Mg. Stapleton et al., SORPTION OF PENTACHLORPHENOL TO HDTMA-CLAY AS A FUNCTION OF IONIC-STRENGTH AND PH, Environmental science & technology, 28(13), 1994, pp. 2330-2335
We investigated the sorption of pentachlorophenol (PCP) to a surfactan
t-modified clay and the solubility of PCP as a function of pH and ioni
c strength. Pentachlorophenol is a hydrophobic ionizable organic compo
und; therefore, it can exist as either a protonated or a deprotonated
species. The objectives of this study were to determine differences in
the sorption and solubility of the two species and to model the sorpt
ion as a function of pH. We developed a model that described the sorpt
ion across the experimental pH range (4-8.5). The model represented th
e sorption of the deprotonated species by a Langmuir-type isotherm and
the sorption of the protonated species by a linear isotherm. Between
pH 4 and pH 8.5, the sorption decreases by three times and the solubil
ity increases by 3 orders of magnitude as the dominant aqueous species
changes from the protonated to the deprotonated form.