Adsorption of Hg(II) in water by thiol-functionalized MCM-41

MCM-41 was modified by 3-mercaptopropyltrimethoxysilane to remove Hg(II) from aqueous solution. The thiol-functionalized MCM-41 obtained was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). In addition, the influences of the initial solution concentration, contact time, temperature, pH and concentration of chloride ion on the adsorption ability of thiol-functionalized MCM-41 for Hg(II) in water were investigated. The results show that the adsorption of Hg(II) by thiol-functionalized MCM-41 accords with the pseudo-second-order kinetic model and the adsorption isotherm can be fitted well by the Langmuir model. The increase of temperature benefits the adsorption of Hg(II) by thiol-functionalized MCM-41, indicating that the adsorption is endothermic. The maximum adsorption capacities are 219 and 258 mg/g at the temperatures of 298 and 308 K respectively. The solution pH (2.0 to 7.6) has no significant effect on the adsorption of Hg(II) by thiol-functionalized MCM-41. However, the adsorption capacity decreases with the increase in the chloride ion concentration. Finally, the results of desorption experiments show that the thiol-functionalized MCM-41 has a relatively high affinity to Hg(II).