Influences of preparative methods of humic acids on the sorption of 2,4,6-trichlorophenol
Journal
Chemosphere
Journal Volume
70
Journal Volume
70
Journal Issue
7
Journal Issue
7
Pages
1218-1227
Start Page
1218
End Page
1227
ISSN
00456535
Date Issued
2008-01
Author(s)
Abstract
Humic acids (HAs) are a major component of soil organic matter which strongly affects the sorption behavior of organic contaminants in soils. To assess the sorption-desorption characteristics of organic compounds on HAs, the organic adsorbent is usually isolated using an acid-base extraction method followed by air-drying or freeze-drying. In this study, a peat soil from the Yangming mountain area of Taiwan was sampled and repeatedly extracted followed by either air-drying or a non-drying treatment (denoted DHAs and NDHAs, respectively). The sorption of 2,4,6-TCP on HAs was evaluated using the batch method. Kinetic sorption results indicated that DHAs exhibited a two-step first-order sorption behavior, involving a rapid sorption followed by a slow sorption. The slow sorption may be attributed to the diffusion of 2,4,6-TCP through the condensed aromatic domains of HAs. On the contrary, the sorption of 2,4,6-TCP on NDHAs was extremely rapid, and the sorption data did not fit existing kinetic models. Each HA sample exhibited a nonlinear sorption isotherm. Sorption nonlinearity (represented by Freundlich N values) and Koc had a positive relationship with aliphaticity for DHAs; however, nonlinearity and Koc correlated positively with aromaticity when NDHAs adsorbents were used. We conclude that the air-drying technique may artificially create a more condensed area, which strongly affects the sorption characteristics of HAs. Thus, an incorrect evaluation of the sorption capacity and its relationship with the chemical composition of HAs would arise following use of the air-drying method.
Subjects
2
4
6-Trichlorophenol
Aliphaticity
Aromaticity
Nonlinear sorption isotherm
Type
journal article