表面活性剂对丁二酸冷却结晶动力学的影响研究

Influence of Surfactants on Cooling Crystallization Kinetics of Succinic Acid

杂质可以影响结晶过程中晶体的成核与生长,其影响一般由杂质在晶面上的吸附而导致的溶质固液界面能改变引起。本文基于表面活性剂双亲结构所具有的界面效应,以丁二酸冷却结晶体系作为研究对象,考察了表面活性剂对晶体生长过程的影响。发现表面活性剂可以明显地抑制晶体的生长速率;运用Malkin提出的描述过饱和度和晶体生长速率关系的理论模型对表面活性剂的影响过程进行分析,发现在表面活性剂存在下晶体表面被吸附的溶质分子的密度要明显小于纯水体系。

Impurity can influence the crystal nucleation and growth progress. The influence usually attributed to the adsorption of impurity on face of crystal, which is the key factor to change solid-liquid interface energy. In this work succinic acid was selected as model system and the surfactants was used as the impurity due to its interfacial effect which is caused by its amphiphilic structure. The cooling crystallizations were conducted in the presence of three surfactants separately, and the crystal growth rates were measured respectively in the presence of different surfactants. Results show that the presence of surfactants inhibits the crystal growth obviously. The mechanism underlying the effect of three surfactants on crystal growth was further studied with the theoretical model proposed by Malkin which describes the relation between the face growth rate and the degree of supersaturation in the surface integration step. It shows that the three surfactants decrease the density of adsorbed molecules of the crystallizing solute on the surface of the crystal.