Removal of 2,4,6-trichlorophenol from a solution by humic acids repeatedly extracted from a peat soil
Journal
Journal of Hazardous Materials
Journal Volume
152
Journal Volume
152
Journal Issue
2
Journal Issue
2
Pages
812-819
Start Page
812
End Page
819
ISSN
03043894
Date Issued
2008-08-01
Author(s)
Abstract
Humic acid (HA) is one of the major components of soil organic matter. It strongly affects the sorption behavior of organic and inorganic contaminants in soils. To obtain a better understanding of the interactions of contaminants with HA, a repeated extraction technique has been applied to a peat soil to obtain HA fractions with varying aliphaticity and aromaticity, which were subsequently correlated to the sorption properties of 2,4,6-trichlorophenol (TCP). HA fractions were extracted repeatedly using an alkaline solution and each HA fraction was separated into two portions with an air-drying or re-suspending (denoted as RSHAs) process. Solid-state 13C NMR and elemental analysis demonstrated that the aromaticity and polarity of HAs decreased with extractions. Kinetic results indicated that air-dried HAs exhibited two-step first order sorption behavior with a rapid stage followed by a slower stage. The slower sorption is attributed to the diffusion of 2,4,6-TCP in the condensed aromatic domains of HAs. Conversely, sorption of 2,4,6-TCP on RSHAs was extremely rapid and could not be fitted with any kinetic model. For air-dried HAs the sorption capacity (Koc) was weakly correlated with the chemical compositions of HAs. However, a positive trend between Koc and aromaticity was observed for RSHAs. Compared with the results of air-dried HAs with their counterparts of RSHAs, it is therefore concluded that air-drying may alter the structure of HAs through artificially creating a more condensed domain in HAs. The structural alternation may result in an incorrect interpretation of the relationship between sorption capacity and chemical composition of HAs and a misjudgment of the transport behavior of 2,4,6-TCP in soils and sediments.
Subjects
2
4
6-Trichlorophenol
Aliphaticity
Aromaticity
Linear sorption
Nonlinear sorption
Sorption isotherm
Type
journal article