Adsorption of chlorinated compounds (chLorobenzene, chLoroform, and carbon tetrachloride) on microporous SiO2, Ag-doped SiO2 and natural and dealuminated clinoptilolites

Abstract

Adsorption isotherms of chLoroorganic compounds on natural and dealuminated clinoptilolite zeolites, as well as on pure and Ag-doped microporous SiO2, were measured by a gas chromatography technique. The SiO2 microporous solids were synthesized by the sol-gel method from tetraethoxysilane and in the presence of methanol. Dealuminated clinoptilolite zeolites were obtained by means of HCl treatment of a natural precursor. Adsorption of chlorinated compounds (CxHyClz), such as chLorobenzene, chLoroform, and carbon tetrachloride, on SiO2, Ag-doped SiO2 and on the clinoptilolite zeolites was studied in the temperature range of 398-498 K. The Freundlich and Dubinin-Astakhov adsorption equations approximately fitted the CxHyClz adsorption data, within the selected temperature range. The energies of interaction between chlorinated adsorbates and microporous SiO2, Ag-doped SiO2, and clinoptilolite substrates were evaluated from the isosteric heats of adsorption (q(st)), which were found to obey the following decreasing order: q(st) (chLorobenzene) > q(st) (chLoroform) > q(st) (carbon tetrachloride).