Affiliations: Department of Environmental Science, Zhejiang
University, Hangzhou 310028, China | Environmental Science Research & Design Institute
of Zhejiang Province, Hangzhou 310007, China
Abstract: Organobentonites synthesized by replacing the metal ions in
bentonite with cetyltrimethylammonium (CTMA) or tetramethylammonium cation
(TMA) were investigated for their behaviors to sorb benzene, toluene, p-xylene
from water. The results served to distinguish the sorption mechanisms
(adsorption or partition) of the two types of organobentonites. Bentonites
modified with short-chain alkyl functional groups (e. g., TMA) sorb organic
contaminants primarily by an adsorption process, in which the sorbed amount
decreases with increasing steric hindrance of the organic compound and the
process exhibits a competitive effect because of steric hindrance in
multi-solute systems. In contrast, the sorption of contaminants to
organobentonites modified with long-chain alkyl groups (e. g., CTMA) occurs by
partition process without exhibiting a competitive effect, and the additional
organic compounds may induce a cosorptive effect. In the latter case, the
measured distribution coefficients of organic compounds between
organobentonites and water (log K_d) are positively
correlated with the octanol-water partition coefficients of the compounds
(logK_{ow}) and the sorption process exhibits no competitive
effect in multi-solutesystems.
