Study of Hg(II) species removal from aqueous solution using hybrid ZnCl2-MCM-41 adsorbent

A novel ZnCl2-MCM-41 adsorbent was prepared by method of solvent dispersion in toluene and characterized using XRD, N2 adsorption–desorption, FTIR and TGA techniques. The synthesized ZnCl2-MCM-41 sorbent possessed high specific surface area (602.3 m2 g−1), narrow pore size distribution (2.37 nm) and total pore volume (0.46 cm3 g−1). The hybrid sorbent was applied for the removal of Hg(II) from aqueous solution under different experimental conditions by varying contact time, initial concentration of Hg(II), pH, presence of interfering ions and solution temperature. It was found that amount of Hg(II) sorption increased with enhancement of Hg(II) initial concentration, contact time and pH but decreased as the temperature increased. Optimum conditions obtained were 20 °C, pH 10 and contact time of 30 min. Effects of foreign anions and cations on Hg(II) removal were studied and it was found that chloride ion affected strongly on adsorption. For experimental data the Langmuir isotherm showed a better fit and maximum adsorption capacity was obtained 204.1 mg g−1 for an initial concentration range 2–50 mg L−1. From the D–R isotherm, the mean free energy was calculated as 9.128 kJ mol−1 indicating that the sorption of Hg(II) was taken place by chemical reaction.