红豆杉多糖浸提过程动力学模型

Kinetic model for polysaccharide's extraction from Taxus by water

对红豆杉多糖热水浸提的过程进行了动力学分析并建立了动力学模型.该模型适用于原料是细颗粒的外扩散控制过程,并且原料中溶质含量较大,溶质在溶剂中的溶解度相对较小.模型的主要特点是:将浸水后的原料看成由固相和渗透水相两相组成,并考虑多糖从固相到渗透水相的持续溶出效应,即在浸提起始阶段,少部分溶质溶出到渗透水相使其达到溶解饱和,然后剩余溶质不断溶出并维持渗透水相处于该饱和状态,这个阶段称为"饱和扩散"阶段,是多糖浸提的主要阶段.模型能较好地反映红豆杉多糖的浸提过程.根据"持续溶出效应",本文对内扩散控制模型和溶出速率控制模型进行了讨论,最后还讨论了溶质浓度-扩散系数间的关系及对本模型的影响.

Based on the kinetic analysis of polysaccharide＇s extraction by water from Taxus, a kinetic model was set up. It can be applied when the process is controlled by ＂external diffusion＂, i.e. the material particles are so fine that the rate limiting step is the solute＇s diffusion from the surface of the particles into the bulk of the solvent, and the content of the solute in the material is excessive in comparison with its small solubility. The soaked material is regarded as consisting of two phases： solid and penetrated water. At the starting stage of the polysaccharide＇s extraction, when the water penetrates into the solid material, only small part of the solute is released into water to make it saturate, most of it remaines in the solid. After that stage, the penetrated water is kept in the saturation for a long time because the continuous dissolution of the solute in the solid. This stage which is called ＂stage of saturation diffusion＂ is the main extraction stage. The model could describe the process well. According to the effect of ＂the continuous solute dissolution＂, the kinetic models for the bioactive substance＇s extraction from plants controlled by ＂internal diffusion＂ and by ＂solute＇s dissolution＂ were discussed. The influence of the relation between solute concentration and diffusion coefficient on the model was also discussed.