Tl(I) ions from aqueous solution by modified organobentonite with dithizone(D-O-bentonite) was investigated. The optimum experimental parameters for the adsorption and preconcentration of Tl(I) ions have been investigated. Moreover, the thermodynamics and kinetics of the adsorption were studied. The results showed that the Tl(I) could be quantitatively retained by the D-O-bentonite at pH 9-11. The isothermal data was described by the Langmuir equation. The dynamic data followed the pseudo-second-order kinetic model well. The enthalpy change (DH) of the adsorption process was 50.142 kJ/mol. The Gibbs free energy changes (DG) were negative, and entropy changes (DS) were positive. The activation energy (Ea) was 49.776 kJ/mol for the adsorption. The Tl(I) adsorbed on the D-O-bentonite could be completely eluated by using 0.5 mol/L nitric acid. The method has been applied to the preconcentration for flame atomic absorption spectrometric determinations of trace Tl(I) in water samples with satisfactory results.