Regeneration of Exhausted Tailored Clays by Adsorbate Volatilization

Adsorption of organic pollutants with low molecular weight onto natural soils can be greatly enhanced by chemical modification referred to as tailoring of the clay fraction of the soil. Previous studies have shown that the adsorption capacity of soils for benzene and toluene are greatly increased by tailoring with quaternary amines. Regeneration studies involving volatilization of the adsorbate have been performed for three different tailored soils: Wyoming bentonite, Glendale clay-loam, and a clayish soil from the Los Angeles area. A 48% decrease from the original value of the linear adsorption constant k was observed for benzene on bentonite after six regeneration cycles. The L.A. soil showed no significant degradation in the adsorption capacity for benzene after six regeneration cycles. Also after six regeneration cycles the Glendale soil decreased its k value by 62% from the original value. The adsorption capacity of tailored bentonite for toluene was reduced by 97% after six regeneration cycles. This decaying effect does not necessarily represent a decrease in the adsorption capacity, but rather the kinetics of adsorption may play a significant role as the adsorbent becomes more granular after repeated regeneration. Adsorption studies with o-xylene showed minimal adsorption with bentonite for both virgin and regenerated soil.