Cellulose triacetate membranes

R/0 unit Reverse Osmosis Unit for water purification in small aquariums and miniature yard-ponds, utilizes a membrane under pressure to filter dissolved solids and pollutants from the water. Two different filter membranes can be used the CTA (cellulose triacetate) membrane is less expensive, but only works with chlorinated water and removes 50-70% of nitrates, and the TFC membrane, which is more expensive, removes 95% of nitrates, but is ruined by chlorine. R/0 wastes water and a system that cleans 100 gallons a day will cost ft-om 400 to 600 with membrane replacement adding to the cost. A unit that handles 140 gallons a day will cost above 700,00. 

Fluorescent cellulose triacetate membranes were prepared by incorporation of pyrene-butyric acid (219), and were applied to in situ detection of ground water contamination by explosives, based on fluorescence quenching by the nitro groups LOD 2 mg/L of DNT (220) and TNT (221) and 10 mg/L for RDX (276) the response follows the Stern-Volmer law for DNT and TNT442. 

Chen and Su [102] L-Glutamate L-Glutamic acid fermentation L-Glutamate oxidase/ onto a cellulose triacetate membrane Oxygen electrode ... 

Recently Sulzer, working with Grace Davison [35,59] and using polyimide, polysiloxane or polyurea urethane membranes, and ExxonMobil [60], using Nation or cellulose triacetate membranes, have described processes to separate sulfur compounds from various refinery streams. 

K.M. White, B.D. Smith, P.J. Duggan, S.L. Sheahan and E.M. Tyndall, Mechanism of Facilitated Saccharide Transport through Plasticized Cellulose Triacetate Membranes, J. Membr. Sci. 194, 165 (2001). 

Paugam, M.F. and Buffle, J. (1998) Comparison of carrier-facilitated copper (II) ion transport mechanisms in a supported liquid membrane and in a plasticized cellulose triacetate membrane. Journal of Membrane Science, 147, 207. 

Smith BD. Facilitated transport of sugars and amino acids through plasticized cellulose triacetate membranes. Polym Mater Sci Eng 1997 77 269-270. 

Seguira, M., Kikkawa, M., and Urita, S., Carrier-mediated transport of rare earth ions through cellulose triacetate membranes. J. Membr. Sci., 1989, 42 47-55. 

Gherroue, A., Kerdjoudj, H., Molinari, R., Seta, P., and Drioh, E., Eixed sites plasticized cellulose triacetate membranes containing crown ethers for silver(I), copper(ll) and gold(III) ions transport. J. Membr. Sci., 2004, 228 149-157. 

Sugiura, M., Effect of quaternary ammonium salts on carrier mediated transport of lanthanoid ions through cellulose triacetate membranes. Sep. Sci. Tech., 1993, 28 1453-1463. 

Fig. 92. Schematic and response curve of successive determination of hypoxanthine (HX) and inosine (HXR) with a multilayer electrode. l xanthine oxidase, 2 cellulose triacetate membrane, 3 nucleoside phosphorylase, 4 oxygen electrode. (Redrawn from Watanabe et al., 1986).

Table 11 shows the performance of polymeric and ceramic filters for the separation and concentration of yeast and E-coli suspensions. The ceramic filters, due to their superior mechanical resistance, can be backpulsed to reduce flux decline during concentration. This is illustrated in Fig. 19 for the filtration of yeast suspension with 0.45 pm microporous cellulose triacetate membrane. Polymeric membranes can be backwashed at pressures up to about 3 bar. The data in Fig. 20 show the flux improvement with backpulsing using 0.2 pm microporous alumina membrane. ... 

Figure 19. Filtration of yeast suspension with 0.45 nun microporous cellulose triacetate membrane. Initial yeast concentration, dry-g/L (O) 3 ( ) 8.

This is analogous to the extraction of sugars with boronic acids described earlier. The recovery of phenylalanine from a fermentation broth has been simplified by using a microporous poly(tetrafluoroethylene) membrane with tri-/j-octylmethylammonium chloride in toluene in the pores.133 Phenylalanine can also be separated using the quaternary ammonium salt with 2-nitrophenyl octyl ether in a cellulose triacetate membrane.134 Kerosene flowing in hollow fiber membranes can remove 99.9% of organic pollutants, such as benzene, p dichlorobenzenc, chloroform, and carbon tetrachloride, from wastewater outside the fibers.135... 

Xanthine oxidase cross-linked with glutaraldehyde into cellulose triacetate membranes and attached to a Teflon membrane on an oxygen electrode Hypoxanthine as an indicator of fish freshness [35]... 

A considerable amount of research has been done to develop a membrane of cellulose triacetate as this material is more stable to extremes of temperature and pH and it will better withstand chemical and biological attack. While the cellulose triacetate membranes operated quite well on a short term basis, they were prone to compact at an operating pressure of 400 psig, with the resultant loss of flux to an impractical level, in a short period of time. 

The solution coating technique was used in the preparation of the cellulose triacetate membrane discussed above. A solution of cellulose triacetate in chloroform was deposited on the porous support and the solvent was then evaporated leaving a thin film on the porous support. Thin film polymerization was used to prepare a polyfuran membrane barrier layer on polysulfone. In this case, the monomer furfuryl alcohol is polymerized in situ by adjustment of pH and temperature. This membrane proved to be highly susceptible to oxidizing agents and is of limited value. By far the most valuable technique in the formation of membrane barrier layers is interfacial polycondensation. In this method, a polymer is formed on the porous support surface at the interface of organic and aqueous phases by reaction of specific molecules dissolved in each phase. It is by this method that a number of polyamides and polyurea membrane barrier layers have been formed on polysulfone. Elements containing these membranes are available commercially. 

With a gelatin membrane entrapped between two dialysis membranes and containing 46 U/cm of enzyme, the H2O2 formation corresponds to only 110 mU/cm, ie, less than 1% of the initial enzyme activity (Figure 14-19). This indicates a large excess of enzyme in the membrane. Consequently, the membrane is diffusion controlled. The low apparent activity may be attributed mainly to the diffusion resistance of the dialysis membrane for glucose. On the other hand, the measured activity of the membrane containing 46 U/cm is already about 70% of the activity used for immobilization. This value approaches that expected for pure kinetic control of the process [287], The apparent activity of urease immobilized in a cellulose triacetate membrane was found to be 66% of the initially applied enzyme activity [288]. 

H. Yamagishi, K. Saito, S. Furusaki, T. Sugo and J. Okamoto, Permeability of Methyl Methacrylate Grafted Cellulose Triacetate Membrane, Chem. Mater., 2 (1990) 705. 

D. A. Cerqueira, G. Rodrigues Filho, R. M. N. Assun9ao, Cd. S. Meireles, L. C. Toledo, M. Zeni, K. Mello, and J. Duarte, Characterization of cellulose triacetate membranes, produced from sugarcane bagasse, using PEG 600 as additive, Polym. Bull, 60 (2008) 397-404. 

Seawater or brackish water can be purified by reverse osmosis. To maximise the flow of water through a polymer membrane, the polymer must have a high water permeability, yet a low permeability for the salts. To maximise efficiency, the membrane area must be large and its thickness as small as possible consistent with a lack of pinholes. A high pressure is applied to the salt water side of the membrane. Because it is thin, a cellulose triacetate membrane is supported on a porous cellulose nitrate-cellulose acetate support structure to resist the pressure. To make the unit compact the composite membrane is spirally wound on to an inner cylinder, and the edges glued together. When a pressure of 70 bar is applied to the seawater side, NaCl rejection levels in excess of 99.7% can be achieved. 

Riggs, J. A. and Smith, B.D. 1997. Facilitated transportof small carbohydrates through plasticized cellulose triacetate membranes. Evidence for fixed-site jumping transport mechanism. Journal of the American Chemical Society 119 2765-2766. 

White, K. M., Smith, B. D., Duggan, P. J., Sheahan, S. L., and Tyndall, E. M. 2001. Mechanism of facilitated saccharide transport through plasticized cellulose triacetate membranes. Journal of Membrane Science 194 165-175. 

Bayou, N., Arous, O., Amara, M., and Kerdjoudj, H. 2010. Elaboration and characterisation of a plasticized cellulose triacetate membrane containing trioctylphosphine oxide (TOPO) Application to the transport of uranium and molybdenum ions. Comptes Rendus Chimie 13 1370-1376. 

In cellulose acetate, sometimes called cellulose di acetate, approximately 75% of hydroxyl groups on the backbone of the polymer are replaced with acetate group typically by treating cellulose with acetic acid. It consists of two acetate radicals on each unit of d-anhydroglucopyranose of the cellulose molecule, first prepared in 1885. Production of cellulose triacetate membranes involves complete hydroxyl group substitution (at least 92% of the hydroxyl groups were acetylated). The complete substitution results in... 

Villalobos-Rodriguez, R., Montero-Cabrera, M.E., Esparza-Ponce, H.E., Herrera-Peraza, E.F Ballinas-Casarrubias, M.L. (2012) Uranium removal from water using cellulose triacetate membranes added with activated carbon. Applied Radiation and Isotopes, 70,872-881. 

C. Pan, Permeation of water vapor through cellulose triacetate membranes in hollow fiber form, J. Appl. Polym. Sci., 1978, 22, 2307-2323. 

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