Solubility and surface spectroscopy of zinc precipitates on calcite

Journal Article · Sat Dec 31 23:00:00 EST 1988 · Geochimica et Cosmochimica Acta; (USA)

DOI:https://doi.org/10.1016/0016-7037(89)90268-8· OSTI ID:7145094

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

---

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

The sorption and precipitation of Zn was investigated in equilibrium calcite (CaCO{sub 3(S)}) suspensions at Zn concentrations that approached and exceed the solubility of known zinc carbonate solids. Surface-enhanced precipitation was not observed and CaCO{sub 3(S)} did not nucleate Zn solids when the aqueous ion activity product (IAP) was below the equilibrium IAP of the least soluble, kinetically viable Zn phase. The CaCO{sub 3(S)} surface was not requisite for Zn precipitation. When CaCO{sub 3(S)} was present the precipitate formed a surface coating or discrete Zn particles bound to the surface. X-ray photoelectron spectroscopy, X-ray diffraction, and energy dispersive X-ray spectrometry of both Zn-treated CaCO{sub 3(S)} and isolated Zn particles implied, but did not confirm, that the precipitate was hydrozincite or its hydrated form. Zinc-treated calcite maintained Zn concentrations that agreed with the solubility of a synthetic hydrozincite measured by Schindler et al (1969). Direct measurements showed that the equilibrium solubility of the precipitate exceeded that of a natural hydrozincite and was less than a natural smithsonite (log IAP = a{sub Zn{sup 2+}}a{sub CO{sub 3}{sup 2{minus}}} = {minus}10.53 {plus minus} 0.10). It is suggested that a poorly ordered form of hydrozincite that regulates Zn activities at higher levels than well-crystallized natural varieties readily precipitates in CaCO{sub 3(aq)}/CaCO{sub 3(S)} systems. The environmental significance of this phase is unknown.

• OSTI ID: 7145094
• Journal Information: Geochimica et Cosmochimica Acta; (USA), Journal Name: Geochimica et Cosmochimica Acta; (USA) Vol. 53:1; ISSN GCACA; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
ALKALINE EARTH METAL COMPOUNDS
CALCITE
CALCIUM CARBONATES
CALCIUM COMPOUNDS
CARBON COMPOUNDS
CARBONATE MINERALS
CARBONATES
CHEMICAL COMPOSITION
CHEMISTRY
DISSOLUTION
EQUILIBRIUM
GEOCHEMISTRY
MINERALOGY
MINERALS
NUCLEATION
OXYGEN COMPOUNDS
PRECIPITATION
SEPARATION PROCESSES
SOLUBILITY
SORPTION
SPECTROSCOPY
SURFACE PROPERTIES
ZINC COMPOUNDS