Membranes metallic

Metal-matrix composites Metal membranes Metal-metal bonds Metal naphthenates Metal oleates... 

Facilitated transport membranes can be used to separate gases membrane transport is then driven by a difference in the gas partial pressure across the membrane. Metal ions can also be selectively transported across a membrane driven by a flow of hydrogen or hydroxyl ions in the other direction. This process is sometimes called coupled transport. 

Poor adhesion of membrane to metal is the leading cause of failure in solid-state potentiometric sensors [116], For glass membranes, the mismatch of thermal coefficients of expansion between thin glass membrane and metal (mostly Pt) has been attributed to premature failure due to hairline crack formations in the glass layer [60], For polymer-based membranes, water vapor penetration was reported to compromise the membrane-metal interface, therefore affecting the sensor s performance. 

Another problem that is common for all membrane-based solid-state sensors is the ill-defined membrane-metal interface. A large exchange current density is required to produce a reversible interface for a stable potentiometric sensor response. One approach to improving this interface is to use conducting polymers. Conducting polymers are electroactive n-conjugated polymers with mixed ionic and electronic conductivity. They... 

A. thaliana AtNrampS belongs to a family of broad specificity membrane metal transporters and can complement deficiencies in manganese and iron transport in yeast (Thomine et al., 2000). It is expressed in both the roots and the aerial parts of plants, and is induced in roots by Fe starvation. Transgenic Arabidopsis plants over-expressing the gene under the control of the CaMV 35S promoter displayed Cd hypersensitivity and increased Fe accumulation, but the accumulation of Cd was not affected. 

The permeate solution metal ion concentration, M, >, does not appear in the flux equation, which means that the membrane metal ion flux is independent of the concentration of metal on the permeate side. However, the flux does depend on the concentration of metal ions, [M]0, on the feed solution side. At low values of [M]c, the flux will increase linearly with [M]c, but at higher concentrations the flux reaches a plateau value as the term [H]C/[M]aK becomes small compared to 1. At this point all of the available carrier molecules are complexed and no further increase in transport rate across the membrane is possible. The form of this dependence is illustrated for the feed and product solution metal ion concentrations in Figure 11.9. 

Ecoscope Hexane (organics) chelating resin (metals) Polyethylene membrane (organics), porous membrane (metals) Hydrophobic organic compounds, heavy metals Qualitative screening 2-4 weeks Direct injection of solvent or after concentration or extraction with acid 59... 

Whatever the ulitmate site(s) of action in the plant, the metals have to cross the plasma membrane of the root cells before reaching the intracellular compartment. Therefore, this barrier (including its associated transport systems) can be considered as the first target for metal action. Only after passing the membrane, metals can interact with other cellular components and processes. 

Tsukube 14) reported in 1984 a multi-armed cyclam (18) which has the ability to transport NH4+ cation through a chloroform layer (a so-called liquid membrane ). Metal ions such as K+ are not transported under similar conditions, a selectivity generally unobserved with the common crown ethers and cryptates. Since the transport rate decreases substantially when the furan rings terminating the pendant arms are... 

Hydrogen sulfide is typically found in well water that is devoid of oxygen. This compound easily oxidizes and releases elemental sulfur, which is very sticky and results in irreversible fouling of RO membranes. Metal sulfides can also form, which can precipitate. Deposits can be sooty-black or a pasty-gray.8 Fouling with elemental sulfur or metallic sulfides will cause a decrease if flux and an increase in salt passage. 

The first key element in the uptake of these two metal ions is that the substrate is the lower valent state species, Cu(I) in the case of copper and Fe(II) in the case of iron (Dancis et al., 1990, 1992 Hassett and Kosman, 1995 Kosman, 1993). Normally, these reduced valence species are provided by the action of plasma membrane metal reductases, an activity in yeast provided predominantly by the product of the FREl gene (Dancis et al., 1992). However, Fe(II) [or Cu(I)] provided exogenously to the cell is equally competent for uptake and, in most experimental regimes, is added directly or generated in situ by the addition of a strong reductant like ascorbate or dithionite. Cu(I) is the direct substrate for uptake, through the Ctrlp copper permease in most yeast strains (Dancis et al., 1994). However, the presence of Fe(II), although required, alone is not... 

Physicochemical Solid-state and ion-exchange membranes, metal oxides, solgels, zeolites, conducting poymers Doped semiconducting oxides, immobilised metals... 

P. Mercea, L. Muresan, V. Mecea, D. Silipas, and I. Ursu, Permeation of gases through poly(ethyleneterephthalate) membranes metallized with palladium, J, Membr, ScL i5 19 (1988). 

Most of the time, metal/dielectric nanocomposites are studied in the form of solutions or thin solid films on a substrate Colloids, doped and annealed glasses, sol-gels, surfactant-stabilized nanoparticles, micelles, two- or three-dimension self-assembled nanocomposites, self-organized mesoporous oxides filled with metals, electrochemically-loaded template membranes, metal-ion implanted crystals, nanocomposite films elaborated by laser ablation, cluster-beam deposition, radio-frequency sputtering, or nanolithography. 

A sol of metal alkoxides has been used to prepare inorganic ion exchange membranes. Metal alkoxides are easily hydrolyzed to form a metal hydroxide sol in the presence of acid. The sol is then repeatedly coated on a microporous inorganic membrane (alumina substrate) and heated to form a metal oxide on the substrate, which is an inorganic ion exchanger.139 Though this is also a heterogeneous membrane, some reported membranes show lithium ion permselectivity in electrodialysis.140... 

Crown ether carboxylic acids and alkyl esters are novel reagents port of alkali metal cations membranes. Metal Ion transport transport of protons. The in variation within the ionizabl molecule upon the selectivity petitive alkali metal transport liquid surfactant (emulsion) liquid membranes is assessed. 

This chapter focuses on the analytical aspects of solvent extraction on microchips. Although there are several reports in the literature on the application of chemical reactions, the topics dealt with here are limited only to application using parallel (side-by-side) flow schemes inside microchannels. Other examples, such as using a porous membrane, metal mesh, or droplets lie outside the scope of this chapter. 

---