title: Zn Isotope Fractionation during Sorption onto Kaolinite.
abstract: In this study, we quantify zinc isotope fractionation during its sorption onto kaolinite, by performing experiments under various pH, ionic strength, and total Zn concentrations. A systematic enrichment in heavy Zn isotopes on the surface of kaolinite was measured, with Δ(66)Znadsorbed-solution ranging from 0.11‰ at low pH and low ionic strength to 0.49‰ at high pH and high ionic strength. Both the measured Zn concentration and its isotopic ratio are correctly described using a thermodynamic sorption model that considers two binding sites: external basal surfaces and edge sites. Based on this modeling approach, two distinct Zn isotopic fractionation factors were calculated: Δ(66)Znadsorbed-solution = 0.18 ± 0.06‰ for ion exchange onto basal sites, and Δ(66)Znadsorbed-solution = 0.49 ± 0.06‰ for specific complexation onto edge sites. These two distinct factors indicate that Zn isotope fractionation is dominantly controlled by the chemical composition of the solution (pH, ionic strength).
authors.affiliation: Institut De Physique Du Globe De Paris-Sorbonne Paris Cite, Universite Paris Diderot , CNRS UMR 7154, Paris, France.
authors.forename: Damien
authors.initials: D
authors.lastname: Guinoiseau
authors.affiliation: Institut De Physique Du Globe De Paris-Sorbonne Paris Cite, Universite Paris Diderot , CNRS UMR 7154, Paris, France.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Gélabert
authors.affiliation: Institut De Physique Du Globe De Paris-Sorbonne Paris Cite, Universite Paris Diderot , CNRS UMR 7154, Paris, France.
authors.forename: Julien
authors.initials: J
authors.lastname: Moureau
authors.affiliation: Institut De Physique Du Globe De Paris-Sorbonne Paris Cite, Universite Paris Diderot , CNRS UMR 7154, Paris, France.
authors.forename: Pascale
authors.initials: P
authors.lastname: Louvat
authors.affiliation: Institut De Physique Du Globe De Paris-Sorbonne Paris Cite, Universite Paris Diderot , CNRS UMR 7154, Paris, France.
authors.forename: Marc F
authors.initials: MF
authors.lastname: Benedetti
mesh_terms: D000327:Adsorption; D005591:Chemical Fractionation; D007616:Kaolin / Q000737:chemistry*; D012989:Soil Pollutants / Q000737:chemistry*; D015032:Zinc / Q000737:chemistry*; D015033:Zinc Isotopes / Q000737:chemistry
chemical_list: D012989:Soil Pollutants; D015033:Zinc Isotopes; D007616:Kaolin; D015032:Zinc