The Application and Transport Mechanism of Nanofiltration in Organic Phase
Nanofiltration (NF) as a membrane technique has been gaining popularity over the past few years in the water treatment. Organic solvent nanofiltration (OSN) may be considered as an extension to the NF process for separating organic mixtures on a molecular level. Due to its gentleness, cleanness and low-cost, OSN has been found to be effective in a variety of industrial processes, such as food, homogeneous catalysis, pharmaceutical and petrochemical industries. In our recent work, the feasibility of recovering the solvent from the aqueous ethanol solution of soybean isoflavones and glabridin with nanofiltration (NF) was studied. The central composite design (CCD) of the response surface methodology (RSM) was applied to model the effects of temperature, pressure, and feed concentration on the permeate flux and the total solute retention. The results indicate that the developed models were in good agreement with the experimental results and they can be used to predict this NF process. However, the transport mechanism through NF membranes is still being debated, which will hinder the industrial applications of OSN. In order to understand and possible predict fluxes and retention for a certain membrane, the transport mechanism of solvents and solutes through NF membranes should be thoroughly understood. In this study, a new semi-empirical solvent transport model based on the solution-diffusion with imperfection model has been developed. In the newly developed model solvent permeability was found to be dependent on four parameters (solvent viscosity, dielectric constant, membrane-solvent solubility parameter difference and membrane-solvent surface tension difference). The result of the model fitting was well satisfactory for both pure solvent and binary solvent mixtures. In addition, in membrane filtration process, the size and shape of a molecule significantly affects a solute on its transport and retention characteristics. A novel and explicit size descriptor, the “calculated mean size (dc), has been proposed for the description of molecular shape in the solvent. The correlation between solute retention and different molecular geometric sizes is evaluated based on large amount of reference data. Analysis results show that “calculated mean size gives a better description of the solute retention by NF membranes in all cases, which justify its suitability as a universal size parameter used in the retention modeling.In a word, OSN is a potential lab-scale technique for day-by-day use to facilitate multi-step organic syntheses involving solvent-intensive column purifications, salting-out steps, batch adsorption, crystallization, etc. Furthermore, the membrane transport mechanism in organic phase and its modeling will receive attention in order to understand the OSN process and the membrane performances better.
Nanofiltration Organic Solvent Transport Mechanism
Fengchun Zheng Qipeng Yuan Qingxi Zhang Jiao Lv
State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029, PR China
国际会议
International Symposium on Crystal Engineering and Drug Delivery System 2009(2009晶体工程与药物传送系统国际会议)
天津
英文
72-73
2009-09-05（万方平台首次上网日期，不代表论文的发表时间）