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Distribution Behavior of Pyrene to Adsorbed Humic Acids on Kaolin
Author(s) -
Terashima Motoki,
Tanaka Shunitz,
Fukushima Masami
Publication year - 2003
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2003.5910
Subject(s) - pyrene , adsorption , chemistry , humic acid , partition coefficient , aqueous solution , benzo(a)pyrene , quenching (fluorescence) , chromatography , fluorescence , organic chemistry , fertilizer , physics , quantum mechanics
The distribution behavior of pyrene on humic acid (HA)–kaolin complexes, prepared by adsorbing HA on kaolin, was investigated by batch experiments. The distribution coefficient ( K d ) of pyrene on the HA–kaolin complex increased with the fraction ( f oc ) of organic carbon adsorbed to the surface of the kaolin. This can be attributed to hydrophobic interactions between pyrene and the adsorbed HAs. The effects of adsorbed HAs were quantitatively evaluated by calculating the distribution coefficient ( K oc ) and affinity constant ( K ads oc ) for pyrene to the adsorbed HAs. A fluorescence quenching method was employed to determine the affinity constant ( K aq oc ) of pyrene to HAs dissolved in an aqueous solution. When the K oc values were compared with the K aq oc values, the K oc values were found to be 4 to 11 times larger than the K aq oc values. On the other hand, the K ads oc values were 4 to 9 times larger than the K aq oc values. These indicate that the affinity for pyrene is enhanced by the adsorption of HAs to kaolin. In addition, the K oc values increased with increasing average molecular weights of the HAs. These results demonstrate that HAs, when they are adsorbed to clay minerals, play an important role in the deposition of polycyclic aromatic hydrocarbons (PAHs) in a soil environment.