The Effects of Inorganic Additives on the Nucleation and Growth Kinetics of Calcium Sulfate Dihydrate Crystals

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• 作者：Taher RabizadehTomasz M. Stawski ; David J. Morgan ; Caroline L. Peacock ; Liane G. Benning
• 刊名：Crystal Growth & Design
• 出版年：2017
• 出版时间：February 1, 2017
• 年：2017
• 卷：17
• 期：2
• 页码：582-589
• 全文大小：575K
• ISSN：1528-7505

文摘

The effects that 50–500 mM aqueous Li⁺, Na⁺, K⁺, and Mg²⁺ have on the crystallization kinetics of calcium sulfate dihydrate (gypsum; CaSO₄·2H₂O) were determined by in situ and time-resolved UV–vis spectrophotometry. The mechanisms of surface or structural associations between these additives and the end-product gypsum crystals were evaluated through a combination of inductively coupled plasma mass and/or optical emission spectrometric analyses of digested end-products and X-ray photoelectron spectroscopy of the surface of the solids. Furthermore, X-ray diffraction and scanning electron microscopy were utilized for determining any changes in phase composition and growth morphologies of the formed crystals. Our results revealed that Mg²⁺, even at low concentrations, decreased the nucleation and growth kinetics 5–10 fold more than Li⁺, Na⁺, and K⁺. In all cases, the additives also changed the shapes and sizes of the formed crystals, with Mg²⁺ and Li⁺ resulting in longer and narrower crystals compared to the additive-free system. In addition, we show that, regardless of concentration, Mg²⁺, Li⁺, and K⁺ only adsorb to the newly forming surfaces of the growing gypsum crystals, while ∼25% of Na⁺ becomes incorporated into the synthesized crystals.