S. Susarla et al., Adsorption and desorption characteristics of phenoxyacetic acids and chlorophenols in volcanic soil: Single component fixed bed studies, ENV TECHNOL, 20(1), 1999, pp. 1-9
Widespread application of herbicides and pesticides in recent years resulte
d in environmental contamination of soils and groundwaters. In this paper,
we examine the adsorption and desorption characteristics of three phenoxyac
etic acids and three chlorophenols in a volcanic soil using fixed bed soil
columns. A theoretical model incorporating sorption, dispersion, film trans
fer and surface diffusion in soils particles has been developed to predict
the solute movement in fixed bed soil columns. The main feature of this mod
el is that all the model parameters were obtained from independent experime
nts or from literature correlations. Experiments were carried out to examin
e the effect of concentration and flow rate on the breakthrough and elution
of phenoxyacetic acids and chlorophenols from soil columns. The results in
dicated that increasing the initial concentration and now rate resulted in
a faster breakthrough and elution of solutes. The order of breakthrough and
elution for phenoxyacetic acids was: 2,4-dichlorophenoxyacetic acid (2,4-D
) > 2-methyl, 4-chlorophenoxyacetic acid (MCPA) > 2,4,5-trichlorophenoxyace
tic acid (2,4,5-T) and while for chlorophenols the order was: 2,4-dichlorop
henol (2,4-DCP) >para-chloro-ortho-phenol (PCOC) > 2,4,5-trichlorophenol (2
,4,5-TCP). The results have also shown that the equilibrium sorption played
a dominant role in the breakthrough and elution of these chemicals from so
il columns. The results of numerical calculations using the model are compa
red with experimental results and in general, good agreement was obtained f
or all chemicals considered.