Synthesis of Needle-like Aragonite from Limestone without Calcinations in the Presence of Magnesium Sulfate

Authors: Hu, Zeshan¹; Shao, Minghao²; Cai, Qiang²; Jiao, Zhaojie²; Zhong, Chenhua²; Deng, Yulin³

Source: Advanced Composite Materials, Volume 18, Number 2, 2009 , pp. 187-195(9)

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Abstract:

Much attention has been paid to the processing of inorganic whisker, especially calcium carbonate whisker, which can be used as reinforcement materials of polymer composite due to its low price. Unfortunately, the present synthesis technique of calcium carbonate whisker starts from calcinations of limestone, which involves high energy consumption and furthermore is a highly environment polluting reaction. In this report, needle-like aragonite was synthesized with a reversible solution reaction from limestone without calcination. Optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques were used to characterize the morphology and crystal structure of intermediates as well as that of the product, aragonite. GCC (grinding calcium carbonate) powder was dissolved in an aqueous solution of magnesium sulfate with reflux and air flush. EDTA titration was used to evaluate reaction rate of the dissolution. A kinetics equation of the dissolution reaction was constructed, which displayed second-order kinetics with respect to the concentration of magnesium sulfate. A rate constant of 0.0015 l^-3 · mol^-1 · h^-1 was obtained. The dissolution reaction gave fiber-like magnesium hydroxide sulfate and gypsum crystal. Then needle-like aragonite with a length of 9.13 ± 1.02 μm and an aspect ratio of 5.64 ± 1.37 was synthesized from the dissolution product with CO₂ bubbling at 70°C.

Keywords: ARAGONITE; SYNTHESIS; NEEDLE-LIKE; WHISKER; CALCIUM CARBONATE

Document Type: Research article

DOI: http://dx.doi.org/10.1163/156855109X428772

Affiliations: 1: Engineering Research Centre for Waste Oil Recovery Technology and Equipment, Ministry of Education, Chongqing Technology and Business University, Xuefu Avenue Nan'an District, Chongqing 400067, P. R. China;, Email: huzeshan2004@tom.com 2: Engineering Research Centre for Waste Oil Recovery Technology and Equipment, Ministry of Education, Chongqing Technology and Business University, Xuefu Avenue Nan'an District, Chongqing 400067, P. R. China 3: School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, 500 10th Street N.W., Atlanta, Georgia, USA 30332-0620

Publication date: 2009-05-01

Synthesis of Needle-like Aragonite from Limestone without Calcinations in the Presence of Magnesium Sulfate

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