过硼酸钠结晶介稳区的测定

Measurement of the Metastable Zone of Sodium Perborate Tetrahydrate

采用激光测定装置测定了过硼酸钠的溶解度和超溶解度,重点研究了过硼酸钠的溶解度、超溶解度以及结晶介稳区的变化规律,获得了过硼酸钠溶液的结晶介稳区,并用Apelblat方程对过硼酸钠的溶解度数据进行了关联。研究了降温速率、搅拌速率、六偏磷酸钠及聚丙烯酸钠添加量对过硼酸钠介稳区宽度的影响规律。研究结果表明,过硼酸钠溶解度随温度升高而增大,过硼酸钠的介稳区宽度在高温区较小而在低温区较大;降温速率的增大使过硼酸钠介稳区宽度变大,搅拌速率的增大使介稳区宽度变小;加入0.065%六偏磷酸钠和0.045%聚丙烯酸钠时获得的介稳区宽度最大。

The metastable zone is one of the most important properties of the crystallization process. In the present study the solubility and supersolubility of sodium perborate tetrahydrate （SPT） in water were measured by the laser detection technique. The dependence of the solubility and supersolubility on the temperature, cooling rate, stirring rate and concentrations of additives was discussed carefully. The curves of solubility and supersolubility were obtained and the empirical equation of the solubility for sodium perborate was employed to fit the data of sodium perborate solubility. The experimental results show that the solubility of SPT increases with the increase of temperature, the stable area of SPT becomes narrower at higher temperature, and the metastable zone increases with the increase of cooling rate and decrease of stirring rate. Further results show that the metastable zone width （MZW） of SPT is remarkably affected by the concentrations of additive agents and a maximum metastable zone is obtained when the concentrations of sodium hexametaphosphate and sodium polyacrylate are 0. 065% and 0. 045%, respectively.