Experimental determination of portlandite solubility in H sub 2 O and acetate solutions at 100-350C and 500 bars: Constraints on calcium hydroxide and calcium acetate complex stability

Journal Article · Fri Mar 01 00:00:00 EST 1991 · Geochimica et Cosmochimica Acta; (United States)

DOI:https://doi.org/10.1016/0016-7037(91)90331-X· OSTI ID:6038861

Seewald, J S; Seyfried, Jr, W E ^[1]

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1. Univ. of Minnesota, Minneapolis (United States)

The solubility of portlandite was measured in H{sub 2}O and aqueous acetate solutions of varying concentration (1-10 mmolal) at temperatures from 100-350C and 500 bars pressure. Dissolved Ca concentrations increased with decreasing temperature and increasing dissolved acetate concentration. Using known thermodynamic data for portlandite, H{sup +}, OH{sup {minus}}, Ca{sup ++}, CH{sub 3}COO{sup {minus}}, CH{sub 3}COOH{sup 0}, and H{sub 2}O{sub (1)}, stability constants for CaOH{sup +} and CaCH{sub 3}COO{sup +} complexes were determined. These results indicate that the stabilities of CaOH{sup 1} and CaCH{sub 3}COO{sup 1} complex increase with increasing temperature. In the acetate-free experiments, CaOH{sup +} is the dominant form of dissolved Ca in equilibrium with portlandite at 100-350C and 500 bars, while in the acetate-rich experiments (10 mmolal acetate), Ca{sup ++} and CaOH{sup +} are the dominant forms of Ca in equilibrium with portlandite at low temperature (100-200C) and CaCH{sub 3}COO{sup +} and CaOH{sup +} are the dominant forms at relatively high temperature (200-350C). Metal-acetate complexing has long been suggested as an important mechanism for mobilizing base metals during the formation of ore deposits in organic-rich environments. Due to the stability of CaCH{sub 3}COO{sup +} complex in Ca-bearing fluids at elevated temperatures and pressures, however, the effectiveness of dissolved acetate to enhance base metal sulfide solubility is limited.

• OSTI ID: 6038861
• Journal Information: Geochimica et Cosmochimica Acta; (United States), Vol. 55:3; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
58 GEOSCIENCES
CALCIUM HYDROXIDES
SOLUBILITY
THERMODYNAMIC PROPERTIES
PETROLEUM DEPOSITS
RESERVOIR ROCK
DIAGENESIS
HYDROTHERMAL ALTERATION
SULFIDE MINERALS
PRECIPITATION
ACETATES
AQUEOUS SOLUTIONS
BRINES
CALCIUM COMPLEXES
GEOCHEMISTRY
LEAD SULFIDES
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OIL WELLS
PRESSURE EFFECTS
TEMPERATURE EFFECTS
ZINC SULFIDES
ALKALINE EARTH METAL COMPLEXES
ALKALINE EARTH METAL COMPOUNDS
CALCIUM COMPOUNDS
CARBOXYLIC ACID SALTS
CHALCOGENIDES
CHEMISTRY
COMPLEXES
DISPERSIONS
GEOLOGIC DEPOSITS
HYDROGEN COMPOUNDS
HYDROXIDES
INORGANIC PHOSPHORS
LEAD COMPOUNDS
MINERAL RESOURCES
MINERALS
MIXTURES
OXYGEN COMPOUNDS
PHOSPHORS
PHYSICAL PROPERTIES
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SEPARATION PROCESSES
SOLUTIONS
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WELLS
ZINC COMPOUNDS
020200* - Petroleum- Reserves
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580000 - Geosciences