The seeded growth of calcium sulfate dihydrate crystals in NaCl solutions up to 6 m and 90 C
- Rice Univ., Houston, TX (United States). Dept. of Environmental Science and Engineering
The kinetics of calcium sulfate crystal growth is of importance in various fields, such as geochemistry, desalination technology, petroleum industry, and water and wastewater treatment. The seeded crystal growth rate of calcium sulfate dihydrate was measured as a function of supersaturation in NaCl electrolyte solutions from 0 to 6 m at temperatures of 25, 50, 70, and 90 C. The growth followed a second-order parabolic rate law with activation energies greater than 53 kJ/mol which suggested the surface reaction as the rate-limiting step. It was observed that the rate constant and the activation energy are solution composition dependent. The rate constant increases with NaCl concentration up to 3 molal and then begins to fall slightly. The activation energy dropped from 61 kJ/mol in the pure Ca-SO[sub 4]H[sub 2]O system to 53 kJ/mol in 3.0 m NaCl solutions. The electrolyte effect was similar to the crystal solubility behavior in aqueous electrolyte solutions resulting from the variation of the mean activity coefficient of the crystal with ionic strength. The rate constant is proportional to the crystal solubility and inversely proportional to the edge work or the interfacial tension as expected in the classic BCF model.
- OSTI ID:
- 7207449
- Journal Information:
- Journal of Colloid and Interface Science; (United States), Journal Name: Journal of Colloid and Interface Science; (United States) Vol. 163:2; ISSN 0021-9797; ISSN JCISA5
- Country of Publication:
- United States
- Language:
- English
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360602* -- Other Materials-- Structure & Phase Studies
ALKALI METAL COMPOUNDS
AQUEOUS SOLUTIONS
BRINES
CHLORIDES
CHLORINE COMPOUNDS
CRYSTAL GROWTH
DEPOSITION
DISPERSIONS
FOULING
GYPSUM
HALIDES
HALOGEN COMPOUNDS
MINERALS
MIXTURES
SAMPLE PREPARATION
SODIUM CHLORIDES
SODIUM COMPOUNDS
SOLUTIONS
SULFATE MINERALS