磷酸结晶介稳区性质的研究

本研究利用激光散射法研究了不同浓度下磷酸介稳区宽度的变化,同时还系统地考察了降温速率、搅拌强度、晶种加入量及典型杂质离子对介稳区宽度的影响关系。结果表明,介稳区宽度随降温速率的增加而相应变宽,由此根据不同浓度和不同降温速率的磷酸介稳区数据得到磷酸的表观二次成核级数为3.3;搅拌强度的增加和晶种加入量的减小,均使得磷酸介稳区宽度呈现逐渐变窄的变化。几种典型的杂质离子对磷酸介稳区宽度加大的影响作用不同,Fe2+对介稳区宽度的作用最为明显,F-的影响效果相对最弱,按照影响效果的强弱区分为:Fe2+SO42-F-。

Crystallization Metastable Zone Width of Phosphoric Acid

The influences of different conditions, including the concentration of phosphoric acid, cooling rates, agitation intensity, amount of crystal seeds and adding of three typical impurity ions, respectively, on the phosphoric acid crystallization metastable zone width (MZW) were systematically studied by using laser light-scattering method in this paper. It was shown that the MZW of phosphoric acid would be enlarged with the increase of cooling rate; and an apparent secondary nucleation order of 2H_3PO_4·H_2O of 3.3 was obtained by modified regression method under cases with different concentrations and cooling rates. While with the increase of agitation intensity or decreasing amount of added crystal seeds, the MZW would be narrowed gradually. Though all the typical impurity ions (Fe~(2+), SO_4~(2-) and F~-) doped in phosphoric acid will enlarge the MZW, the phosphoric acid MZW variations are quite different. Among those impurity ions, the influence of Fe~(2+) on MZW is the largest, and the influence degrees of them are in the order as follows: Fe~(2+)＞SO_4~(2-)＞F~-.