PREPARATION, CHARACTERIZATION AND APPLICATIONS AS HEAVY-METALS SORBENTS OF COVALENTLY GRAFTED THIOL FUNCTIONALITIES ON THE INTERLAMELLAR SURFACE OF MONTMORILLONITE

A novel type of heavy metal adsorbent was prepared by the covalent grafting of a chelating sulfhydryl functionality [(3-mercaptopropyl)trimethoxysilane) in the interlamellar region of the smectite clay mineral montmorillonite. The new material (designated as thiomont) was characterized by X-ray diffraction, infrared spectroscopy, thermogravimetric analysis, X-ray fluorescence, and C-13 solid-state NMR spectroscopy. Its approximate chemical formula was deduced to be Si7.8Al3.3Fe0.3Mg0.4O(16)(OH)(3)[OSi(OH)(2)(CH2)(3)SH](5). Thiomont was found to be an effective adsorbent for Pb(II) and Hg(II) (70 and 65 mg of metal/g of adsorbent, respectively) but was less effective toward Cd(II) and Zn(II). Acid leaching was shown to be an effective method by which thiomont could be regenerated.