Effect of Supersaturation on Competitive Nucleation of CaSO4 Phases in a Concentrated CaCl2 Solution

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• 作者：Hailu Fu ; Baohong Guan ; Guangming Jiang ; Matthew Z. Yates ; Zhongbiao Wu
• 刊名：Crystal Growth & Design
• 出版年：2012
• 出版时间：March 7, 2012
• 年：2012
• 卷：12
• 期：3
• 页码：1388-1394
• 全文大小：397K
• 年卷期：v.12,no.3(March 7, 2012)
• ISSN：1528-7505

文摘

Nucleation is a combined result of thermodynamics and kinetics. Calcium sulfate dihydrate (DH), 伪-calcium sulfate hemihydrate (伪-HH), and calcium sulfate anhydrite (AH) all have the potential to precipitate when the solution is supersaturated with them at the same time. The effect of supersaturation on CaSO₄ phase鈥檚 occurrence was investigated in a 3.00 m CaCl₂ solution at 91 掳C to better understand the kinetics of competitive nucleation. In a wide range of supersaturations, DH and 伪-HH precipitated concomitantly without AH forming. The molar fraction of 伪-HH in the precipitate increased gradually from 47.23% to a summit of 98.91% when the supersaturation (S_HH) varied from 1.90 to 3.76 and then followed a dramatic decrease to 18.77% with a further increase in S_HH to 6.26. The predominant nucleation shifted from 伪-HH at the lower supersaturations to DH at the higher supersaturations. The crystallization rate evolution with supersaturation was responsible for the growth and decline of DH and 伪-HH in the precipitate.