Rational design of selective functionalized silica adsorbents for Hg(ii) removal from FGD wastewater. A combined experimental and theoretical study

Abstract

The binding of Hg²⁺ by mercaptan-functionalized silica possessing different physical characteristics was explored through experimental investigations and theoretical calculations. The impacts of the pore structure of silica adsorbents on functionalization and the kinetics of Hg²⁺ adsorption were also studied. The mechanism of Hg²⁺ adsorption was proposed based on the results of experimental and theoretical studies. The DFT calculations suggested a simultaneous monodentate and bidentate Hg²⁺ complex formation on sulfur-containing surface functional groups that strongly depends on the Hg²⁺ concentration. Theoretical Hg²⁺ adsorption isotherms predicted by DFT calculations have shown that even when the adsorbent surface had heterogeneous adsorption sites capable of simultaneous monodentate and bidentate complexation, the adsorption still followed the Langmuir model.