Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Record number 536385
Title Proton and Copper Binding to Humic Acids Analyzed by XAFS Spectroscopy and Isothermal Titration Calorimetry
Author(s) Xu, Jinling; Koopal, Luuk K.; Fang, Linchuan; Xiong, Juan; Tan, Wenfeng
Source Environmental Science and Technology 52 (2018)7. - ISSN 0013-936X - p. 4099 - 4107.
Department(s) Physical Chemistry and Soft Matter
Publication type Refereed Article in a scientific journal
Publication year 2018
Abstract Proton and copper (Cu) binding to soil and lignite-based humic acid (HA) was investigated by combining X-ray absorption fine structure (XAFS) spectroscopy, isothermal titration calorimetry (ITC), and nonideal-competitive-adsorption (NICA) modeling. NICA model calculations and XAFS results showed that bidentate and monodentate complexation occurred for Cu binding to HA. The site-type-specific thermodynamic parameters obtained by combining ITC measurements and NICA calculations revealed that copper binding to deprotonated carboxylic-type sites was entropically driven and that to deprotonated phenolic-type sites was driven by entropy and enthalpy. Copper binding to HA largely depended on the site-type and coordination environment, but the thermodynamic binding mechanisms for Cu binding to the specific site-types were similar for the different HAs studied. By comparing the site-type-specific thermodynamic parameters of HA-Cu complexation with those of low molar mass organic acids, the Cu coordination could be further specified. Bidentate carboxylic-Cu complexes made the dominating contributions to Cu binding to HA. The present study not only yields molecular-scale mechanisms of ion binding to carboxylic- and phenolic-type sites of HA but also provides the new insight that the universal nature of site-type-specific thermodynamic data enables quantitative estimation of the binding structures of heavy metal ions to humic substances.
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