title: X-ray absorption near edge structure study of lead sorption on phosphate-treated kaolinite.
abstract: Presorbed phosphate significantly increases Pb sorption on the phyllosilicate kaolinite in the pH range from 4to 8. The sorbed Pb-to-P molar ratios over this pH range stray little from the molar ratio found in the mineral pyromorphite, suggesting sorbed phosphate reacts with soluble Pb to form a surface precipitate similar to pyromorphite. X-ray absorption near edge structure (XANES) studies at the Pb L3-edge support this interpretation. In particular, the fine structure of first-derivative Pb L3-edge XANES spectra of Pb species sorbed to phosphate-treated kaolinite samples covering a pH range extending from 4 to 10 match the fine structure of the spectrum of pyromorphite. Although the productis structurally and compositionally similarto pyromorphite, the ion activity product in the pH range 4-6 was undersaturated with respect to the solubility product of pyromorphite.
authors.affiliation: Department of Natural Resources and Environmental Sciences, P.O. Box 1208, Alabama A&M University, Normal, Alabama 35762, USA.
authors.forename: Robert W
authors.initials: RW
authors.lastname: Taylor
authors.forename: William F
authors.initials: WF
authors.lastname: Bleam
authors.forename: Thilini D
authors.initials: TD
authors.lastname: Ranatunga
authors.forename: Cristian P
authors.initials: CP
authors.lastname: Schulthess
authors.forename: Zachary N
authors.initials: ZN
authors.lastname: Senwo
authors.forename: Don Rufus A
authors.initials: DR
authors.lastname: Ranatunga
mesh_terms: D007616:Kaolin; D007854:Lead / Q000737:chemistry*; D010710:Phosphates / Q000737:chemistry*; D013057:Spectrum Analysis / Q000379:methods*; D014965:X-Rays
chemical_list: D010710:Phosphates; D007616:Kaolin; D007854:Lead