纳滤纯化低聚壳聚糖制备液的膜污染

为了实现纳滤纯化低聚壳聚糖制备液技术的工业化,对纳滤过程中膜污染的形成进行研究,分析了电解质浓度对纳滤膜吸附层污染的影响和纳滤运行中的能量分布情况以及吸附层对电解质截留率的影响。结果发现,膜面吸附层污染与浓差极化存在复杂的交互影响。运行初期传质过程主要受浓差极化控制,低聚壳聚糖在膜面吸附形成的浓流层使浓差极化进一步加剧;随着低聚壳聚糖在膜面累积数量的增大,传质过程逐渐转变为吸附层结构和浓差极化共同控制。膜面吸附层的形成分为浓流层和致密层两个阶段,其中致密层是造成纳滤膜脱盐和操作性能恶化的主要原因,在操作过程中应及时控制和减缓该层的形成。

Study on membrane fouling formation in the course of chiitooligosaccharides solution purification with nano-filtration

Aimed at realizing the industrialization of the nanofiltration purification preparation of Chiitooligosaccharides solution,this paper introduces the research on the formation of membrane fouling in the course of purification Chiitooligosaccharides(COS) solution with nano-filtration(NF).The investigation into the effect of the electrolyte concentration on pollution of adsorption layer of the nanofiltration membrane,distribution of energy in nanofiltration run,and the effect of adsorption layer on electrolyte retention rate shows that there occurs a complex interactive influence between the concentration polarization caused by Na+、Ac-and COS adsorption layer on the membrane surface.In earlier stage of COS solution purification by NF,the concentration polarization mainly controls the mass transport process in NF membrane.The accumulating COS on membrane surface allows the adsorption layer structure to be gradually developed to become the control factor with the concentration polarization.The formation of colloidal adsorption layer on the NF membrane surfaces consists of a stagnant layer and a concentrated flowing layer which occurs as the main reason for desalting and deteriorating performance of NF membrane,necessitating the timely control and slowing down of the formation.