Geoscience Reference
In-Depth Information
Fig. 8.20 Solubilization rate
of trichloroethylene as
affected by surfactant type
and concentration; Cs and
C denote surfactant
concentration and initial
surfactant concentration,
respectively. Reprinted from
Zhong et al. (
2003
).
Copyright 2003 with
permission of Elsevier
by Khachikian and Harmon (
2000
). Here, we discuss selected examples to illus-
trate this phenomenon.
Zhong et al. (
2003
) studied the apparent solubility of trichloroethylene in
aqueous solutions, where the experimental variables were surfactant type and
cosolvent concentration. The surfactants used in the experiment were sodium
dihexyl sulfosuccinate (MA-80), SDS, polyoxyethylene 20 (POE 20), sorbitan
monooleate (Tween 80), and a mixture of Surfonic PE-2597 and Witconol
NP-100. Isopropanol was used as the alcohol cosolvent. Figure
8.20
shows the
results of a batch experiment studying the effects of type and concentration of
surfactant on solubilization of trichloroethylene in aqueous solutions. A correlation
between surfactant chain length and solubilization rate may explain this behavior.
However, the solubilization rate constants decrease with surfactant concentration.
Addition of the cosolvent isopropanol to MA-80 increased the solubility of iso-
propanol at each surfactant concentration but did not demonstrate any particular
trend in solubilization rate of isopropanol for the other surfactants tested. In the
case of anionic surfactants (MA-80 and SDS), the solubility and solubilization rate
increase with increasing electrolyte concentration for all surfactant concentrations.
Speciation of transition metals by ''natural'' organic substances that behave as
complexing ligands may occur in the subsurface following waste and sludge
disposal. As a result, metal solubility increases, favoring metal mobility with
depth. Haitzer et al. (
2002
) report binding of mercury(II) to DOM as a function of
the Hg-DOM concentration ratio. Humic and fulvic acids, which were isolated
from water originating from a site in the Florida Everglades, were used as DOM
binding material. Comparing the Hg binding capacity of natural DOM to a chelate
(ethylenediamine tetraacetic acid, EDTA), the natural DOM ligand was observed
