Solution ion effects on the surface exchange of selenite on calcite

Journal Article · Wed Aug 01 00:00:00 EDT 1990 · Geochimica et Cosmochimica Acta; (USA)

DOI:https://doi.org/10.1016/0016-7037(90)90047-O· OSTI ID:6142461

Cowan, C E; Zachara, J M; Resch, C T ^[1]

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1. Battelle Pacific Northwest Laboratories, Richland, WA (USA)

The adsorption of SeO{sub 3} on CaCO{sub 3}(s) was evaluated in equilibrium CaCO{sub 3}(aq) suspensions over a range in pH and SeO{sub 3} concentration in the absence and presence of the cosolutes, Mg, SO{sub 4}, and PO{sub 4}. Selenite was adsorbed by CaCO{sub 3}(s) in a manner consistent with its exchange on anionic specific surface sites saturated with CO{sup 2{minus}}{sub 3}/HCO{sup {minus}}{sub 3} that were quantified by H{sup 14}CO{sub 3} isotopic exchange. This exchange process was described very well using the computer program FITEQL and half-reactions for the surface exchange of HCO{sup {minus}}{sub 3}, CO{sup 2{minus}}{sub 3}, HSeO{sup {minus}}{sub 3}. The cosolutes SO{sub 4} and PO{sub 4} decreased SeO{sub 3} sorption by direct competition or site blockage, and these effects were also predicted using the surface exchange model. By contrast, the sorption of SeO{sub 3} was not influenced by Mg because the two ions sorbed over different pH regions and exchanged with different surface sites that appeared to be distinct and noninteractive. Evaluation of SeO{sub 3} sorption over a wide concentration range suggested that the surface of CaCO{sub 3}(s) was heterogeneous and that SeO{sub 3} had access to less than 5% of the total anion specific surface sites.

• OSTI ID: 6142461
• Journal Information: Geochimica et Cosmochimica Acta; (USA), Journal Name: Geochimica et Cosmochimica Acta; (USA) Vol. 54:8; 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
CHALCOGENIDES
CHEMISTRY
CONCENTRATION RATIO
DISSOLUTION
GEOCHEMISTRY
ION EXCHANGE
IONIC COMPOSITION
ISOTOPE RATIO
ISOTOPIC EXCHANGE
MINERALS
OXIDES
OXYGEN COMPOUNDS
PH VALUE
PHOSPHATES
PHOSPHORUS COMPOUNDS
SELENITES
SELENIUM COMPOUNDS
SELENIUM OXIDES
SOLUTES
SORPTION
SORPTIVE PROPERTIES
SULFATES
SULFUR COMPOUNDS
SURFACE PROPERTIES