title: Influence of Zn(II) on the adsorption of arsenate onto ferrihydrite.
abstract: Addition of iron oxide to arsenic-contaminated soil has been proposed as a means of reducing the mobility of arsenic in the soil. Arsenic and zinc are common coexisting contaminants in soils. The presence of zinc therefore may affect the adsorption properties of arsenic on iron oxide, and may thus affect its mobility in the soil. The influence of Zn(II) on the adsorption of arsenate ions on iron oxide was studied. Batch adsorption experiments indicated that Zn(II) increased the arsenate removal from a solution by ferrihydrite at pH 8. However, ATR-FTIR spectroscopy showed that no adsorption of arsenate on a ferrihydrite film occurred at pD 8 in the presence of Zn(II). Precipitation of zinc hydroxide carbonate followed by arsenate adorption onto the precipitate was found to be a plausible mechanism explaining the arsenate removal from a solution in the presence of Zn(II) at pH/pD 8. The previously suggested mechanisms attributing the enhanced removal of arsenate from solution in the presence of Zn(II) to additional adsorption on iron oxides could not be verified under the experimental conditions studied. It was also shown that at pH/pD 4, the presence of Zn(II) in the system did not significantly affect the adsorption of arsenate on ferrihydrite.
authors.affiliation: Chemical Technology, Luleå University of Technology, SE-97187 Luleå, Sweden. ivacar@ltu.se
authors.forename: Ivan
authors.initials: I
authors.lastname: Carabante
authors.forename: Mattias
authors.initials: M
authors.lastname: Grahn
authors.forename: Allan
authors.initials: A
authors.lastname: Holmgren
authors.forename: Jurate
authors.initials: J
authors.lastname: Kumpiene
authors.forename: Jonas
authors.initials: J
authors.lastname: Hedlund
mesh_terms: D000327:Adsorption; D001149:Arsenates / Q000302:isolation & purification*; D002254:Carbonates / Q000737:chemistry; D011232:Chemical Precipitation; D005290:Ferric Compounds / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D006878:Hydroxides / Q000737:chemistry; D008855:Microscopy, Electron, Scanning; D012996:Solutions; D017550:Spectroscopy, Fourier Transform Infrared; D014961:X-Ray Diffraction; D015032:Zinc / Q000737:chemistry*; D017967:Zinc Compounds / Q000737:chemistry
chemical_list: D001149:Arsenates; D002254:Carbonates; D005290:Ferric Compounds; D006878:Hydroxides; D012996:Solutions; D017967:Zinc Compounds; C092844:ferric oxyhydroxide; C036650:zinc carbonate; D015032:Zinc; C025657:arsenic acid; C052745:zinc hydroxide