Assessment of the Sorptive Fractionation of Organic Matter at the Goethite-Water Interface
2025
Tesfa, Marawit | Dia, Aline | Hanna, Khalil | Cheng, Wei | Pédrot, Mathieu | Marsac, Rémi | Géosciences Rennes (GR) ; Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des sciences de l'environnement de Rennes (OSERen) ; Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE) | Institut des Sciences Chimiques de Rennes (ISCR) ; Université de Rennes (UR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes) ; Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Ecole Nationale Supérieure de Chimie de Rennes (ENSCR)-Institut de Chimie - CNRS Chimie (INC-CNRS)-Centre National de la Recherche Scientifique (CNRS) | South-Central MinZu University (SCUEC) | Institut de Physique du Globe de Paris (IPG Paris) | GeOHeLiS | ANR-18-CE01-0008,C-FACTOR,Le devenir des contaminants est contrôlé par la spéciation de la matière organique colloïdale(2018)
International audience
Show more [+] Less [-]English. The carboxylic (COOH) and phenolic (PhOH) functional groups of natural organic matter (NOM) are the major binding sites for environmental compounds such as minerals and contaminants. This study focusses on the sorptive fractionation of a humic acid onto goethite (α-FeOOH) at various pH, [NOM], [NaCl], and under static (batch) and dynamic flow (column) conditions. During batch experiments at low pH and [NOM], adsorption behaviors of COOH- and PhOH-rich compounds were similar. At low [NaCl] and high pH or [NOM], the adsorption of NOM decreased, with a preferential adsorption of PhOH over COOH-rich compounds. This can be ascribed to the surface site saturation and competition between COOH, PhOH and OH- for surface binding, combined with electrostatic effects. Higher [NaCl], which was previously shown to favor NOM-NOM interactions at mineral surface, led to increased adsorption of COOH, while the adsorption of PhOH was not affected. Under flow-through conditions, multiple-binding-site mechanism was shown to control the fractionation of PhOH- and COOH-rich compounds. These results provide insights into the molecular interactions between the NOM and soil components, which control the fate and behavior of contaminants and nutrients in the environment.
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