Cellulose acetate blend membranes properties

In the woik of Olde Riekerink et al. (2002), one type of UF (cellulose triacetate, CTA) membrane and one type of RO (cellulose acetate blend, CAB) membrane were selected for CO2 plasma modification. CTA ultrafilters are well known for their low fouling properties and CAB membranes are widely used for desalination. CO2 plasma treatment resulted in the gradual etching of the membrane s dense top layer. 

Several authors have discussed the ion exchange potentials and membrane properties of grafted cellulose [135,136]. Radiation grafting of anionic and cationic monomers to impart ion exchange properties to polymer films and other structures is rather promising. Thus, grafting of acrylamide and acrylic acid onto polyethylene, polyethylene/ethylene vinyl acetate copolymer as a blend [98], and waste rubber powder [137,138], allows... 

The membrane surfaces have also been grafted or coated with polyacrylamide, poly(acrylic acid) [70, 71], poly(vinyl alcohol) and cellulose derivatives [72]. Another possibility for improving the membrane properties is the use of polymer blends. Blends of PVDF/PVP [73, 74], PVDF/poly(ethylene glycol) (PEG) [75], PVDF/sulfonated polystyrene [76], PVDF/poly(vinyl acetate) [77] and PVDF/ poly(methyl methacrylate) [78] have been used in the preparation of micropor-ous membranes. 

Commercial membranes for CO2 removal are polymer based, and the materials of choice are cellulose acetate, polyimides, polyamides, polysulfone, polycarbonates, and polyeth-erimide [12]. The most tested and used material is cellulose acetate, although polyimide has also some potential in certain CO2 removal applications. The properties of polyimides and other polymers can be modified to enhance the performance of the membrane. For instance, polyimide membranes were initially used for hydrogen recovery, but they were then modified for CO2 removal [13]. Cellulose acetate membranes were initially developed for reverse osmosis [14], and now they are the most popular CO2 removal membrane. To overcome state-of-the-art membranes for CO2 separation, new polymers, copolymers, block copolymers, blends and nanocomposites (mixed matrix membranes) have been developed [15-22]. However, many of them have failed during application because of different reasons (expensive materials, weak mechanical and chemical stability, etc.). 

The research indicates a good compatibihty in the ethylcellulose/cellulose acetate system, whereas the thermal stabihty of mixtiu-es is improved compared to that of pure ethyl cellulose [142], Thus, this blend met the best equilibrium conditions at the membrane-solution interface of membrane separation in liquid chromatography experiments. In this context, knowledge on the interaction force between solute and interface of the membrane is necessary. It is observed that the interfacial adsorption properties and hydrophilidty of ethylcellulose are improved when blending the solution with cellulose acetate, and also that the alloys are superior to ethylcellulose in the separation efficiency for non-dissociable polar organic solutes. The obtained results are useful especially for orientational membrane fabrication. 

Rahimpour, A. and Madaeni, S. S. 2007. PolyethersuHone (PES)/cellulose acetate phthalate (CAP) blend ultrafiltration membranes Preparation, morphology, performance and antifouling properties. J. Memb. Sci. 305 299-312. 

---