Potential of membrane

Comparison of the calculated and observed changes in the EMF is shown in Table 1. It can be seen that the calculated changes in the phase boundary potential of membranes with 1.0 mM 1-3 in contact with 0.1 and 0.01 M aqueous KCl or RbCl were in good agreement with the corresponding observed values. Such an agreement indicates that it is reasonable to apply the present surface model to explain that the phase boundary potential is, in fact, determined by the amount of the primary cation permeated into or released out of the membrane side of the interface. 

L. Wojtczak and M. J. Natecz, The surface potential of membranes Its effect on membrane-bound enzymes and transport processes, in Structure and Properties of Cell Membranes (G. Benga, ed.), Vol. II, pp. 215-242, CRC Press, Boca Raton, Florida (1985). 

Spector, A. A., and Burns, C. P., 1987, Biological and therapeutic potential of membrane lipid modification in tumors, Cancer Res. 47 4529-4537. 

J. Woltinger, H.-P. Krimmer and K. Drauz, The potential of membrane reactors in the asymmetric opening of meso-anhydrides, Tetrahedr. Lett. 2002,43, 8531-8533. 

The following example illustrates the potential of membrane-separation processes for precombustion carbon capture in an IGCC. This approach avoids using an expensive air-separation unit (asu) or a difficult-to-implement high-temperature mixed-ion conducting membrane process however, it still enables capture of C02 at purities suitable for commercial use or sequestration. 

As previously reported, membrane contactors present interesting advantages with respect to traditional units. Moreover, they well respond to the main targets of the process intensification, such as to develop systems of production with lower equipment-size/production-capacity ratio, lower energy consumption, lower waste production, higher efficiency. In order to better identify the potentialities of membrane contactors in this logic, they have been recently compared to traditional devices for the sparkling-water production in terms of new defined indexes [24]. In particular, the comparison has been made at parity of plant capacity and quality of final product. The metrics used for the comparison between membranes and traditional units are ... 

Note that, in particular, aspect (1) is relevant for the evaluation of the potential of membrane reactors aiming to withdraw products via permeable walls. 

The Gruen—Marcelja model could relate the hydration force to the physical properties of the surfaces by assuming that the polarization of water near the interface is proportional to the surface dipole density.9 This assumption led to the conclusion that the hydration force is proportional to the square of the surface dipolar potential of membranes (in agreement with the Schiby—Ruckenstein model),6 a result that was confirmed by experiment.10 However, subsequent molecular dynamics simulations revealed that the polarization of water oscillated in the vicinity of an interface, instead of being monotonic.11 Because the Gruen—Marcelja model was particularly built to explain the exponential decay of the polarization, it was clearly invalidated by the latter simulations. Other conceptual difficulties of this model have been also reported.12 13... 

It is interesting to note that i/ oi and 1//02, are, respectively, the unperturbed surface potentials of membranes 1 and 2 (i.e., the surface potentials at /i = 00) and that Eq. (16.9) states that the interaction force is proportional to the product of the unperturbed surface potentials of the interacting membranes. This is generally true for the Donnan potential-regulated interaction between two ion-penetrable membranes in which the distribution of the membrane-fixed charges far inside the membranes is uniform but may be arbitrary in the region near the membrane surfaces (see Eq. (8.28)). 

After it was recognized that pH glass electrodes were not permeable to hydrogen ions, the systematic development of new electrodes became more intellectually feasible. We have probably only begun to explore the potentialities of membrane electrodes. These electrodes should be thought of as ion-selective rather than ion-spedfic, since... 

This statement summarizes the discussions at a conference on the Exploration of the potential of membrane technology for sustainable decentralized sanitation held in Italy (at Villa Serbelloni, Bellagio) on 23-26 April 2003 [1]. ... 

The interesting results obtained, not only with PEEK-WC but also with other materials, encourage further research work to better understand and improve the potentialities of membranes in biomedical applications. 

The applications mentioned demonstrate the potential of membrane reactors for the recovery and repeated use of homogeneously soluble catalysts. For some of the examples a strong increase in the total turnover number has been achieved. First publications indicate that this technique is also being investigated by industry [58]. Due to the additional steps required for coupling as well as for the equipment necessary it might be applicable in the majority to high value-added products. On... 

The potential of membrane separation techniques (such as cross-flow microfiltration(MF), ultrafiltration (UF), Reverse Osmosis (RO)and electrodialysis (ED) ) and membrane reactors in the treatment of fermentation broths are huge. The synergistic effects obtainable by designing the overall biotechnological process combining various membrane technique are particularly significant. 

At various places throughout the first five chapters in the book we have, when it appeared relevant to the discussion, referenced studies which addressed issues pertaining to the economic/technical feasibility of membrane reactor processes. In this chapter we specifically focus our attention on these issues. In the discussion in this chapter we have, by necessity, drawn our information from published studies and reports. Several proprietary studies reportedly exist, carried out by a number of industrial companies, particularly during the last decade, which have evaluated the potential of membrane reactors for application in large-scale catalytic processes. By all accounts the conclusions reached in these proprietary reports mirror those found in the published literature. In the discussion which follows, we will first discuss catalytic and electrochemical reactors. We will then conclude with a discussion on membrane bioreactors. 

The real potential of membrane reactors becomes evident with coenzyme dependent enzymatic systems.10 20 21 Coenzymes, like NAD+ or NADP+, usually have a long term effect on enzyme activity only if they can move from one enzyme, able to oxidize them, to another, able to reduce them, in loop kinetics. Continuous homogenous catalysis is then a prerequisite to achieving high reaction yields. Enzyme membrane reactors offer a suitable reaction environment provided that coenzymes are retained in the reaction system. Such compounds are in fact quite expensive, which limits the use of coenzyme dependent enzymes. Reverse osmosis (RO) membranes could be helpful in retaining native... 

The potential of membrane reactors has been widely verified and documented for a large number of reactions. However, all the studies made are stUl confined to the laboratory scale, and their implementation in industrial systems has yet to occur. Research into new membrane materials and improvement in the properties of currently available membranes (permselectivity, resistance to poisoning, stability, reduction of palladium thickness, etc.) are always in progress. The development of procedures to deposit the catalyst within the membrane structure without changing its initial permeability and selectivity is an example of the ongoing research for the preparation of catalytic membranes. 

This chapter presents an overview of different membrane processes and a description of all of the chapters presented in this edition. Chapter 2 focuses on updated information of utility to UF and NF membrane research and development, particularly in the preparation of new types of UF/NF membranes with improved performances. Chapter 3 presents a comprehensive review on RO membrane, the latest developments in the field, important installations demonstrating this technology, and future scope of RO processes. Chapter 4 presents the potential of membrane contactors, especially hollow fiber contactors in the field of chemical and nuclear industry along with their applications, performance, and current challenges faced by indnstry. This chapter also gives an introduction to membrane contactors, their principles of operation and associated mechanisms (where chemical reactions are involved), and fntnre scope of these contactors. 

P. Bernardo, G. Clarizia, Potential of membrane operations in redesigning industrial processes. The ethylene oxide manufacture, Chemical Engineering Transactions 25 (2011) 617-622. 

S. A1 Obaidani, E. Curcio, F. Macedonio, G. Di Profio, H. Al-Hinai, and E. Drioli, Potential of membrane distillation in seawater desalination Thermal efficiency, sensitivity study and cost estimation, J. Membr. Set 323 (2008) 85-98. 

Rode, S., Nguyen, R.T., Roizard, D., Bounaceur, R., Castel, C., Favre, E. 2012. Evaluating the intensification potential of membrane contactors for gas absorption in a chemical solvent A generic one-dimensional methodology and its application to CO2 absorption in monoethanolamine. J. Membr. Sci. 389 1-16. 

First applications of membrane reactors can be foimd in the field of bioprocess engineering using whole cells in fermentations or enzymatic bioconversions [6, 7]. Most of these processes use polymeric membranes, as temperatures seldomly exceed 60 °C. The development of inorganic membrane materials (zeolites, ceramics and metals) has broadened the application potential of membrane reactors towards the (petro) chemical industry [8]. Many of these materials can be applied at elevated temperatures (up to 1000°C), allowing their application in catalytic processes. 

Many efforts devoted to the development of membrane competitive applications by the most prestigious research centers worldwide attest the strategic importance and the potentiality of membrane reactors for the industry. The scientific production dealing with selective membrane reactors is growing exponentially as reported in Chap. 2, 750 papers on membrane reactors have been published in 2009, of which 220 on Pd-based membranes. The main processes in which R D departments are focusing the attention are those devoted to hydrogen production, for which two configurations are imder study ... 

However, laboratory scale reactor performance and assessments by mathematical models simulations have shown the real and excellent potentiality of membrane integration in chemical processes, leading to a strong increase of reactant conversion at lower operating temperatures. Table 11.1 summarizes the main outcomes reported in Chaps. 5, 6, 7, 8, and 9), where some interesting case studies have been presented and described. 

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