Bio selective membrane

G. A. Rechnitz, Bio-Selective Membrane Electrodes in Trace Organic Analysis,... 

Rechnitz, G.A. Kobos, R.K. Riechel, S.J. Gebauer, C.R. A bio-selective membrane electrode prepared with living bacterial cells. Anal. Chim. Acta 1977, 94, 357-365. 

Rl. Rechnitz, C. A., Bio-selective membrane electrode probes. Science 214,287-291 (1987). 

Rechnitz GA, Arnold MA, Meyerhoff ME (1979) Bio-selective membrane electrode using... 

Ion-selective bulk membranes are the electro-active component of ion-selective electrodes. They differ from biological membranes in many aspects, the most marked being their thickness which is normally more then 105 times greater, therefore electroneutrality exists in the interior. A further difference is given by the fact that ion-selective membranes are homogeneous and symmetric with respect to their functioning. However, because of certain similarities with biomembranes (e.g., ion-selectivity order, etc.) the more easily to handle ion-selective membranes were studied extensively also by many physiologists and biochemists as model membranes. For this reason research in the field of bio-membranes, and developments in the field of ion-selective electrodes have been of mutual benefit. 

Graft copolymers combine the properties of their polymeric constituents and as such are polymer alloys, which open a vast field of new polymeric species. This is why active research along these lines is performed in many academic and industrial research laboratories all over the world. However, only few applications have reached a commercial level today. They involve the production of specific polymeric adhesives, perm-selective membranes, bio-medical devices and the surface modification of certain products. 

THE BIO MEDICAL AND RELATED ROLES OF ION-SELECTIVE MEMBRANE ELEC-... 

To conclude, bio-oU, the hquid product formed from fast pyrolysis of biomass, can be considered as one of the most promising renewable feedstocks for hydrogen or syngas production. Nevertheless, deactivation of catalysts often occurs during SR of biooil (Zhang et al., 2014), and the use of H2-selective membranes even increases this problem as the hydrogen is removed from the reaction side. 

This short review cannot be comprehensive as of the exponential increase of the literature dealing with new procedures and applications. Table 2 summarizes selected data and lists fields of application. For a more inclusive view on the subject the interested reader is referred to existing monographs6-161 or to the critical biennial review in Analytical Chemistry. As the readers of this general volume on membranes most likely are acquainted with electro-analytical sensors, this article will be limited to the introduction of a theoretical approach which might be helpful also to researchers in the bio-membrane field. 

Several techniques for VOC removal have been investigated such as thermal incineration, catalytic oxidation, condensation, absorption, bio-filtration, adsorption, and membrane separation. VOCs are present in many types of waste gases and are often removed by adsorption [1]. Activated carbon (AC) is commonly used as an adsorbent of gases and vapors because of its developed surface area and large pore volumes [2]. Modification techniques for AC have been used to increase surface adsorption and hence removal capacity, as well as to improve selectivity to organic compounds [3]. 

The fact that the species transferred across the sensor membrane (the analyte or reaction product) must be a gas limits application of this type of flowthrough sensor, which, however, is still more versatile than are the sensors based on integrated separation (gas diffusion) and detection [4] described in Section 4.2 in fact, while these latter can only exploit physico-chemical properties of the analytes transferred, sensors based on triple integration allow the implementation of a (bio)chemical reaction and formation of a reaction product, so they are applicable to a much wider variety of systems with adequate sensitivity and selectivity. 

Methods for (bio)catalyst retention include (i) heterogenization on supports (ii) recovery through phase change, such as precipitation or extraction of the catalyst and (iii) membrane filtration of a homogeneous catalyst. All methods, in principle, enable repeated use of a chiral catalyst without much loss of activity or selectivity. In a recent review (Kragl, 2001), examples are given from laboratory and... 

Additionally, membranes have the unique advantage of allowing the simultaneous contact with two different media, at each membrane side, creating compartments with different properties. Therefore, membranes offer the potential to promote the spatial organization of catalytic compartments and selective barriers. This feature is used with advantage in new concepts of membrane multiphasic (bio)reactors and membrane contactors. 

The selection ofthe membrane to be used in enzymatic membrane reactors should take into account the size of the (bio)catalyst, substrates, and products as well as the chemical species ofthe species in solution and ofthe membrane itself. An important parameter to be used in this selection is the solute-rejection coefficient, which should... 

Sodium ion-selective field-effect transistors (Na+ ISFETs) were prepared by using three different types of polymeric matrix materials, such as polyvinyl chloride, bio-compatible polymer (polyurethane) and Urushi (natural oriental lacquer). Their electrochemical characteristics were discussed in connection with their characteristics of polymeric matrix membranes. 

The biomimetic membranes represent a special group of carrier membranes. They are artificial membranes based on biomembrane mimicking, i.e., imitation of the essential features bio membranes use for separation. Nitrocellulose filters impregnated with fatty acids, their esters, and other lipid-like substances may be used— in other words, an imitation of many nonspecific barrier properties of biomembranes. The transport of gas through these membranes will essentially be according to facilitated transport (see Section 4.2). Biomimetic membranes for CO2 capture will transport the gas as HCO3. Development of these materials may be expected for selected applications. 

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