The mechanism of Zn sup 2+ adsorption on calcite

Journal Article · Thu Sep 01 00:00:00 EDT 1988 · Geochimica et Cosmochimica Acta; (USA)

DOI:https://doi.org/10.1016/0016-7037(88)90130-5· OSTI ID:5221370

Zachara, J M ^[1]; Kittrick, J A; Harsh, J B ^[2]

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1. Pacific Northwest Laboratory, Richland, WA (USA)
2. Washington State Univ., Pullman, WA (USA)

The adsorption of Zn{sup 2+} on calcite (CaCO{sub 3(s)}) was investigated from aqueous solutions in equilibrium with CaCO{sub 3(s)} and undersaturated with respect to Zn{sub 5}(OH){sub 6}(CO{sub 3}){sub 2(s)}. Zinc adsorption occurred via exchange with Ca{sub 2+} in a surface-adsorbed layer on calcite. The validity of this exchange reaction was supported by adsorption isotherm and constant concentration experiments, where Ca{sup 2+}{sub aq} was varied by systematically changing the pH and CO{sub 2(g)}. Greater adsorption of Zn{sup 2+} occurred at higher pH and Co{sub 2(g)} levels, where Ca{sup 2+} activities were lowest. Sites available for Zn{sup 2+} sorption were less than 10% of Ca{sup 2+} sites on the calcite surface. Surface exchange of Zn{sup 2+} did not affect the solubility of calcite. Zinc sorption was apparently independent of surface charge, which suggested that the surface complex had covalent character. Desorption and isotopic exchange experiments indicated that the surface complex remained hydrated and labile as Zn{sup 2+} was rapidly exchangeable with Ca{sup 2+}. Careful analysis of the adsorption data showed that Zn{sup 2+} and ZnOH{sup +} were the sorbing species.

• OSTI ID: 5221370
• Journal Information: Geochimica et Cosmochimica Acta; (USA), Journal Name: Geochimica et Cosmochimica Acta; (USA) Vol. 52:9; ISSN GCACA; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
ADSORPTION
ALKALINE EARTH METAL COMPOUNDS
CALCITE
CALCIUM CARBONATES
CALCIUM COMPOUNDS
CARBON COMPOUNDS
CARBONATE MINERALS
CARBONATES
CHARGED PARTICLES
CHEMISTRY
DISPERSIONS
EQUILIBRIUM
GEOCHEMISTRY
ION EXCHANGE
IONS
MINERALS
MIXTURES
OXYGEN COMPOUNDS
PH VALUE
SOLUTIONS
SORPTION
SORPTIVE PROPERTIES
SURFACE PROPERTIES
ZINC IONS