Carbon Capillary Membranes

They also formed the condensed polynuclear aromatic (COPNA) resin film on a porous a-alumina support tube. Next, a pinhole-free CMSM was produced by carbonization at 400-1,000°C [29], The mesopores of the COPNA-based caibon membranes did not penetrate through the total thickness of each membrane and served as channels which increased permeances by linking the micropores. CMSMs produced using COPNA and BPDA-pp ODA polyimdes showed similar permeation properties even though they had different pore stractures. This suggests that the micropores are responsible for the permselectivities of the carbonized membrane. Besides that, Fuertes [30] used phenohc resin in conjunction with the dip coating technique to prepare adsorption-selective carbon membrane supported on ceramic tubular membranes. 

There are other different coating methods on porous stainless steel support media in the production of carbon membranes supported on tube including bmsh coating spray-coating and nltrasonic deposition of the polymer resin. For example, Shiflett and Foley reported varions approaches to prepare carbon molecular sieve layers on the stainless steel snpportby nltrasonic deposition [31]. 

Alternatively, Wang et al. [32] nsed a gas phase coating technique, vapor deposition polymerization (VDP) to prepare snpported carbon membranes from furfuiyl alcohol. They reported that the membranes prepared by VDP had comparable CH selectivities to bnt lower CO2 permeabilities than certain PFA-based membranes prepared by dip-coating techniqnes. 

Asymmetric capillary CMSMs were prepared using Kapton PI and their gas permeation properties reported by Haraya et al. [33], Capillaiy CMSM must have a controlled asymmetric stmctnre, consisting of a dense surface layer with molecular 

Petersen et al. prepared CMSMs (capillary tubes) by using a precursor derived from Kapton [34]. An integral asyrrrmetric capillary carbon membrane was prepared by coagulation of a PAA solution which was imidized to a Kapton capillary arrd firrally pyrolyzed to a capillary carbon membrane. 

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Table 3.1 summarizes the configurations of carbon membranes found in the ht-erature. It is noticed that most of the carbon membranes produced from the 1980s to early the 1990s are flat disk or flat sheet membranes. Only in the middle of the 1990s, carbon membranes supported on tubes were fabricated, followed by carbon capillary membranes and carbon hollow fiber membranes. Flat sheet carbon membranes are more suitable for laboratory or research applications while carbon membranes supported on tube, carbon capillary membranes and carbon hollow fiber membranes are more practical and suitable to apply in industry. 

More sophisticated techniques than the ones used by Haldane have estabhshed that CO binds to hemoglobin with an affinity 200 times greater than that of oxygen (Ernst and Zibrak, 1998 Roughton and Darling, 1944 Sendroy et al, 1930). Carbon monoxide diffuses from the alveoh to the blood in pulmonary capillaries across the alveoh-capillary membrane, which is composed of pulmonary epithelium, the capillary epithelium, and the fused basement membranes of the two. The uptake of CO by Hb is very rapid and the transfer of CO is diffusion limited (Prockop and Chichkoa, 2007). 

FIGURE 13.14 Schematic diagrams of facilitated transport of gas using capillary membrane module for removal and enrichment of carbon dioxide, (a) Experimental capillary membrane apparatus and (b) capillary membrane modules with permeation of carrier solution. (From Teramoto, M., Ohnishi, N., Takeuchi, N., et al., Sep. Purif TechnoL, 30, 215, 2003. With permission.)... 

Carbon dioxide separation from the air, mixtures with CH4, N2, O2, has been studied from both biological and engineering applications. Spiral-type FLM, HFLM, and capillary membrane techniques were tested for these purposes. 

Teramoto M, Ohnishi N, Takeuchi N, Kitada S, Matsuyama H, Matsumiya N, and Mano H. Separation and enrichment of carbon dioxide by capillary membrane module with permeation of carrier solution. Separ Purif Technol, 2003 30(3) 215-227. 

Air is inhaled during respiration and passes through the upper respiratory tract and to the alveoli capillary membrane in the lower respiratory tract. The lower respiratory tract is the site of gas exchange. Oxygen attaches to hemoglobin in blood. Carbon dioxide leaves the blood and is expelled through the lower and upper respiratory tracts during expiration. 

The diffusing capacity of the lung for carbon monoxide (CO) is a measure of the ability of the alveolar capillary membrane to transfer or conduct gases from the alveoli to the blood. This transport process is entirely a passive one brought about by diffusion. As described previously in Section 2.2, the barriers for diffusion consist of surfactant, alveolar epithelium, interstitital fluid, capillary endothelium, plasma, and the red blood cell membrane. 

The helium is inert and insoluble in lung tissue and blood, and equilibrates quickly in unobstructed patients, indicating the dilution level of the test gas. Acetylene, on the other hand, is soluble in blood and is used to determine the blood flow through the pulmonary capillaries. Carbon monoxide is bound very tightly to hemoglobin and is used to obtain diffusing capacity at a constant pressure gradient across the alveolar-capillary membrane. 

A concept for a methanol (or ethanol) fuel processor based upon steam reforming and membrane separation was presented by Gepert et td. [400]. As shown in Figure 5.33, the alcohol/water mixture was evaporated and converted by steam reforming in a fixed-bed catalyst, into which palladium capillary membranes were inserted. The retenate then entered the combustion zone, which was positioned concentrically around the reformer bed at the reactor wall. Air was fed into the combustion zone and residual hydrogen, carbon monoxide and unconverted methanol combusted therein. The sealing of the membranes at the reactor top was an issue solved by air-cooled elastomers. 

Haraya K, Suda H, Yanagishita H, Matsuda S (1995) Asymmetric capillary membrane of a carbon molecular sieve. J Chem Soc Chem Commun 1781-1782... 

K. Haraya, H. Snda, H. Yanagishita, S. Matsuda, Asymmetric capillary membrane of a carbon molecnlar sieve, / Chem. Soc., Chem. Commun.y 1995, 17, 1781-1782. 

Bone is a porous tissue composite material containing a fluid phase, a calcified bone mineral, hydroxyapatite (HA), and organic components (mainly, collagen type). The variety of cellular and noncellular components consist of approximately 69% organic and 22% inorganic material and 9% water. The principal constiments of bone tissue are calcium (Ca ), phosphate (PO ), and hydroxyl (OH ) ions and calcium carbonate. There are smaller quantities of sodium, magnesium, and fluoride. The major compound, HA, has the formula Caio(P04)g(OH)2 in its unit cell. The porosity of bone includes membrane-lined capillary blood vessels, which function to transport nutrients and ions in bone, canaliculi, and the lacunae occupied in vivo by bone cells (osteoblasts), and the micropores present in the matrix. 

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