Ruan Xiuxiu, Zhu Lizhong, Chen Baoliang, Qian Guangren, Frost Ray L
School of Environmental and Chemical Engineering, Shanghai University, No. 99 Shangda Road, Shanghai 200444, China; School of Chemistry, Physics and Mechanical Engineering, Science and Engineering Faculty, Queensland University of Technology, GPO Box 2434, Brisbane, Queensland 4001, Australia.
Department of Environmental Science, Zhejiang University, Hangzhou, Zhejiang 310028, China; Ministry of Education Key Laboratory of Environmental Remediation and Ecological Health, Zhejiang University, Hangzhou, Zhejiang 310028, China.
J Colloid Interface Sci. 2015 Dec 15;460:119-27. doi: 10.1016/j.jcis.2015.08.034. Epub 2015 Aug 20.
The compound-specific mechanisms for the sorption of organic contaminants onto cetyltrimethylammonium-saturated bentonite (i.e., CTMA-Bentonite) in water were evaluated by (1)H NMR study and Linear Solvation Energy Relationship (LSER) approach. In (1)H NMR study, comparing with pure CTMAB, the up-field shifts of hydrogen peaks for CH2N(+) and CH3N(+) of CTMA(+) in CTMAB-aromatics (1-naphtylamine, aniline and phenol) mixtures are much greater than that in CTMAB-aliphatics (cyclohexanone and cyclohexanol) mixtures. Meanwhile, the peak position of hydrogen on amino- and hydroxyl-groups of aromatic compounds also changes greatly. (1)H NMR data demonstrated the strong molecular interaction between the positive ammonium group of CTMA(+) and the delocalized π-systems of aromatic solutes, whereas the interactions of CTMA(+) with aliphatic compounds having electron-donating groups (such as cyclohexanol and cyclohexanone) or aromatic ring substituted by electron-withdrawing groups (i.e., nitrobenzene) or nonpolar aromatic compounds with single phenyl ring (i.e., toluene) are weak. The derived LSER equation was obtained by a multiple regression of the solid-water sorption coefficients (Kd) of 16 probe solutes upon their solvation parameters, and demonstrates aromatics sorption onto CTMA-Bentonite is concurrently governed by the π-/n-electron pair donor-accepter interaction and the cavity/dispersion interaction, while the predominant mechanism for aliphatic compounds is the cavity/dispersion interaction, consisting with the (1)H NMR results.
