为了制备电子级磷酸,采用了悬浮结晶法对工业磷酸进行提纯.分析了结晶法提纯工业磷酸的原理,并基于结晶过程中杂质的有效分配系数对多次结晶后杂质的分布建立了晶体纯度预测模型,同时考察了酸浓度、结晶次数和磷酸原料杂质初始含量对磷酸提纯效果的影响.研究结果表明,采用结晶法提纯磷酸具有良好的效果,能有效地脱除所考察的五种杂质(Li、Mg、Al、Cr、Mn);以一次晶体为原料,在磷酸浓度为84％的条件下,经过3次结晶,和在磷酸浓度为88％的条件下,经过4次结晶,均可以达到美国典型半导体磷酸要求.所建立的晶体纯度预测模型能很好地预测杂质浓度随结晶次数的变化.%In order to prepare electronic grade phosphoric acid, a combined theoretical and experimental approach was undertaken to find out the influences of phosphoric acid concentration, times of crystallization and the initial impurity concentration of raw materials on the purification process by suspension crystallization. A numerical model of crystal purity prediction used for the prediction of the impurity concentration after several times of crystallization was proposed on the basis of the effective distribution coefficient of impurity in the crystallization process. The experimental results indicate that the purification of phosphoric acid by crystallization is feasible, and the analysis results of the ICP-MS(inductively coupled plasma mass spectrometry) show that the removal results of the targeted 5 impurity ions (LKMg,AkCr,Mn) are satisfactory. The industrial grade phosphoric acid solution with 84%(wt) concentration was crystallized to get the phosphoric acid hemihydrate, and using it as raw material, the specification of United States Typical Semiconductor Acid can be reached after 3 times of crystallization with H3PO4 84 %(wt) concentration or 4 times of crystallization with H4PO4 88%(wt) concentration. The proposed numerical model of crystal purity prediction can be used to predict the change of impurity concentration with the times of crystallization.
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