MgSO_4/MgCl_2对脱硫石膏溶解度及其晶须结晶的影响

Effects of MgSO_4/MgCl_2 on FGD Gypsum Solubility and Whisker Crystallization

以预处理后脱硫石膏为原料,采用水热法制备了硫酸钙晶须。研究了添加剂MgSO_4、MgCl_2对晶须显微结构、长径比和脱硫石膏溶解度的影响,探讨了MgSO_4、MgCl_2在反应溶液体系中的解离特性及作用机理。研究结果表明:MgSO_4、MgCl_2都可以改善硫酸钙晶须的结晶,提高晶须的长径比,且不影响其物相组成。在MgSO_4添加量(质量分数)为2.0%、MgCl_2添加量(质量分数)为1.5%时,制备的晶须长径比分别为80和110。在反应溶液中,MgSO_4的加入降低了脱硫石膏的溶解度,同离子效应起主导作用,而MgCl_2的加入则增加了其溶解度。MgSO_4(0)中性离子对调节反应溶液中各离子浓度的相对稳定起主导作用,MgCl_2改善晶须结晶的作用效果优于MgSO_4。

Taking the purified flue-gas desulfurization( FGD) gypsum as raw material,the calcium sulfate whiskers were prepared by hydrothermal method.The effects of additive MgSO_4 or MgCl_2 on the microstructure,aspect ratio of whiskers and the solubility of treated FGD gypsum were investigated. The ionization and hydrolysis characteristics of MgSO_4 or MgCl_2 in the reaction solution and their mechanism were discussed. The results show that the crystallization of calcium sulfate whiskers can be improved and their aspect ratio can also be increased via the addition of MgSO_4 or MgCl_2,but the phase of whiskers remain unchanged. When the dosage( mass fraction) of MgSO_4 is 2.0% and the dosage( mass fraction) of MgCl_2 is 1.5%,the aspect ratio of the prepared whiskers is 80 and 110,respectively.The solubility of FGD gypsum is decreased by adding MgSO_4 into solution,because the common ion effect plays a dominant role. While the solubility of FGD gypsum is increased by MgCl_2. The effect of MgCl_2 on whisker crystallization is better than that of MgSO_4 because the neutral ion pairs of MgSO_4( 0)play a dominant role on the relative stability of the whole ions concentration.