pH与Ca2+浓度对磷石膏常压制备α-水硫酸钙的影响

摘要

研究了以Ca-Mg-K复合盐溶液为转晶体系中pH及Ca2+浓度对磷石膏常压水热法制备α-半水硫酸钙的影响.通过测定反应中固、液两相组成随时间的变化,得到了磷石膏在不同盐溶液体系当中的转晶速率.采用TE-SEM、XRD、TG等检测方法对产物做了表征,根据不同初始条件对最终产物晶体形貌的影响,讨论了不同条件下的影响机理.建立了以表面反应控制为基础的原料磷石膏溶孵动力学模型,拟合得到不同Ca2+浓度条件下的表观溶解反应速率常数及反应级数,结果表明:磷石膏的溶解过程属于表面反应控制,在Ca2+浓度为2.5～3.5 mol/L的中性环境中,其溶解反应表观反应级数相差不大,平均值为1.533.%The effects of pH and Ca2+ concentration on the reaction rate and crystal morphology of Ca-Mg-K hydrothermal salt solution method preparing α-hemihydrate calcium sulfate by phosphogypsum under atmospheric pressure were investigated.The conversion rates of phosphogypsum in different reaction conditions were obtained by measuring the change of solid and liquid phases in the reaction slurry.The products were determined and characterized by the means of TE-SEM,XRD,and TG.According to the effects of different initial conditions on the crystal morphology of products,the influencing mechanisms under different conditions were investigated.The raw material dissolution kinetics model was established based on surface reaction control mechanism,and the apparent reaction rate constant and reaction order under different initial conditions were obtained by fitting relative parameters.The results showed that the dissolution process of phosphogypsum was controlled by surface reaction.In the neutral environment of Ca2+ concentration of 2.5～3.5 mol/L,the apparent reaction order of dissolution reaction was numerical similarity,with an average value of 1.533.