Competitive Adsorption of Xylene and Toluene on Modified and Unmodified Sodium Bentonite Clay Mineral

Abstract

Cetyltrimethylammonium bromide (CTAB) – modified and unmodified sodium bentonite were both used for the competitive adsorption of m-xylene and toluene from their aqueous solution. Infrared spectroscopy (IR) and expansion tests (adsorption capacity and Foster swelling) measurement were performed in order to evaluate the performance of the adsorbents. The FT-IR results indicated that the quaternary ammonium salts (CTAB) were intercalated between the layers of the sodium bentonite clay. The Foster swelling test results indicated that the affinity of CTAB was more in the treated clay for all other organic compounds tested. The result showed that modified sodium bentonite swelled more than the unmodified and the order of the swelling factor is; m- xylene > toluene > gasoline > diesel > kerosene > water. However, when the assay was performed under agitation, it yielded higher swelling capacity. The modified clay exhibited very high capacity of adsorption compare to unmodified samples. The m-xylene and toluene uptake follows a pseudo second order kinetics mechanism, suggesting that the rate determining step of adsorption involves the two adsorbates competitively adsorbed on the adsorbent sites. Therefore this organo-modified bentonite can be used for the removal of organics from polluted aqueous effluents.