LI Yaru ¹, DING Hongzheng ¹, ZHANG Xiaoting ¹, WANG Xiao ¹, WANG Jina ¹, MIAO Lei ²
(1. School of Chemistry and Materials Science, Henan University of Urban Construction, Pingdingshan 467036, Henan, China; 2. School of Physical Science and Engineering, Guangxi University, Nanning 530004, Guanxi, China)

Abstract: In order to explain the growth mechanism of desulphurized gypsum whisker in hydrothermal environment and improve its high value-added utilization, calcium sulfate whisker (HH-CSWs) was synthesized in sulfuric acid solution at 120 ℃ for 60 min under hydrothermal conditions. XRD curves of HH-CSW and desulfurized gypsum were fitted and refined by using Rietveld method. According to the Rietveld fitting results, the crystal structure model of HH-CSW and desulfurized gypsum was established. Their crystal structures are obviously different in two aspects. On one hand, there are 6 Ca-O-S bonds and2Ca-O-H bonds in the desulfurized gypsum structure, while there are 8 Ca-O-S bonds in the HH-CSW structure. On the other hand, the desulfurized gypsum structure has two H2O channels (along the c and a axes, respectively), whereas the HH-CSW structure has only one H2O channel. It can be concluded that, the formation of HH-CSW prepared by using hydrothermal method in flue gas desulfurization (FGD) is through the two Ca-O-H bonds in the structure of desulphurized gypsum break to release H₂O and the combination with S to form two new Ca-O-S bonds, so as to release H₂O molecules along the c-axis and lose part of the crystalline water to form HH-CSW. This can be used as a theoretical basis for preparing desulfurized gypsum whisker with high ratio of length to diameter.
Key words: desulfurized gypsum; HH-CSW; Rietveld fitting; crystal structure