Membranes filled

Another method used for nitrate determination on dried and milled herbage employs the nitrate selective electrode. One of the first published methods was that of Paul and Carlson (1968). Other anions, especially chloride, can interfere. These authors removed chloride with silver resin, but Barker ef al. (1971) omitted the resin because it tended to foul the electrode and cause excessive drift. Normally the Cl N03 ratio is so low as not to interfere, but saline precipitation from coastal plots could affect this. The method was further modified to allow storage of extracts for up to 64 h by adding a preservative of phenyl-mercuric acetate and dioxane, both very toxic (Baker and Smith, 1969). This paper mentions the need to change the electrode s membrane, filling solution and liquid ion exchanger every 2 months to minimize chloride interference. It is easy to overlook electrode maintenance between batches of nitrate analyses, and this can lead to errors and sluggish performance. 

J. Marchese, M. Anson, N. Ochoa, P. Pradanos, L. Palacio, and A. Hernandez, Morphology and structure of ABS membranes filled with two different activated carbons, Chem. Eng. Sci., 61(16) 5448-5454, August 2006. 

An open beaker of pure water, under ordinary atmospheric pressure, contains a glass tube to which is attached a semipermeable membrane filled with an aqueous solution of, for example, sugar (or salt or other solute of low volatility). As its name implies, the membrane... 

Another phase boundary potential is developed at the inner surface of the membrane (at the membrane/filling solution interface). The membrane potential corresponds to the potential difference across the membrane ... 

Polymeric membranes are proposed to be used to reduce the SO2 concentration in the waste gas of a sulfuric acid plant from 1.5% to 0.01%. Hollows fibers (made of polymeric membrane) fill the separations unit. The waste gas containing 1.5% SO2 is the fresh feed in the amount of 1000 m3 hr at 25°C and 1 atm (101.3 kPa). To meet the product gas specifications, part of the product stream has to be recycled to reduce the concentration of SO2 entering the separator itself to 1.10% SO2 in G, the process feed. The process is isothermal at 25°C and isobaric at 1 atm. 

The osmotic pressure of solutions are discussed here as an introduction to the concept of osmotic pressme in suspension [21]. The phenomena of osmotic pressure is illustrated by a semipermeable membrane filled with a sugar solution immersed in water. The pressure inside the membrane, p + it, is large than that in the water, p, according to the formula... 

For polymeric membranes filled with absorptive fillers, sorption in the filler occurs in accordance with the Langmuir adsorption isotherm while Henry s law governs that in the polymer matrix. This kind of sorption isotherm is designated as type-II isotherm. 

Chen HL, Wu LG, Tan J, and Zhu CL. Polyvinyl alcohol membrane filled 3-cyclodextrin for separation of isomeric xylenes by... 

FIGURE 27.67 Conductivity as a function of relative humidity for (a) a high-molecular-weight s-PEK membrane (FuMA-Tech thickness 50 xm) and (h) the same membrane filled with 35 wt% of Zr(03P-0H)(03P-C6H4S03H)-nH20. (Reprinted from Alberti, G. and Casciola, M., Annu. Rev. Mater. Res., 33, 129, 2003, copyright 2003 by Annual Reviews www.annualreviews.org. With permission.)... 

Fig. 12.25. Permeate flux versus tangential fluid velocity with a gelatine solution (10 g F, Ap = 1.5 bar) using a tubular alumina membrane filled with a fluidized bed.

Water can be removed from methanol by a membrane of polyvinyl alcohol cross-linked with polyacrylic acid, with a separation factor of 465.204 A polymeric hydrazone of 2,6-pyridinedialdehyde has been used to dehydrate azeotropes of water with n- and /-propyl alcohol, s- and tort butyl alcohol, and tetrahydrofuran.205 The Clostridium acetobutylicum which is used to produce 1-butanol, is inhibited by it. Pervaporation through a poly(dimethyl-siloxane) membrane filled with cyclodextrins, zeolites, or oleyl alcohol kept the concentration in the broth lower than 1% and removed the inhibition.206 Acetic acid can be dehydrated with separation factors of 807 for poly(4-methyl-l-pentene) grafted with 4-vinylpyridine,207 150 for polyvinyl alcohol cross-linked with glutaraldehyde,208 more than 1300 for a doped polyaniline film (4.1 g/m2h),209 125 for a nylon-polyacrylic acid membrane (5400 g/m2h), and 72 for a polysulfone.210 Pyridine can be dehydrated with a membrane of a copolymer of acrylonitrile and 4-styrenesulfonic acid to give more than 99% pyridine.211 A hydrophobic silicone rubber membrane removes acetone selectively from water. A hydrophilic cross-linked polyvinyl alcohol membrane removes water selectively from acetone. Both are more selective than distillation.212... 

S.Solfataricus contains enzymes of industrial interest, such as B-galactosidase and malic enzymes, for example. Artificial membranes filled with S.Solfataricus have been prepared by several methods. Cellulose acetate and poly-... 

In Eig. 2.12, the principle of compression sealing of membranes with a tubular configuration is depicted. The membrane tube is mounted in a metal end-cap and the space in between end-cap and membrane filled by the sealing material. Compressive forces are obtained upon increasing the temperature and the magnitude of these forces can be tuned by proper selection of the metal type and sealing material, based... 

Place each array membrane into a hybridization bottle. To wet the membranes, fill each hybridization bottle with 50 ml distilled H2O (DNase, RNase free). Then, carefully decant the water. 

HETEROGENEOUS MEMBRANES FILLED WITH HYPERCROSSLINKED POLYSTYRENE... 

Discussion. The method and technique used for fabrication of the aqueous liquid membranes are very important in achieving good stability. Membranes filled by condensation methods are much more stable than those which are soaked and allowed to dxy. One possible reason for this may be that the condensation method avoids the problem of ovofilling and thus ensures good curvature at the pore opeiungs. 

PPE membranes filled with silica and silane-modihed siUca nanoparticles can be used for the pervaporation separation of methanol MTBE mixtures. In comparison to an unfilled PPE membrane, the hlled membranes exhibit higher methanol selectivity and lower permeability. ... 

A study of the pervaporation separation of ethanol/water mixtures by polydimethylsiloxane (PDMS) membranes filled with phosphazene nanotubes showed selectivity favoring water over ethanol, which corresponds to the behavior of the host polymer. The nanotubes were reported to increase permeation flux and selectivity. This conclusion was further supported by the use of a TFE/phenoxy/2-allylphenoxy phosphazene host in place of PDMS. Phosphazenes also can be used as a cross-linker for traditional organic polymers to impart greater performance in the separation of water and ethanol. In this work, poly(vinyl alcohol) membranes were cross-linked with cyclotriphosphazene substituted with 4-hydroxybenzaldehyde... 

The company W.L. Gore Associates (EUcton, MD) develops membranes under the name Gore-Select consisting of a microporous stretched PTFE (expanded PTFE porous sheet) membrane filled with perfluorinated ionomer. The micro-porous PTFE matrix provides the mechanical strength, and... 

Fig. 8 Comparison of conductivity at 80-140 °C of Nafion (open symbols) and Nafion -ZrP membranes (filled symbols). Reprinted from [74]. (2004), with permission from Elsevier...

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