Ultrafiltration carbon membranes

Propionic acid and its derivatives are used in food, perfume and plastic applications. Traditional processes for making this compound, however, have limited productivity due to the low growth rate of the propionic bacteria and the inhibitory effect of the acid on the fermentation. The cheese whey permeate can be an inexpensive source of propionic acid. Propionic acids can be produced by fermentation of sweet whey permeate in a stirred tank reactor with cells separated from the medium and recycled back to the reactor by an ultrafiltration Z1O2 membrane on a carbon support [Boyaval and Corre, 1987]. This arrangement reduces the propionic acid concentration and increases the... 

Direct deasphalting of petroleum residues. Ultrafiltration zirconia membranes with a pore diameter of 6.3 nm on carbon support have been used to remove asphaltenes from a long residue at a temperature of 150X [Guizard et al., 1994]. With a higher than normal... 

Tremendous opportunity exists for hybrid processes consisting solely of membrane processes or a combination of membrane and non-membrane processes. Of the large number of potential combinations, studies of several are reported in the literature including nanofiltration with reverse osmosis [99] nanofiltration with electrodialysis [100] ultrafiltration with nanofiltration and reverse osmosis [101] ultrafiltration with membrane distillation [102] nanofiltration with reverse osmosis and a microfiltration membrane-based sorbent [103] microfiltration with flotation [104] microfiltration and ultrafiltration with ozone and activated carbon adsorption [105] and membrane processes with photocatalysis [106-107]. Despite the activity in this area, a comprehensive approach to designing hybrid systems does not exist future work would benefit from the development of such a design framework. 

Thermal Insulation is by far the most Important present application of oxide fibers. Transition alumina fibers, e.g., eta-alumina fibers, are produced at Intermediate firing temperatures and are used as supports for catalysts and Insulation tiles such as those used for the space shuttle orbiter [1-2]. Carbon fiber felts are used as internal thermal insulation for vacuum furnaces at extremely high temperatures. Activated carbon fibers, which are obtained by partial oxidation of selected carbon fibers, have extremely small pores and very high specific surface areas, ranging from 500 to 3000 mVg. They are of great interest in ultrafiltration as membranes for the treatment of used waters and liquids [3-5]. 

Gas permeation tests have been carried out for many carbon membranes. However, there is very limited data for the liquid permeation tests, especially for the application of carbon membranes for ultrafiltration (UF) or microfiltration (MF). Some studies [1,2] demonstrated that carbon UF membranes could be made by adding non-carbonizing polymers such as poly(ethylene glycol) (PEG) to the precursor solution. Encouraged by the findings of [3] and [4], Shah and co-woikers successfully made nanoporous carbon UF membranes suitable for bioprocessing applications [5]. 

Shah TN, Foley HC, Zydney AL (2007) Development and eharaeterization of nanoporous carbon membranes for protein ultrafiltration. J Membr Sci 295 (1-2) 40-49 Kim YY, Park HB, Lee YM (2004) Carbon molecular sieve membranes derived from thermally labile polymer containing blend polymers and their gas separation properties. J Membr Sci 243 (1-2) 9-14... 

Carbon membranes are still in their infancy as a technology, yet the promise they hold is enormous. Already we know that nanoporous (0.5-1.0 nm average pore size) carbon membranes show an especially high affinity for carbon dioxide transport, a property that will undoubtedly be of utility in carbon capture and sequestration. They are robust enough to withstand use in aqueous media and at either high or low pH. When engineered with mesopores (1.0-3.0 nm), they can be used to provide ultrafiltration of water and other process flttids. In combination with catalysts, they are able to combine reaction and separation, thereby providing a viable means to... 

Fuertes and Menendez (2002) and Centeno and Fuertes (1999, 2001) have published a series of studies using this precursor. Centeno and Fuertes (1999) have spin coated a small amount of a novolak-type phenolic resin on the surface of carbon supports. The membranes were then carbonized in a tubular furnace from 500 to 1000°C in vacuum. The resulting membranes had O2/N2 selectivity of around 10 and CO2/CH4 selectivity of 160. This work was later extended and in that case (Centeno and Fuertes, 2001 Fuertes and Menendez, 2002) a novalak-type phenolic resin was deposited on the inner face of a ceramic tubular membrane used for ultrafiltration. The membrane was subsequently pyro-lyzed to 700°C. In some cases an oxidative pretreatment was used before pyrolysis or an oxidative posttreatment after pyrolysis. The resulting membranes had O2 permeabilities around 100 Barrers and O2/N2 selectivities around 12 at 25°C. Films dip coated with resin three times had lower permeability and only slightly higher selectivities than those dipped only once. For hydrocarbon mixtures, the separation performance was increased by several treatments air oxidation of the resin, air oxidation of the carbon, or chemical vapor deposition (CVD) posttreatment of the carbon. 

M.S. Strano, A.L. Zydney, H. Barth, G. Wooler, H. Agarwal, H.C. Foley, Ultrafiltration membrane synthesis by nanoscale templating of porous carbon,/ Membrane Set, 2002,198,173-186. 

Pretreatment For most membrane applications, particularly for RO and NF, pretreatment of the feed is essential. If pretreatment is inadequate, success will be transient. For most applications, pretreatment is location specific. Well water is easier to treat than surface water and that is particularly true for sea wells. A reducing (anaerobic) environment is preferred. If heavy metals are present in the feed even in small amounts, they may catalyze membrane degradation. If surface sources are treated, chlorination followed by thorough dechlorination is required for high-performance membranes [Riley in Baker et al., op. cit., p. 5-29]. It is normal to adjust pH and add antisealants to prevent deposition of carbonates and siillates on the membrane. Iron can be a major problem, and equipment selection to avoid iron contamination is required. Freshly precipitated iron oxide fouls membranes and reqiiires an expensive cleaning procedure to remove. Humic acid is another foulant, and if it is present, conventional flocculation and filtration are normally used to remove it. The same treatment is appropriate for other colloidal materials. Ultrafiltration or microfiltration are excellent pretreatments, but in general they are... 

Another reaction performed in the dead-end reactor discussed before, is the allylic amination of 3-phenyl-2-propenyl-carbonic acid methyl ester with morpholine. [30] First and second generation commercially available DAB-dendrimers were functionalized with diphenylphosphine groups (Figure 4.13). Two different membranes were used, the Nadir UF-PA-5 (ultrafiltration) and the Koch MPF-50 (former SELRO) (nanofiltration), which gave retentions of 99.2% and 99.9% respectively for the second generation functionalized dendrimers. 

A significant recent advance has been the development of microfiltration and ultrafiltration membranes composed of inorganic oxide materials. These are presently produced by two main techniques (a) deposition of colloidal metal oxide on to a supporting material such as carbon, and (b) as purely ceramic materials by high temperature sintering of spray-dried oxide microspheres. Other innovative production techniques lead to the... 

Since membranes no longer had important nuclear applications in future, SPEC was sold in 1987 by the CEA to the French company Rhone-Poulenc which merged them with their polymeric membrane division to form the new subsidiary, currently known as Tech Sep. Zr02 based ultrafiltration membranes on 6 mm inner-diameter carbon tubes continues to be the main product line of Tech Sep in terms of inorganic membranes. 

Zirconia membranes on carbon supports were originally developed by Union Carbide. Ultrafiltration membranes are commercially available now under trade names like Ucarsep and Carbosep. Their outstanding quality is their high chemical resistance which allows steam sterilization and cleaning procedures in the pH range 0-14 at temperatures up to 80°C. These systems consist of a sintered carbon tube with an ultrafiltration layer of a metallic oxide, usually zirconia. Typical tube dimensions are 10 mm (outer diameter) with a wall thickness of 2 mm (Gerster and Veyre 1985). 

Davies (20) used powdered activated carbon in conjunction with ultrafiltration of activated sludge to adsorb soluble organic constituents which might otherwise pass through the membrane until the biomass can metabolize them. The reduction in effluent COD is shown in Figure 42. 

Ultrafiltration was applied to examine the size fractionation of Al, Ca, Cu, Fe, K, Na, and Pb in white and red wines [91]. Metal determinations were performed on the unfiltered wine, the 0.45 p,m membrane-filtered wine and each ultrafiltrate fraction. Aluminum was determined by ET-AAS, while FAAS was employed for Cu and Fe. An electroanalytical technique, stripping potentiometry, was selected for Pb measurement, whereas flame photometry was chosen for K and Na quantification. Fractionation patterns were evaluated and discussed. Castineira et al. [92] combined on-line tangential-flow multistage ultrafiltration with a home-built carbon analyzer and ICP-MS for size fractionation of nonvolatile dissolved organic compounds and metal species in three German white wines. The study showed that the major part of the elements investigated (up to 25) were dissolved in the size fraction of < 1 kDa, with the exception of Ba, Pb, and Sr, which also appeared in other fractions. 

Role of carbonic anhydrase in sodium When damaged by disease, the glomerular membranes allow tutHJte°n e thelial cells 0f renal plasma proteins to enter the glomerular ultrafiltrate. The loss of pro-... 

Adsorbents are used in medicine mainly for the treatment of acute poisoning, whereas other extracorporeal techniques based on physico-chemical principles, such as dialysis and ultrafiltration, currently have much wider clinical applications [1]. Nevertheless, there are medical conditions, such as acute inflammation, hepatic and multi-organ failure and sepsis, for which mortality rates have not improved in the last forty years. These conditions are usually associated with the presence of endotoxin - lipopolysaccharide (LPS) or inflammatory cytokines - molecules of peptide/protein nature [2]. Advantages of adsorption over other extracorporeal techniques include ability to adsorb high molecular mass (HMM) metabolites and toxins. Conventional adsorbents, however, have poor biocompatibility. They are used coated with a semipermeable membrane of a more biocompatible material to allow for a direct contact with blood. Respectively, ability of coated adsorbents to remove HMM solutes is dramatically reduced. In this paper, preliminary results on adsorption of LPS and one of the most common inflammatory cytokines, TNF-a, on uncoated porous polymers and activated carbons, are presented. The aim of this work is to estimate the potential of extracorporeal adsorption technique to remove these substances and to relate it to the porous structure of adsorbents. 

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