磷酸盐对石膏溶解性能的影响

Effect of Phosphate on the Solubility of Gypsum

以分析纯二水硫酸钙为研究对象,研究了磷酸盐种类及掺量对石膏溶解度的影响。采用XRD衍射仪和扫描电镜对样品的物相及微观结构进行了表征,分析了其影响机理。研究结果表明:随着磷酸盐掺量的增大,石膏的溶解度呈不断降低趋势。磷酸盐会选择性的吸附在石膏晶体表面呈现阳性的(120)、(111)面,包裹在晶体表面层,改变了石膏晶体不同晶面的相对生长速率,使得石膏晶体形貌由针柱状变为粗棒状,颗粒平均粒径变大,进而降低了石膏溶解性能。三种磷酸根对石膏溶解抑制作用排序为PO_4^(3-)>HPO_4^(2-)>H_2PO_4^-。

In this work,the effect of phosphate on the solubility of gypsum was studied,in which the analytically pure gypsum was applied to one research object,and its mechanism was discussed by analytical of the phase composition and microscopic structure of samples by XRD and SEM. The results show that with the increase of phosphate content,the solubility of gypsum trend to decrease. The phosphate can easily absorb on surface of calcium sulfate dihydrate,such as the surface of（ 120） 、（ 111）,which appear positive tension. The adsorbtion of phosphate not only decras the surfacial energy of crystal,but also inhibit the dissolution of calcium sulfate dihydrate by coverage of Ca_3（ PO_4）_2. While the absorbtion can change the relative growth rate of different faces,which would inhibit the growth of axial direction of gypsum crystal and result in the crystal morphology changing from flakiness to coarse rods,the average diameter of the grain increase and draw ratio decreased. The inhibition force of phosphates on the solubility of gypsum is PO_4^（3-）HPO_4^（2-）H_2PO_4^-.