脱硫石膏制备γ-CaSO_(4)晶须及Ⅱ-CaSO_(4)晶须

Preparation ofγ-CaSO_(4) and Ⅱ-CaSO_(4) whiskers using FGD gypsum

为了制备稳定的无水不溶硫酸钙(Ⅱ-CaSO_(4))晶须,提出改进的水热–焙烧工艺。以脱硫石膏为原料,在HCl-MgCl_(2)溶液中通过加压水热反应合成无水可溶硫酸钙(γ-CaSO_(4))晶须,焙烧得到Ⅱ-CaSO_(4)晶须。采用X射线衍射(XRD)和扫描电镜(SEM)等进行表征。实验结果表明,γ-CaSO_(4)晶须的最佳生长条件为:MgCl_(2)浓度为0.07 mol·L^(−1),脱硫石膏与水的质量比m(gypsum)/m(H2O)为0.09,HCl浓度为0.44 mol·L^(−1),反应温度为120℃,反应时间为2.5 h。在600℃焙烧后,制得长径比大、表面光滑且规整度高的Ⅱ-CaSO_(4)晶须。相比于传统的水热–焙烧工艺,以γ-CaSO_(4)晶须为中间产物的工艺避免了结晶水脱除对晶格的破坏,制得的Ⅱ-CaSO_(4)晶须结构致密,具有高稳定性。

An improved hydrothermal-calcination process was proposed to prepare anhydrous-insoluble calcium sulfate(Ⅱ-CaSO_(4))whisker with good stability.The anhydrous-soluble calcium sulfate(γ-CaSO_(4))whisker was synthesized by autoclave hydrothermal reaction in HCl-MgCl_(2)solution from flue gas desulfurization gypsum,and then calcined to obtainⅡ-CaSO_(4)whisker.X-ray diffraction(XRD),scanning electron microscope(SEM)and other characterization techniques were used.The experimental results show that the optimum growth conditions ofγ-CaSO_(4)whisker are MgCl_(2)concentration of 0.07 mol·L^(−1),mass ratio of desulfurization gypsum to water m(gypsum)/m(H2O)=0.09,HCl concentration of 0.44 mol·L^(−1),reaction time of 2.5 h and reaction temperature of 120℃.After calcination at 600℃,Ⅱ-CaSO_(4)whisker featuring large aspect ratio,smooth surface,and high regularity could be obtained.Compared with the conventional hydrothermal-calcination method,usingγ-CaSO_(4)whisker as the intermediate product circumvent the destruction of crystal lattice due to the release of crystal water,thus endowing the obtainedⅡ-CaSO_(4)whisker with dense structure and high stability.