Membrane materials membranes

Membrane material Membrane configuration Operation mode Pore diameter (pm) Application Membrane producer References... 

Membrane designation Membrane material Membrane pore dia.orMWCO Water flux ) (L/hr-m ) (%)... 

Ref. Degumming Conditions Membrane Materials Membrane Module Residual Permeate Phosphorus Flux (LMH) Content(ppm) ... 

The development of an effective cleaning process has to take into account the nature of the foulants, the thermal and chemical resistance of the membrane material, membrane housing and seals. Typically, membrane manufacturers make specific recommendations regarding the cleaning agents and cleaning procedures that need to be used for different membranes and applications. 

Some of the many different types of catalysts which have good catalytic properties for the OCM reaction qualify as membrane materials. Membrane reactors for OCM were designed and tested by Nozaki et al. (1992). Three kinds of reactors were developed the first one consisted of a porous membrane covered with a thin film of catalyst (type I) the second one, a dense ionic-conducting membrane (non porous) with catalytic layer (type II) and the third one was a membrane made of perovskite-type mixed oxides which was active for OCM (type III). Figure 11 presents the diagram for the membrane reactor system and table 13 shows the different materials used for supports and coated catalysts. 

After a brief description of membrane materials, membrane rejection and fouling will be addressed. Both rejection of and fouling ly natural organics and inorganic colloids, will be a major focus of this work. A further issue is the characterisation of clean andfouled membranes as well as fouling control. 

Ref. Reaction Membrane material Membrane type Membrane area [m ] Temp. rq... 

Ml EC membrane material Membrane type Membrane wall thickness (mm) Temperature (°C) Flux ybj (ml(STP)/cm /min) Sweep gas flow Reference rate (cm /min) ... 

MIEC membrane material Membrane type Flux (ml/cmVmin) Temperature t C) Reference... 

The focus is on the properties of the inorganic membrane material. Membrane shows a very high selectivity and good stability. 

Vendor Membrane material Membrane length (mm) Membrane diameter (mm) Molecular weight cutoff (kDa)... 

Membrane Material Membrane Form Snrface Affinity Mean Pore Size Effective Membrane Area Authors... 

Membrane Material Membrane Morphology Configuration Examples of Membrane and Module, Membrane Suppliers... 

Membrane Nominal Cut of Molecular Weight Nominal Pore Size ( xm) Membrane Materials Membrane Shape Membrane Preparation Process... 

Name Membrane Material Membrane Diameter (mm) MWCO Availability (kDa) Manufacturer... 

Name Membrane Material Membrane Module Type Membrane Area (m ) Pore Size (nm) LRV Rating with Test Virus Manufacturer... 

First, we consider the experimental aspects of osmometry. The semiperme-able membrane is the basis for an osmotic pressure experiment and is probably its most troublesome feature in practice. The membrane material must display the required selectivity in permeability-passing solvent and retaining solute-but a membrane that works for one system may not work for another. A wide variety of materials have been used as membranes, with cellophane, poly (vinyl alcohol), polyurethanes, and various animal membranes as typical examples. The membrane must be thin enough for the solvent to pass at a reasonable rate, yet sturdy enough to withstand the pressure difference which can be... 

Validation Considerations. Mechanisms other then size exclusion maybe operative ia the removal of vimses from biological fluids. Thus vims removal must be vaUdated within the parameters set forth for the production process and usiag membrane material representative of the product line of the filter. 

Nonporous Dense Membranes. Nonporous, dense membranes consist of a dense film through which permeants are transported by diffusion under the driving force of a pressure, concentration, or electrical potential gradient. The separation of various components of a solution is related directiy to their relative transport rate within the membrane, which is determined by their diffusivity and solubiUty ia the membrane material. An important property of nonporous, dense membranes is that even permeants of similar size may be separated when their concentration ia the membrane material (ie, their solubiUty) differs significantly. Most gas separation, pervaporation, and reverse osmosis membranes use dense membranes to perform the separation. However, these membranes usually have an asymmetric stmcture to improve the flux. 

Ceramic, Metal, and Liquid Membranes. The discussion so far implies that membrane materials are organic polymers and, in fact, the vast majority of membranes used commercially are polymer based. However, interest in membranes formed from less conventional materials has increased. Ceramic membranes, a special class of microporous membranes, are being used in ultrafHtration and microfiltration appHcations, for which solvent resistance and thermal stabHity are required. Dense metal membranes, particularly palladium membranes, are being considered for the separation of hydrogen from gas mixtures, and supported or emulsified Hquid films are being developed for coupled and facHitated transport processes. 

Dense Symmetrical Membranes. These membranes are used on a large scale ia packagiag appHcations (see Eilms and sheeting Packaging materials). They are also used widely ia the laboratory to characterize membrane separation properties. However, it is difficult to make mechanically strong and defect-free symmetrical membranes thinner than 20 p.m, so the flux is low, and these membranes are rarely used in separation processes. Eor laboratory work, the membranes are prepared by solution casting or by melt pressing. 

A third factor is the ease with which various membrane materials can be fabricated into a particular module design. Almost ah membranes can be formed into plate-and-frame, spiral, and tubular modules, but many membrane materials caimot be fabricated into hollow-fine fibers or capihary fibers. Finahy, the suitabiHty of the module design for high pressure operation and the relative magnitude of pressure drops on the feed and permeate sides of the membrane can sometimes be important considerations. 

Pervaporation operates under constraints similar to low pressure gas-separation. Pressure drops on the permeate side of the membrane must be small, and many prevaporation membrane materials are mbbery. For this reason, spiral-wound modules and plate-and-frame systems ate both in use. 

Permeability P, can be expressed as the product of two terms. One, the diffusion coefficient, reflects the mobility of the individual molecules in the membrane material the other, the Henry s law sorption coefficient, reflects the number of molecules dissolved in the membrane material. Thus equation 9 can also be written as equation 10. 

FoUowiag Monsanto s success, several companies produced membrane systems to treat natural gas streams, particularly the separation of carbon dioxide from methane. The goal is to produce a stream containing less than 2% carbon dioxide to be sent to the national pipeline and a permeate enriched ia carbon dioxide to be flared or reinjected into the ground. CeUulose acetate is the most widely used membrane material for this separation, but because its carbon dioxide—methane selectivity is only 15—20, two-stage systems are often required to achieve a sufficient separation. The membrane process is generally best suited to relatively small streams, but the economics have slowly improved over the years and more than 100 natural gas treatment plants have been installed. 

Reverse osmosis membrane separations are governed by the properties of the membrane used in the process. These properties depend on the chemical nature of the membrane material, which is almost always a polymer, as well as its physical stmcture. Properties for the ideal RO membrane include low cost, resistance to chemical and microbial attack, mechanical and stmctural stabiHty over long operating periods and wide temperature ranges, and the desired separation characteristics for each particular system. However, few membranes satisfy all these criteria and so compromises must be made to select the best RO membrane available for each appHcation. Excellent discussions of RO membrane materials, preparation methods, and stmctures are available (8,13,16-21). 

Developments and advances in both membrane materials and reverse osmosis modules have increased the range of appHcations to which RO can be apphed. Whereas the RO industry has developed around water desalination (9,53,73,74), RO has become a significant cornerstone in other industries. 

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

Table 1. Simplified Hot Applied Membrane Material Specifications...

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