Abiotic association of phthalic acid esters with humic acid of a sludge landfill

Abstract

The abiotic association between phthalic acid esters (PAEs) and humic substances (HS) in sludge landfill plays an important role in the fate and stability of PAEs. An equilibrium dialysis combined with ¹⁴C-labeling was used to study the abiotic association of two abundant PAEs (diethyl phthalate and di-n-butyl phthalate) with humic acid (HA) isolated from a sludge landfill with different stabilization times and different molecular weights. Elemental analysis and Fourier Transform Infrared Spectrophotometer (FTIR) suggested that high K_A value of HA was related to the high aromatic content and large molecular weight of HA. The results indicated that the association strength of PAEs with HA depended on both the properties of the PAEs and the characteristics of HA. The K_A values of the association were strongly dependent on solution pH, and decreased dramatically as the pH was increased from 3.0 to 9.0. The results suggested that non-specific hydrophobic interaction between PAEs and HA was the main contributor to the association of the PAEs with HA. The interactive hydrogen-bonds between the HA and the PAEs molecules may also be involved in the association.

Keywords

abiotic association / phthalic acid esters (PAEs) / humic acid / sludge / landfill

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Acknowledgements

This work was supported by the National Natural Science Foundation of China (Grant Nos. 20877057, 51078285 ).

The authors declare that no competing financial conflicts exist.

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2014 Higher Education Press and Springer-Verlag Berlin Heidelberg