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[en] Regularities of boron compounds concentration during electrodialysis freshening of model solution of thermal water of Pauzhet geothermal power plant were investigated. It is shown that brines containing 4.7 g/l of boric acid are formed in condition of using membranes MF-4-SK and MA-40 and decreasing total salt content (pH > 10) up to 300 mg/dm3. 6 refs., 1 fig., 1 tab
[en] The great advances in nanotechnology call for advances in miniaturized power sources for micro/nano-scale systems. Nanofluidic channels have received great attention as promising high-power-density substitutes for ion exchange membranes for use in energy harvesting from ambient ionic concentration gradient, namely reverse electrodialysis. This paper proposes the nanofluidic crystal (NFC), of packed nanoparticles in micro-meter-sized confined space, as a facile, high-efficiency and high-power-density scaling-up scheme for energy harvesting by nanofluidic reverse electrodialysis (NRED). Obtained from the self-assembly of nanoparticles in a micropore, the NFC forms an ion-selective network with enormous nanochannels due to electrical double-layer overlap in the nanoparticle interstices. As a proof-of-concept demonstration, a maximum efficiency of 42.3 ± 1.84%, a maximum power density of 2.82 ± 0.22 W m−2, and a maximum output power of 1.17 ± 0.09 nW/unit (nearly three orders of magnitude of amplification compared to other NREDs) were achieved in our prototype cell, which was prepared within 30 min. The current NFC-based prototype cell can be parallelized and cascaded to achieve the desired output power and open circuit voltage. This NFC-based scaling-up scheme for energy harvesting based on NRED is promising for the building of self-powered micro/nano-scale systems. (paper)
[en] This paper presents a novel microplatform for high power generation based on reverse electrodialysis. The ideal cation-selective membrane for power generation was realized using geometrically controlled in situ self-assembled nanoparticles. Our proposed membranes can be constructed through a simple and cost-effective process that uses microdroplet control with nanoparticles in a microchannel. Another advantage of our system is that the maximum power and energy conversion efficiency can be improved by changing the geometry of the microchannel and proper selection of the nanoparticle size and material. This proposed platform can be used to supply power sources to other microdevices and contribute to a fundamental understanding of ion transport behavior and the power generation mechanism
[en] The membrane tangential filtration technologies are separation techniques based on the use of semipermeable filters through which, under a pushing force, it is possible to obtain the separation of components suspended or in solution according to their dimensional characteristics and / or chemical-physical . The membrane technologies are clean separation techniques and energy-efficient, especially suitable for applications in the agro-food sector. At the laboratories of the ENEA Research Center Casaccia, they have been researched and developed various membrane filtration processes in the agri-food sector.
[it]Le tecnologie di filtrazione tangenziale a membrana sono tecniche separative basate sull'impiego di filtri semipermeabili attraverso i quali, sotto una forza spingente, e' possibile ottenere la separazione di componenti sospese o in soluzione in funzione delle loro caratteristiche dimensionali e/o chimico-fisiche. Le tecnologie di membrana sono tecniche separative pulite e a basso consumo energetico, particolarmente indicate per applicazioni nel settore agro-alimentare. Presso i laboratori del Centro Ricerche ENEA della Casaccia, sono stati studiati e messi a punto diversi processi di filtrazione a membrana nel settore agro-alimentare.
[en] Presently, the most important application of ion exchange membranes (IEM) is the electrodialysis. This technique consists of a membrane separation using a series of anion exchange membranes alternately and cations, often used for the desalination of brackish water. These membranes are confronted with problems of aging. Indeed, the more they are used more physical and chemical properties will change. A comparative study of the behavior of both EMI and new but the same treatment is carried out by measuring a magnitude transfer characteristic: ion permeability. Ionic permeability is a physical quantity can have an idea about the selectivity of the membrane towards the charged species and the porosityof the membrane. It is a transport of ions (cations + anions) through the membrane. Thus, determining the ion permeability is to determine the diffusion flux of a strong electrolyte through a membrane separating two compartments (one containing electrolytes and other water initially ultrapure who will gradually electrolyte through the membrane). The measurement technique used is that by conductimetric detection because of the ease of its implementation and its accuracy. Thus, the variation of the concentration of the electrolyte is continuously monitored by measuring the conductivity of the solution diluted with time. The curves s = f (t) MEA and MEC new and used varying concentration of the electrolyte membranes show that let in less waste of strong electrolyte (NaCl and HCl) than new ones. This can be explained by: - The functional sites are combined with polyvalent ions present even in trace amounts in the solution process and become inactive. The membrane loses its hydrophilic character and turns into a film almost hydrophobic. - The chemical attacks and electrodialysis operations have degraded and eliminated much of the fixed sites leading to the same effects on the hydrophilic membrane. - These two assumptions have been reinforced by the extent of exchange capacities of these new membranes and worn. Indeed, there is a marked decrease of this magnitude in the case of membrane treatment. - Extensive use of these membranes in the presence of media loaded molecules organic causes plugging gaps left open by the chains macromolecular. Such gaps are space travel and dissemination of electrolytes. The comparative study of ionic permeability of new and used IEM showed that over the membrane permeability is worn over the electrolyte is low. This was attributed to inhibition of some functional sites, and the clogging of interstices by organic molecules. FTIR tests are underway to confirm the presence of these macromolecules in the membrane treatment.
[en] This study was carried out with solutions of 5000, 3000 and 1000 ppm of NaCl, and 3000 and 1000 ppm of NaSO4. A stack-pack of 20 pairs membranes, Nepton lonics 61 AZL 183 -cationic- and 111 BZL 183 -anionic- with 220 cm2/membrane was used. For the above mentioned Solutions the following values were determined: Limiting current density; the values of n and K in the expression which relates the L.C.D. with flow rate; dependence of spent energy on flow rate; spent energy and time of operation versus initial current and concentration of the solution, and finally the influence of the concentration potential on the electrodialytic process. A discussion of the results obtained is included. (Author) 18 refs
[en] In the research the main desalination processes of sea and brackish water are analyzed and discussed. The processes can be separated into the categories of Thermal and Membrane Processes. The thermal processes can be further divided between those in which heat is supplied to the water, causing its evaporation (single-step evaporation processes, Multi flash processes and multiple effects processes of evaporation), and those, less frequently used, where the heat is instead subtracted, causing a phenomenon of crystallization. The membrane processes, on the other side, are based on the passage of salt or brackish water through synthetic semi-permeable membranes. They can be subdivided between those employing reverse osmosis processes, where the selective solvent passage through the membranes is guaranteed by high pressure differences and those based on electrodialysis.
[it]Nella ricerca vengono analizzati e discussi i principali processi di dissalazione delle acque marine e salmastre, che possono essere distinti nelle due categorie di Processi Termici e Processi a Membrana. I processi termici vengono quindi distinti tra quelli in cui viene fornito calore all'acqua, determinandone l'evaporazione (processi di evaporazione monostadio, processi multiflash e processi di evaporazione ad effetti multipli), e quelli, molto meno utilizzati, in cui il calore e invece sottratto, determinando un fenomeno di cristallizzazione. I processi a membrana, invece, prevedono il passaggio dell'acqua salata o salmastra attraverso membrane sintetiche semi-permeabili. La principale distinzione operabile tra i processi a membrana riguarda i processi ad osmosi inversa, in cui si impongono elevate differenze di pressione per consentire il passaggio attraverso le membrane del solo solvente (inibendo il passaggio degli ioni), e quelli ad elettrodialisi.
[en] Surface modification of polyvinylchloride based heterogeneous cation exchange membrane was performed by graft polymerization of PAA and PAA-co-PANI/MWCNTs nanoparticles. The ion exchange membranes were prepared by solution casting technique. Spectra analysis confirmed graft polymerization clearly. SEM images illustrated that graft polymerization covers the membranes by simple gel network entanglement. The membrane water content was decreased by graft polymerization of PAA-co-PANI/MWCNTs nanoparticles on membrane surface. Membrane transport number and selectivity declined initially by PAA graft polymerization and then began to increase by utilizing of composite nanoparticles in modifier solution. The sodium and barium flux was improved sharply by PAA and PAAco- 0.01%wt PANI/MWCNTs graft polymerization on membrane surface and then decreased again by more increase of PANI/MWCNTs nanoparticles content ratio in modifier solution. The electrodialysis experiment results in laboratory scale showed higher dialytic rate in heavy metals removal for grafted-PAA and grafted-PAA-co-PANI/MWCNTs modified membrane compared to pristine one. Membrane areal electrical resistance was also decreased by introducing graft polymerization of PAA and PAA-co-PANI/MWCNTs NPs on membrane surface.