Adsorption of Chlorinated Phenols from Aqueous Solution by Surfactant-Modified Pillared Clays

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Abstract
New pillared clay-based adsorbents have been prepared by incorporating a nonionic surfactant of general formula C~z_~4H25_290(CH2CHzO)sH (commercial name, Tergitol 15S-5), during the synthesis of the aluminum hydroxide pillaring reagent. Different loadings of surfactant have been examined. The presence of the surfactant enhanced the adsorption capacity of the clay toward 3-monochlorophenol from aqueous solution. On the basis of adsorption results for a series of clays with increasing surfactant loadings, the best adsorbent was obtained at a surfactant loading of 255 mg/g of clay. At this loading, the surfactant occupies the micropores, as well as the mesopores and the external surfaces of the pillared clay. Analysis of the adsorption isotherms for 3-monochlorophenol, 3,5-dichlorophenol, 3,4,5-trichlorophenol and pen- tachlorophenol at different pH shows that the most energetic adsorption sites are the surfactant-occupied micropores between pillars. Additional binding of chlorinated phenols occurs at surfactant sites on external surfaces and mesopores. Upon calcination at 500~ the clay is converted to a conventional alumina- pillared clay with a basal spacing near 16 A. This calcined product can be reused as an adsorbent for chlorinated phenols by readsorbing fresh surfactant. The recycled adsorbent exhibits performance prop- erties comparable to the original adsorbent. These results demonstrate the feasibility of utilizing a sur- factant-modified pillared clay as a recyclable adsorbent and combustion catalyst for environmental pol- lutants.

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