流动电势法对L-谷氨酸水溶液结晶过程的表征

Characterization of the crystallization of L-glutamic acid by streaming potential measurements

以流动电势法研究L-谷氨酸饱和水溶液的降温结晶过程,考察了溶液起始温度和酸度对结晶过程中流动电势(ν)-结晶器温度(t)曲线的影响。结果表明:起始温度为15℃的L-谷氨酸饱和溶液在较高酸度条件(pH<3.5)下成核明显,25℃下等电点附近有成核能力,30℃下在不同酸度下均显示一定的成核能力;pH=2.5、pH=3.5的L-谷氨酸饱和溶液,只在起始温度15℃下可形成晶核;pH=3.0的饱和溶液在起始温度25和30℃下可有效地形成晶核。运用生长基元理论对此结晶过程进行了分析。

The streaming potentials of saturated solutions of L-glutamic acid（L-Glu） were determined in order to characterize the crystallization occurring during a cooling process.The influence of varying the initial temperature and solution acidity on the ν-t curves were investigated.The results showed that： saturated solutions of L-Glu with relatively high acidity（pH3.5） had a distinct nucleating ability at an initial temperature of 15 ℃;solutions with an initial temperature of 25 ℃ showed competitive nucleating ability at or near the acidity of the isoelectric point;solutions with an initial temperature of 30 ℃ showed a certain nucleating ability which depended on the acidity.Saturated solutions of L-Glu with pH=2.5 and pH=3.5 could form crystal nuclei only when the initial temperature was 15 ℃;a solution with acidity pH=3.0 could efficiently form crystal nuclei at initial temperatures of 25 ℃ and 30 ℃.Growth unit theory can be employed to explain this crystallizing process.