微波辐照下丁二酸对磷石膏制备半水石膏的影响

Effect of Succinic Acid on Preparation of Hemihydrate Gypsum from Phosphogypsum under Microwave Irradiation

微波辐照下使用磷石膏制备半水石膏,通过分析固相产物结晶水含量、化学成分及晶体微观形貌来研究半水石膏随转晶剂掺量及反应时间的变化规律。研究表明:微波辐照下以磷石膏为原料制备半水石膏,在无转晶剂及单掺丁二酸转晶剂两种情况下,磷石膏主要成分二水硫酸钙向半水硫酸钙晶体的转化率随时间均呈先增大后减小的趋势;无转晶剂时,转化率在60 min时达到96%,半水硫酸钙晶体长径比为21;掺入丁二酸(质量分数为0.02%)时,转化率在90 min时达到96%,半水硫酸钙晶体长径比减小至1.5,且随着丁二酸掺量的增加,对半水硫酸钙晶体微观形貌的调控作用不断增强,晶体的长径比不断减小;EDS能谱及傅里叶红外光谱分析表明,微波辐照下丁二酸应该是通过改变半水石膏晶体比表面自由能的方式调控半水石膏晶体的生长。

Phosphogypsum was used to prepare hemihydrate gypsum under microwave irradiation.The change rule of hemihydrate gypsum with the amount of crystal wodidier and reaction time were studied by analyzing the solid phase product crystal water content,chemical composition and crystal micromorphology.Studies have shown that under microwave irradiation,phosphogypsum is used as a raw material to prepare hemihydrate gypsum without adding crystal modifier and single doping succinic acid crystal modifier.Under these conditions,the conversion rate of calcium sulfate dihydrate to calcium sulfate hemihydrate crystals increases first and then decreases with time.Without crystal modifier,the conversion rate reaches 96%in 60 min,and the aspect ratio of calcium sulfate hemihydrate crystals is 21.When succinic acid(mass fraction of 0.02%)is added,the conversion rate reaches 96%in 90 min.The aspect ratio of calcium sulfate hemihydrate crystals reduces to 1.5,and with the increase of succinic acid content,the regulation of the microscopic morphology of calcium sulfate hemihydrate crystals is continuously enhanced,and the aspect ratio of crystals continuously reduces.EDS energy spectrum and Fourier infrared spectroscopy analysis show that succinic acid under microwave irradiation regulates the growth of hemihydrate gypsum crystals by changing the specific surface free energy of hemihydrate gypsum crystals.