Structural characteristic and formation mechanism of hemihydrate calcium sulfate whiskers prepared using FGD gypsum |
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| Institution: | 1. College of Materials Science and Engineering, Xi''an University of Architecture and Technology, Xi''an 710055, China;2. Key Laboratory of Solid Waste Treatment and Resource Recycle (Ministry of Education), Southwest University of Science and Technology, Mianyang 621010, China;3. College of Resources Engineering, Xi’an University of Architecture & Technology, Xi’an 710055, China;1. Key Laboratory for Special Area Highway Engineering of Ministry of Education, Chang’an University, Xi’an 710064, China;2. School of Civil Engineering and Architecture, Zhejiang Sci-Tech University, Hangzhou 310018, China;1. College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, 310058, China;2. Physical Science Division, Pacific Northwest National Laboratory, Richland, WA, 99352, USA;1. Department of Environmental Engineering, China Jiliang University, Hangzhou 310018, China;2. Engineering Research Center for Waste Oil Recovery Technology and Equipment, Ministry of Education, Chongqing Technology and Business University, Chongqing 400067, China;1. School of Chemistry and Chemical Engineering, Anhui Province Key Laboratory of Controllable Chemistry Reaction and Material Chemical Engineering, Hefei University of Technology, Tunxi Road 193, Hefei, 230009, PR China;2. Anhui Liuguo Chemical Co. Ltd, Tonggang Road 8, Tongling, 244021, PR China |
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| Abstract: | Hemihydrate calcium sulfate whiskers (HH-CSWs) were hydrothermally synthesized in a sulfuric acid solution at 120 °C for different holding times (20, 40, and 60 min). The phase structures and morphologies were characterized by XRD and SEM, respectively. The XRD pattern of the sample under 60 min was refined via the Rietveld fitting method. The structure models of the HH-CSW sample under a 60-min holding time was established based on Rietveld fitting results. No difference in the positions of diffraction peaks was determined. The as-prepared holding time increased the intensity and aspect ratio of the diffraction peaks of both samples. In the prepared HH-CSW structure, Ca–O polyhedron is a 12-sided polyhedron similar to that in the gypsum structure; the Ca atom is located in two positions in the one-unit cell; the H2O channel along the c-axis similar is O-shaped and bigger than that in hexagonal and monoclinic CaSO4·0.5H2O structures. Therefore, although the prepared HH-CSW crystals’ structure are similar to that of the reported hexagonal and monoclinic CaSO4·0.5H2O structures, they are not the same. The formation mechanism of HH-CSW from flue gas desulfurization (FGD) gypsum is discussed based on the analysis of gypsum structure. |
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| Keywords: | FGD gypsum HH-CSW Rietveld method Crystal structure |
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