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Pesticide sorption and desorption by lignin described by an intraparticle diffusion model

van Beinum, W., Beulke, S. and Brown, C.D. (2005) Pesticide sorption and desorption by lignin described by an intraparticle diffusion model. Environmental Science and Technology, 40 (2). pp. 494-500. ISSN 1064-3389

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Lignin was used as a model compound for soil organic matter to gain insight into the mechanisms that control the kinetics of pesticide sorption and desorption. Hydrolytic lignin was immobilized in a matrix of alginate gel, and sorption−desorption experiments were undertaken with isoproturon. Sorption increased with time and was close to equilibrium after 14 days. Desorption was measured after sorption for different time intervals and for a number of successive desorption steps of different lengths. The results showed strong differences between the sorption and desorption isotherms. The ratio of sorbed to dissolved pesticide approached and even exceeded the equilibrium ratio, depending on the number of desorption steps and the length of each equilibration period. A numerical diffusion model was developed to describe radial diffusion into the lignin particles in combination with Freundlich sorption inside the particles. Key model parameters were adjusted to fit the sorption data, and the same parameters were then used to predict stepwise desorption. Desorption was well described by the model, which suggests that sorption and desorption were driven by the same mechanism and occurred at the same rate. The observed difference between the sorption and desorption isotherms could be fully explained by the nonattainment of equilibrium due to slow diffusion into and out of the lignin particles.

Item Type: Article
Institution: The University of York
Academic Units: The University of York > Environment (York)
Depositing User: York RAE Import
Date Deposited: 29 May 2009 14:19
Last Modified: 29 May 2009 14:19
Published Version: http://dx.doi.org/10.1021/es051940s
Status: Published
Publisher: Taylor & Francis
Identification Number: 10.1021/es051940s
URI: http://eprints.whiterose.ac.uk/id/eprint/6069

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