基于道南效应和溶解-扩散效应分析低浓度乙醇中绿原酸的纳滤分离规律

Analyze nanofiltration separation rule of chlorogenic acid from low concentration ethanol by Donnan effect and solution-diffusion effect

该文采用纳滤分离低浓度乙醇中绿原酸,探索道南效应和溶解-扩散效应对绿原酸分离的影响规律。实验表明溶液pH、乙醇浓度影响绿原酸分离行为,30%乙醇中绿原酸pH 3~7,截留率相差70.27%,通过响应面法建立二次回归模型,纳滤膜截留相对分子质量、溶液pH、乙醇浓度存在交互作用,绿原酸存在状态决定了其分离行为,随着乙醇浓度的增加,游离态绿原酸因溶解-扩散效应易吸附溶解在膜表面而促进其透过,解离态绿原酸在道南效应和溶解-扩散效应的双重作用下,难以进入膜表面,而截留率显著升高。优选出的纳滤富集工艺相较于传统减压浓缩优势明显,解决了中药分离精制过程中,低浓度有机试剂环境中中药成分在溶剂回收时存在效率低下、成分损失严重的技术难题。

To separate chlorogenic acid from low concentration ethanol and explore the influence of Donnan effect and solution-diffu- sion effect on the nanofihration separation rule. The experiment showed that solution pH and ethanol volume percent had influences on the separation of ehlorogenic acid. Within the pH values from 3 to 7 for chlorogenic acid in 30% ethanol, the rejection rate of chloro- genic acid was changed by 70. 27%. Through the response surface method for quadratic regression model, an interaction had been found in molecule weight cut-off, pH and ethanol volume percent. In fixed nanofihration apparatus, the existence states of ehlorogeuie acid determinedits separation rules. With the increase of ethanol concentration, the free form chlorogenic acid was easily adsorbed, dis- solved on membrane surface and then caused high transmittance due to the solution-diffusion effect. However, at the same time, due to the double effects of Donnan effect and solution-diffusion effect, the ionic state of chlorogenic acid was hard to be adsorbed in mem- brane surface and thus caused high rejection rate. The combination of Box-Behnken design and response surface analysis can well opti-mize the concentrate process by nanofihration, and the results showed that nanofihration had several big advantages over the traditional vacuum concentrate technology, meanwhile, and solved the problems of low efficiency and serious component lossesin the Chinese med- icines separation process for low concentration organic solvent-water solution.