Ht. Zhao et al., SORPTION OF THE IONIZABLE ORGANIC-COMPOUND, DICAMBA (3,6-DICHLORO-2-METHOXY BENZOIC-ACID), BY ORGANO-CLAYS, Chemosphere, 33(10), 1996, pp. 2089-2100
The sorption of 3,6-dichloro-2-methoxy benzoic acid (dicamba) by hexad
ecyltrimethylammonium (HDTMA) and dioctadecyldimethylammonium (DODMA)
exchanged smectites was studied at different concentrations and pH lev
els to evaluate the capability of organo-clays to sorb an ionizable hy
drophobic compound. Dicamba-organo-clay complexes were also prepared a
nd characterized by X-ray diffraction (XRD) and Fourier transform infr
ared spectroscopy (FT-IR). Results indicated that organo-clays were ef
fective sorbents for dicamba, a water-soluble, ionizable, and potentia
lly mobile organic compound. Organo-clays with higher organic carbon c
ontents usually resulted in greater dicamba sorption. Solution pH sign
ificantly affected the sorption of dicamba by organo-clays, with the i
sotherm inflection point near the dicamba pK(a) value. Nearly twice as
much dicamba could be sorbed in the molecular form as compared to its
anionic, deprotonated form. Excessive DODMA contributed to dicamba so
rption at pH levels greater than its pK(a). Hydrophobic interactions a
nd ionic attractions were responsible for the retention of dicamba by
organo-clays. Copyright (C) 1996 Elsevier Science Ltd