为了阐释水热环境下的脱硫石膏晶须(Calcium Sulfate Whisker,HH-CSWs)的生长机理,以提高脱硫石膏(Flue Gas Desulfurization,FGD)的高附加值利用,在120 ℃的硫酸溶液中,保温时间为60 min的水热条件下合成了大长径比半水硫酸钙晶须.通过Rietveld方法拟合精修了 HH-CSW样品及脱硫石膏的XRD曲线.根据Rietveld拟合结果,建立了 HH-CSW样品及脱硫石膏的结构模型.晶体结构模型对比分析结果表明,脱硫石膏与HH-CSW晶须的晶体结构存在着明显区别:一是在脱硫石膏结构中有六个Ca-O-S键和两个Ca-O-H键,在HH-CSW结构中有八个Ca-O-S键;二是脱硫石膏结构中有两个H2O通道(分别沿c轴和a轴方向),而HH-CSW结构中只有一个H2O通道.据此可以推断脱硫石膏水热制备HH-CSW的形成机理是脱硫石膏结构中两个Ca-O-H键断裂释放H2O,并与S结合形成两个新的Ca-O-S键,沿c轴释放H2O分子从而失去部分结晶水形成了 HH-CSW,为制备大长径比脱硫石膏晶须提供理论依据.
Growth Mechanism of Desulfurized Gypsum Whisker with Rietveld Method
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 and 2 Ca-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.
万方数据
维普
