Trace NaCl and Na2EDTA Mediated Synthesis of α-Calcium Sulfate Hemihydrate in Glycerol–Water Solution

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• 作者：Caiyun Jia ; Qiaoshan Chen ; Xu Zhou ; Hao Wang ; Guangming Jiang ; Baohong Guan
• 刊名：Industrial & Engineering Chemistry Research
• 出版年：2016
• 出版时间：August 31, 2016
• 年：2016
• 卷：55
• 期：34
• 页码：9189-9194
• 全文大小：374K
• 年卷期：0
• ISSN：1520-5045

文摘

We report a new class of glycerol–water system to transform FGD gypsum into α-calcium sulfate hemihydrate (α-HH) mediated by trace NaCl and Na₂EDTA to regulate the phase transformation rate as well as the crystal morphology to achieve crystals with high mechanical strength. NaCl plays a role in accelerating the nucleation and crystal growth process, whereas Na₂EDTA regulates the morphology of α-HH from columnar to lamellar. The paste made from columnar α-HH with higher aspect ratio deserves higher dry bending/compressive strength of 13.6/37.6 MPa, which is comparable with those prepared in nitrate–water medium, chloride–water medium, or by autoclave method. This study provides an improved alternative of glycerol–water system to transform FGD gypsum into α-HH with controlled morphology, high mechanical strength, and less corrosion to the equipment. We also establish the relationship between the mechanical strength of paste and the aspect ratio of α-HH crystals.