Tubular cellulose acetate membranes

Figure 1.4 Capped, in-floor immersion tank located at Boelter Hall that was used by Loeb and Sourirajan to cast tubular cellulose acetate membranes at UCLA, as viewed in 2008.

The first commercial brackish water RO(BWRO) was on line at the Raintree facility in Coalinga, California. Tubular cellulose acetate membranes developed and prepared at UCLA were used in the facility. Additionally, the hardware for the system was fabricated at UCLA and transported piecemeal to the facility.9... 

Parkin, M.F. and Marshall, K.R., "The Cleaning of Tubular Cellulose Acetate Ultrafiltration Membranes", N.Z. Journ. 

Cellulose acetate membranes were originally cast in tubular form (refer to Figure 1.3). These tubular membranes were used in... 

Song, K. M. and Hong, W. H. 1997. Dehydration of ethanol and isopropanol using tubular type cellulose acetate membrane with ceramic support in pervaporation process. J. Membr. Sci. 123 27-33. 

In this type of module a number of membranes of tubular shape are encased in a container. For example, 18 tubes are connected in scries by headers at both ends of the Nitto NTR-1500-PI 8A module. Figures 7.9 and 7.10 show the structure of the module. Cellulose acetate membranes are formed in the internal wall of the support tube of 12-mm internal diameter The tubular membranes so prepared are inserted into plastic tubes with many holes, which are mounted in a module container. The feed liquid flows inside the tube, and the permeate flows from the inside to the outside of the membrane tube and is collected at the permeate outlet. There are also tubular modules in which the feed is supplied to the outside of the membrane tube. The main features of the tubular module are... 

A decade after Dr. Hassler s efforts, Sidney Loeb and Srinivasa Sourirajan at UCLA attempted an approach to osmosis and reverse osmosis that differed from that of Dr. Hassler. Iheir approach consisted of pressurizing a solution directly against a flat, plastic film. Their work led to the development of the first asymmetric cellulose acetate membrane in 1960 (see Chapter 4.2.1). This membrane made RO a commercial viability due to the significantly improved flux, which was 10 times that of other known membrane materials at the time (such as Reid and Breton s membranes). These membranes were first cast by hand as flat sheets. Continued development in this area led to casting of tubular membranes. Figure 1.3 is a schematic of the tubular casting equipment used by Loeb and Sourirajan. Figure 1.4 shows the capped, in-floor immersion well that was used by Loeb and students and is still located in Boelter Hall at UCLA. 

Cellulose acetate membranes were originally cast in tubular form (refer to Figure 1.3). These tubular membranes were used in the first commercial RO system at Coalinga, California in 1965. The membranes were developed and prepared at UCTA (see Chapter 1). The break for commercial viability came when as an appropriate swelling agent, formamide, was found for the cellulose acetate membrane during preparation. ... 

Like evaporators, RO works on most plating baths and rinse tanks. Most RO systems consist of a housing that contains a membrane and feed pump. There are four basic membrane designs plate-and-frame, spiral-wound, tubular, and hollow-fiber. The most common types of membrane materials are cellulose acetate, polyether/amide, and polysulfones.29... 

Salts rejected by the membrane stay in the concentrating stream but are continuously disposed from the membrane module by fresh feed to maintain the separation. Continuous removal of the permeate product enables the production of freshwater. RO membrane-building materials are usually polymers, such as cellulose acetates, polyamides or polyimides. The membranes are semipermeable, made of thin 30-200 nanometer thick layers adhering to a thicker porous support layer. Several types exist, such as symmetric, asymmetric, and thin-film composite membranes, depending on the membrane structure. They are usually built as envelopes made of pairs of long sheets separated by spacers, and are spirally wound around the product tube. In some cases, tubular, capillary, and even hollow-fiber membranes are used. 

Membranes are typically made of cellulose acetate or aromatic polyamides because of their high permeability to water and low permeability to salts. They are normally produced in tubular or spiral-wound modules, which are then packed inside a reaction vessel. Their fouling can be minimized by either pretreating the influent streams or diluting them with the clean water produced. 

Brodie crystallizer-purifier, 545, 547 Kureha purifier, 545,547 multistage, 543 MWB process, 543,545 Phillips process, 544-546 Schilaknecnt column, 543,544,546 TNO bouncing ball process 545.547 Melt purification. See Melt crystallization Membranes, 631,632,641 applications, 632 cellulose acetate, 635 equipment configurations, 632 gas permeation,633,644 hollow fiber, 632,633,641,643 performance, 646 Permasep, 641 olate and frame, 638 Prism, 633,643 properties, 635,636 structures, 632 tubular, 638,639 types, 635, 636... 

The first composite reverse osmosis membrane reported in the technical literature was developed by Peter Francis of North Star Research Institute in 1964 (4). This membrane was formed by float-casting an ultrathin film of cellulose acetate (CA) upon a water surface, removing the membrane from the water surface by lamination onto a pre-formed microporous support film and drying to bond the membrane to the support. This float-casting procedure has since been described in the technical literature for both flat sheet and tubular membranes ( 5, 6, T). 

TWO kinds of cellulose acetate ultrafiltration tubular membranes (T2/A and T4/A) produced by Paterson Candy International, Limited, England, were employed in this study. Six kinds of solutes, polyethylene glycol (PEG//4000), vitamin B12, raffinose, sucrose, glucose, and glycerin, were used. Molecular weights, diffusivities and molecular radii of these solutes are shown in Table 1. The experimental apparatus is shown schematically in Fig. 7. 

Ultraflltraiion membranes are commonly asymmetric (skinned) polymeric membranes prepared by the phase inversion process. Materials commercially made into membranes include cellulose nitrate, cellulose acetate, polysulfone. aramids, polyvinylidene fluoride, and nctylonitrile polymers and copolymers. Inorganic meni-braues of hydrous zirconium oxide deposited on a tubular carbon backing are also commercially available. 

Applications for FT-30 membrane have appeared in all reverse osmosis fields from seawater desalination to home tapwater systems operating on line pressure. At this date, it is the only commercial reverse osmosis membrane other than cellulose acetate that has specific FDA approval for food contact usage.63 Versions of this membrane, manufactured under license to FilmTec, are available in tubular form (ZF-99, Patterson Candy International) and plate-and-frame design (HR-95, HR-98, De Danske Sukkerfabrikker).64 65... 

Wu et al. (1992) treated the surfaces of the hydrophilic porous membranes, such as cellulose acetate, by radiation graft polymerization of styrene to increase their hydrophobicity and to reach the MD membrane characteristics. Kong et al. (1992) employed a cellulose nitrate membrane modified via plasma polymerization of both vinyltrimethylsilicone and carbontetrafluoride and octafluorocyclobutane for the preparation of MD membranes. Fujii et al. (1992) prepared tubular membranes from PVDF polymer dopes by using the dry-jet wet-spinning technique. Ortiz de Zarate et al. (1995) and Tomaszewska (1996) reported on PVDF flat-sheet membranes prepared for MD by the phase inversion method. 

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