Thin-film composite

The membrane material is a thin-film composite in a 20-cm module. 

Fig. 12. A spinal-wound leveise osmosis membrane element (a) schematic depiction (b) cross section of a spinal-wound thin-film composite RO Filmtec...

Cellulose acetate, the earhest reverse osmosis membrane, is still widely used. Asymmetric polyamide and thin-film composites of polyamide and several other polymers have also made gains in recent years whereas polysulfone is the most practical membrane material in ultrafiltration appHcations. 

Thin film composite (TFC) is an ultrathin barrier membrane on polysulfone support layer, of good chemical stability. It has a wide operating pH range of 2.0 to 12.0 at 0 to 40 °C, but cannot tolerate chlorine. TFC membranes are better at rejecting silica than CA membranes. 

Sarangi, S. N. and Sahu, S. N. (2004). CdSe nanocrystalline thin films composition, structure and optical properties. Physica E, 23,159-167. 

Commercial interest in RO began with the first high-flux, high-NaCl-retention Loeb-Sourirajan anisotropic cellulose acetate membrane. Practical application began with the thin film composite (TFC) membrane and implementation for seawater desalination at Jeddah, Saudi Arabia [Muhurji et ak. Desalination, 76, 75 (1975)]. 

Although considerable research has been conducted with Pd-alloy foils, tubes, and thinner composite membranes, long-term durability and stability need to be further demonstrated, especially in the fuel reforming or WGS operating conditions, for acceptance of this technology in a commercial sector. Furthermore, mass-scale and cost-effective production of industrial-scale Pd-alloy thin-film composite membranes need to be demonstrated to be competitive in the hydrogen production and purification market. 

Thin-film balance apparatus, 12 7 Thin-film composite membranes, 21 633 Thin-film deposition, laser ablation for, 24 740... 

All oxidants used must be removed in the final stage of the pretreatment process, as they are known to damage most polymer membranes used for desalination. In particular, chlorine is known to be harmful to commonly used thin-film composite polyamide membranes. 

The geometries for asymmetric mixed-matrix membranes include flat sheets, hollow fibers and thin-fihn composites. The flat sheet asymmetric mixed-matrix membranes are formed into spirally wound modules and the hollow fiber asymmetric mixed-matrix membranes are formed into hollow fiber modules. The thin-film composite mixed-matrix membranes can be fabricated into either spirally wound or hollow fiber modules. The thin-film composite geometry of mixed-matrix membranes enables selection of different membrane materials for the support layer and low-cost production of asymmetric mixed-matrix membranes utilizing a relatively high-cost zeolite/polymer separating layer on the support layer. 

Silicalite-1 Selective layer PDMS Support PEI NA Thin-film composite fiat sheet Gas separations (e.g., O2/N2) Liquid separations (e.g., ethanol/water separation) [82]... 

Thin-Film Composite Mixed-Matrix Membranes... 

Thin-film composite mixed-matrix membranes can be made by a coating method or by a dual-layer co-extrusion technology, as discussed in Section 11.5.2.2. 

Jia and coworkers prepared thin-film composite zeolite-filled silicone rubber membranes by a dip-coating method [82]. The membranes have a thin silicalite-1/ silicone rubber mixed-matrix selective layer on top of a porous polyetherimide support. 

The new concept of using mixed-matrix membranes with commercially attractive thin-film composite geometry for desalination of water has been demonstrated by Jeong and coworkers [83]. 

Limited testing on chlorine sensitivity of poly(ether/amidel and poly(ether/urea) thin film composite membranes have been reported by Fluid Systems Division of UOP [4]. Poly(ether/amide] membrane (PA-300] exposed to 1 ppm chlorine in feedwater for 24 hours showed a significant decline in salt rejection. Additional experiments at Fluid Systems were directed toward improvement of membrane resistance to chlorine. Different amide polymers and fabrication techniques were attempted but these variations had little effect on chlorine resistance [5]. Chlorine sensitivity of polyamide membranes was also demonstrated by Spatz and Fried-lander [3]. It is generally concluded that polyamide type membranes deteriorate rapidly when exposed to low chlorine concentrations in water solution. 

U-1 Fluid Systems TFC-RC-100 Poly(ether/urea) (thin film composite)... 

By contrast, membranes U-1, A-2 and X-2 are all chlorine sensitive, each responding in a unique manner. U-1 is a thin film composite membrane, the active layer consisting of cross-linked poly(ether/urea) polymer. A-2 is a homogeneous aromatic polyamide containing certain polyelectrolyte groups. X-2 is a thin film composite membrane of proprietary composition. 

The structure of the so-called "composite" membranes used in reverse osmosis is also much more complex than the conventional, simplistic description of the ultrathin semipermeable film deposited on and supported by a porous substrate. Most of these membranes which exhibit high flux and separation are composed of an anisotropic, porous substrate topped by an anisotropic, ultrathin permselective dense layer which is either highly crosslinked, or exhibits a progressively decreased hydrophilicity toward the surface. The basic difference between the conventional anisotropic (asymmetric) membrane and the thin film composite is that the latter might be... 

Thin-Film Composite Reverse-Osmosis Membranes Origin, Development, and Recent Advances... 

The origin of thin-film-composite reverse osmosis membranes began with a newly formed research institute and one of its first employees, Peter S. Francis. North Star Research and Development Institute was formed in Minneapolis during 1963 to fill a need for a nonprofit contract research institute in the Upper Midwest. Francis was given the mission of developing the chemistry division through support, in part, by federal research contracts. At this time the Initial discoveries by Reid and Breton ( ) on the desalination capability of dense cellulose acetate membranes and by Loeb and Sourlrajan (,2) on asymmetric cellulose acetate membranes had recently been published. Francis speculated that improved membrane performance could be achieved, if the ultrathin, dense barrier layer and the porous substructure of the asymmetric... 

A significant advance was made in the art of thin-film-composite membranes by Cadotte in 1970 with the advent of the NS-lOO membrane ( 5). This reverse osmosis membrane contained an ultrathin aryl-alkyl polyurea formed Insltu on a mlcroporous polysul-... 

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