Polymorphism in CaCO₃ 鈥?Effect of temperature under the influence of EDTA (di sodium salt)

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• 作者：Shanmukha Prasad Gopi ; V.K. Subramanian ; ^{drvksau@gmail.com}
• 关键词：Calcium carbonate ; Calcite ; Vaterite ; Scale inhibition ; Morphology
• 刊名：Desalination
• 出版年：2012
• 期刊代码：24_00119164
• 类别：ce
• 出版时间：3 July, 2012
• 卷：297
• 期：Complete
• 页码：38-47
• 文件大小：2309 K

摘要

Crystallization behavior and polymorphism of CaCO₃ were studied at different temperatures (from 60 to 240 掳C) under the influence of ethylenediaminetetraacetic acid (EDTA). The samples were characterized using powder X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), Scanning electron microscope (SEM) and field emission scanning electron microscopy (FESEM). In the absence of EDTA, a calcite-aragonite binary mixture was resulted between 60 and 170 掳C above which calcite alone was formed. The presence of EDTA significantly influenced the crystallization behavior and composition of different polymorphs of CaCO₃ varied with temperature. Formation of a binary calcite-aragonite mixture at 60 掳C, ternary calcite-vaterite-aragonite mixture at 100 掳C, a binary aragonite-vaterite mixture at 130 掳C, a binary calcite-aragonite mixture at 170 掳C, purely aragonite at 200 掳C and vaterite with very little aragonite at 230 掳C confirmed that temperature affects the crystallization process in the presence of EDTA. Rhomboidal calcite, needle/rod like aragonite and flower like vaterite were obtained under different conditions. At 230 掳C, a unique flower like morphology was observed for vaterite. The efficacy of EDTA on CaCO₃ scale inhibition between 60 and 230 掳C is discussed.