title: A model-based evaluation of sorptive reactivities of hydrous ferric oxide and hematite for U(VI).
abstract: The sorption of uranyl onto hydrous ferric oxide (HFO) or hematite was measured by discontinuously titrating the suspensions with uranyl at pH 5.9, 6.8, and 7.8 under Pco2 = 10(-35)atm (sorption isotherms). Batch reactors were used with equilibration times up to 48 days. Sorption of 1 microM uranyl onto HFO was also measured versus pH (sorption edge). A diffuse double layer surface complexation model was calibrated by invoking three sorption species that were consistent with spectroscopic evidence for predominance of bidentate complexes at neutral pH and uranyl-carbonato complexes: > SOH:UO2OH(+1), (> SO)2: UO2CO3(-2), and (> SO)2:(UO2)3(OH)5(-1). The model was consistent with previously published isotherm and edge data. The model successfully predicted sorption data onto hematite, only adjusting for different measured specific surface area. Success in application of the model to hematite indicates that the hydrated surface of hematite has similar sorptive reactivity as HFO.
authors.affiliation: Environmental Engineering, The Pennsylvania State University, 212 Sackett building, University Park, Pennsylvania 16802, USA. jhjang2004@gmail.com
authors.forename: Je-Hun
authors.initials: JH
authors.lastname: Jang
authors.forename: Brian A
authors.initials: BA
authors.lastname: Dempsey
authors.forename: William D
authors.initials: WD
authors.lastname: Burgos
mesh_terms: D000327:Adsorption; D002138:Calibration; D052918:Environmental Restoration and Remediation; D005290:Ferric Compounds / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008956:Models, Chemical; D014501:Uranium / Q000737:chemistry*
chemical_list: D005290:Ferric Compounds; C000499:ferric oxide; D014501:Uranium