Abstract
We have developed multilayer mixed matrix membranes (MMMMs) consisting of a selective mixed matrix membrane (MMM) top layer, a porous poly(acrylonitrile- co-methyl acrylate) [poly(AN-co-MA)] intermediate layer and a polyphenylene sulfide (PPS) nonwoven fabrics substrate. The selective MMM layer was formed by incorporating KA zeolite in poly(vinyl alcohol) (PVA) matrix followed by the cross-linking reaction of PVA with fumaric acid. The fumaric acid induced cross-linking reactions were confirmed by Fourier-transformation infrared (FTIR), and their effects on PVA thermal stability and glass transition temperature were characterized by thermolgravimetric analysis (TGA) and differential scanning calorimetry (DSC). The separation performance of the newly developed MMMMs was investigated in terms of permeance and selectivity (as well as flux and separation factor) with respect to zeolite content, feed temperature and composition for the ethanol-water separation by pervaporation. It is found that the separation performance of the MMMM is superior to that of multilayer homogenous membranes (MHM) containing no zeolite. For example, the MMMM with 20 wt.% KA zeolite loading exhibits a much higher selectivity than that of MHM (1279 versus 511) at 60°C if the feed is a mixture of 80/20 (wt.%) ethanol/water. In addition, the activation energy of the water permeation is significantly reduced from 16.22 to 10.12 kJ/mol after adding of KA zeolite into the PVA matrix, indicating that water molecules require a much less energy to transport through the MMMM because the presence of hydrophilic channels in the framework of zeolite. The excellent pervaporation performance of the MMMM is also resulted from the good contact between zeolite-incorporated and polymer matrix cross-linked by fumaric acid.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 113-122 |
| Number of pages | 10 |
| Journal | Journal of Membrane Science |
| Volume | 268 |
| Issue number | 2 |
| DOIs | |
| State | Published - Jan 15 2006 |
| Externally published | Yes |
Bibliographical note
Funding Information:A-type zeolites with a low Si/Al ratio of unity are strong hydrophilic material and have high affinities toward water and polar molecules nm that is larger than the kinetic diameter (0.264 nm) of water molecule but smaller than that (0.430 nm) of ethanol molecule [34,35] . KA zeolite has a nominal pore size of 0.3 [36] . Therefore, KA zeolite can be particularly well suited for the separation of ethanol and water mixtures, which is supported by the experiment results. Besides, a good adhesion between PVA matrix and zeolite particles as observed by the FESEM images is considered to be a key factor to cause high water/ethanol selectivities for the zeolite-incorporated MMMMs. Gao et al. also investigated the effect of zeolite content on PVA membrane performance for the separation of various alcohol solutions. They observed that the flux rose with increasing KA zeolite content, whereas the separation factor was maintained upon addition of zeolite until 11% and then decreased drastically. They concluded that this phenomenon was probably resulted from “leaks” around the zeolite during pervaporation once the zeolite load was high.
Keywords
- Cross-linked PVA
- Ethanol-water separation
- Fumaric acid
- KA zeolite
- Multilayer mixed matrix membrane
- PVA multilayer composite membrane
- Pervaporation
ASJC Scopus subject areas
- Biochemistry
- General Materials Science
- Physical and Theoretical Chemistry
- Filtration and Separation