In order to develop highly efficient and low-cost treatment technique for heavy metal wastewater and promote the resource utilization of sepiolite, natural sepiolite was modified by using thioglycollic acid and characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), specific surface, Zeta potential and infrared spectrum (IR) analysis, and the adsorption kinetic and thermodynamic characteristics of the modified sepiolite to Hg(Ⅱ) in water were studied by static adsorption experiments. The results showed that sulfydryl groups were grafted onto sepiolite, and the surface of the modified sepiolite became smoother with more gaps and negative charges to improve the adsorption ability for Hg(Ⅱ). The optimal pH for Hg(Ⅱ) adsorption on the modified sepiolite was 6, and the adsorption process reached equilibrium in 60 min at 30℃. This process could be described by the pseudo second-order kinetic equation, and the initial adsorption rate constant was 0.063 mg·(g·min)-1. The adsorption thermodynamic characteristics could be well described by Langmuir isothermal adsorption model, and the maximum adsorption capacity was 3.256 mg·g-1. The investigation revealed that the adsorption process was a spontaneous endothermic process, resulting in physical adsorption and chemical adsorption, which was dominated by physical adsorption.
Keywords: adsorption kinetics; adsorption thermodynamics; mercury; sepiolite; sulfydryl modification.