title: Removal of 2,4,6-trichlorophenol from a solution by humic acids repeatedly extracted from a peat soil.
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 (13)C 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 (K(oc)) was weakly correlated with the chemical compositions of HAs. However, a positive trend between K(oc) 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.
authors: Department of Soil & Environmental Sciences, National Chung Hsing University, Taichung 40227, Taiwan. ymtzou@dragon.nchu.edu.tw
authors: Yu-Min
authors: YM
authors: Tzou
authors: Shan-Li
authors: SL
authors: Wang
authors: Jen-Chyi
authors: JC
authors: Liu
authors: Ying-Ying
authors: YY
authors: Huang
authors: Jen-Hshuan
authors: JH
authors: Chen
mesh_terms: D000327:Adsorption; D002733:Chlorophenols / Q000302:isolation & purification*; D006812:Humic Substances; D012989:Soil Pollutants / Q000302:isolation & purification*
chemical_list: D002733:Chlorophenols; D006812:Humic Substances; D012989:Soil Pollutants; C024564:2,4,6-trichlorophenol