浸取中和法脱除磷石膏中杂质的研究

以硫酸为浸取剂对磷石膏进行热浸处理，采用石灰乳中和调节磷石膏酸度，考察了反应温度、反应时间和硫酸浓度对磷石膏中杂质磷、氟、铁和铝的脱除情况的影响。同时，采用扫描电镜、热重分析仪和X射线衍射仪分析了处理前后磷石膏形貌、热稳定性和晶型结构的变化。结果表明：温度为85 ℃，硫酸质量分数为30%，反应45 min时，磷和氟的脱除率均能达到90%左右，铝脱除率能达到80%，铁脱除率大于20%，石膏pH≥7.0。处理后的石膏粒径减小非常明显，热稳定性有一定提高，且晶型更加稳定，能够完全满足建筑材料的要求。

Impurities removal from phosphogypsum by leaching neutralization method

The effects of temperature，time，and mass fraction of sulfuric acid on the removal of P，F，Fe2O3，and Al2O3 impurities from the phosphogypsum were investigated in the process of phosphogypsum leached by H2SO4 and the acidity was adjusted with lime milk.The microstructure，thermostability，and crystal structure of phosphogypsum before and after treatment were carefully analyzed by scanning electron microscope（SEM），thermogravimetric analysis（TG），and X ray diffraction （XRD）.Results showed that the optimum conditions as follows: the leaching temperature was 85 ℃，the leaching time was 45 min，the mass fraction of H2SO4was 30%.Under the optimal conditions，the removal percents of P and F were both achieved about 90%，Al2O3 removal rate was 80%，Fe2O3 removal rate was over 20%，and pH of phosphogypsum was at least 7.0. Phosphogypsum leached with H2SO4 showed sharply decreased particle size，but higher thermostability，and more stable structure.It was concluded that it could meet the requirements for the building materials.