Membranes preparation

Other Asymmetric Membrane Preparation Techniques. A number of other methods of preparing membranes have been reported i the literature and are used on a small scale. Table 1 provides a brief summary of these techniques. 

Chloromethylation was also carried out to modify the polysulfone for preparing membrane materials.171... 

As an electrolyte, Nafion 112 (Du Pont, Inc) membrane was pretreated using H2O2, H2SO4 and deionized water before ion beam bombardment. The prepared membranes with a size of 8 X 8 cm were mounted on a bombardment frame with a window size of 5 x 5 cm, equal to the active area of the test fuel cells, and dried up at 80 C for 2 hr. Then, the mounted membrane was brought in a vacuum chamber equipped with a hollow cathode ion beam source as described in the previous study [1]. Ion dose was measured using a Faraday cup. Ion density... 

The obtained results show that the prepared membranes are methanol selective, but the performance of these membranes (separation factor=30, for PVA/Pacr.Ac.=80/20, 5 wt% methanol in the feed, 25 °C) is lower than those reported by J.W. Rhim and Y.K. Kim [75] (separation factor 1250 for PVA/Pacr.Ac.=75/25, 20 wt% methanol in the feed, 30 °C). 

The electroless plating method described above was used to prepare membranes that contain cylindrical gold nanotubules, which span the complete thickness of the membrane. As before, polycarbonate filtration membranes with cylindrical, monodisperse pores (Poretics, 6 [im thick, pore dia. = 30 nm) were used as the templates. The inside diameter (i.d.) of the nanotubules can be varied by varying the plating time (Fig. 14). At sufficiently long plating times, Au nanotubules with i.d.s of molecular dimensions (<1 nm) are obtained [106],... 

Another possible solution to the problem of analyzing multiple-layered membrane composites is a newly developed method using NMR spin-lattice relaxation measurements (Glaves 1989). In this method, which allows a wide range of pore sizes to be studied (from less than 1 nm to greater than 10 microns), the moisture content of the composite membrane is controlled so that the fine pores in the membrane film of a two-layered composite are saturated with water, but only a small quantity of adsorbed water is present in the large pores of the support. It has been found that the spin-lattice relaxation decay time of a fluid (such as water) in a pore is shorter than that for the same fluid in the bulk. From the relaxation data the pore volume distribution can be calculated. Thus, the NMR spin-lattice relaxation data of a properly prepared membrane composite sample can be used to derive the pore size distribution that conventional pore structure analysis techniques... 

FIGURE 3.10 Photomicrobiocidal activity of the reinforced zinc phthalocyanide/chit-osan membrane on E. coli suspensions in log survival scale. , freshly prepared membrane , the same membrane after 9 months (Bonnett et al, 2006). 

In medical applications, the dialysis SPM may be the patient s own stomach lining. A prepared solution is infused into the abdomen, stimulating osmotic flow of toxins across the stomach lining into the ingested solution, which is subsequently drained from the stomach. Alternatively, the dialyzer for blood dialysis (hemodialysis) may be a prepared membrane with special solution over which the blood flows to osmotically remove impurities. 

Ultrafiltration has been used in fractionating dextrans,244 By use of specially prepared membranes,246 it should be possible to extend this simple, gentle method to effect fractionation of polyglycoses and polysaccharides in general. Gel filtration also permits passage of macromolecules on the basis of their molecular size, and this method has proved useful in the fractionation of dextrans246 and dextrins.247 The ease and capacity of this method should make it valuable in the fractionation of polyglycoses. 

The ceramic and zeolite membranes described above have been shown to have exceptional selectivities for a number of important separations. However, the membranes are not easy to make and consequently are prohibitively expensive for many separations. One solution to this problem is to prepare membranes from materials consisting of zeolite particles dispersed in a polymer matrix. These membranes are expected to combine the selectivity of zeolite membranes with the low cost and ease of manufacture of polymer membranes. Such membranes are called mixed-matrix membranes. 

Kinoshita et alJ107,l0x used poly(L-glutamic acid) containing 12-14 mol% azobenzene units in the side chains (Scheme 3, Structure III) to prepare membranes obtained by coating a porous Millipore filter with a 0.2 % chloroform solution of III. Irradiation at 350 nm was found to increase the membrane potential and crossmembrane permeability. The photoinduced alterations of the membrane functions were completely reversible and could be controlled by irradiation and dark-adaptation, in correlation with the trans-cis photoisomerization of the azobenzene units. 

By far the majority of polymeric membranes, including UF membranes and porous supports for RO, NF or PV composite membranes, are produced via phase separation. The TIPS process is typically used to prepare membranes with a macroporous barrier, that is, for MF, or as support for liquid membranes and as gas-liquid contactors. In technical manufacturing, the NIPS process is most frequently applied, and membranes with anisotropic cross-section are obtained. Often,... 

Macheras JT, Bikson B, Nelson JK. Method of preparing membranes from blends of polymers. Eur Patent Application (EP 706819 A2 960417) 9 pp... 

To obtain quantitative data about the integrity of the prepared membranes, both permeance and selectivity measurements were performed. It was found that high quality flat membranes... 

It was tried to make membranes using the specifications obtained in the technical economic evaluation. Of main importance besides the economic considerations was of course the stability of the membrane under steam reforming conditions. To test the stability of the prepared membranes, so-called Simulated Ambient Steam Reforming (SASRA) conditions were used. 

Ionomers are used to prepare membranes for a variety of applications including dialysis, reverse osmosis, and in electrolytic cells for the chlor-alkali industry. This latter application needs materials that show good chemical resistance and ionomers based on perfluorinated backbones with minor amounts of sulfonic or carboxylic acids are ideal. They also show good ion-exchange properties. 

The aspect of hole filling by plasma deposition can be demonstrated by the transport characteristics of LCVD-prepared membranes. First, the porosity as porous media calculated from the gas permeability dependence on the applied pressure can be correlated to the salt rejection of the composite membrane as shown in Figure 34.13. The effective porosity s/, where s is the porosity and q is the tortuosity factor, is measured in dry state and may not directly correlate to the porosity of the membranes in wet state. The effective porosity of LCVD-prepared membranes was measured before the reverse osmosis experiment. The decrease of porosity (as porous media) is clearly reflected in the increase in salt rejection in reverse osmosis. 

Figure 2 A flow chart that outlines the general strategies in preparing membrane proteins for structural studies.

Filtration experiments were carried out using this prepared membrane in a cross-flow apparatus, which was the same as the PWF measurement apparatus. PMMA particles (1000 mg-r, 0.8 pm in diameter) were used as model particle pollutants. When the PMMA solution was introduced by the feed magnet gear pump, the flux of the same object declined to a certain level. In this time, membranes needed regeneration, we used the technique of back washing. To cany out the back washing, we changed the flow direction by niddle valve and used pure water at a pressure of 2 kg cm for 1 minute. 

Figure 2 shows the SEM pictures of the prepared Membranes A, B, and C. Membrane D is also shown. It is obvious that Membranes A, B, and C have finer carbon whiskers, with diameters of approximately 0.6, 0.4, and 0.2 pm, respectively, while the whiskers of membrane D are larger, 2 pm (Li et al, 2001). As the SEM pictures show, after carbonization of polymer latex and CVD of methane, the novel membranes had thin and dense carbon whiskers compared with die conventional ones. 

As previously explained, it can be advantageons to generate extraporosity at a larger scale in the separative layer. The main condition that has to be respected is that the additional porosity mnst not be directly interconnected in order to preserve the entoff fixed by the porosity of the continuous phase. Templating by polystyrene latex was nsed to prodnee individnal macropores inside the silica layer (Figure 25.25). This route can be applied to prepare membranes of other oxides with varions possible strategies in terms of the synthesis process (Figure 25.26). In addition, the presence of dispersed micron-size or submicron-size... 

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