Artículos de revistas: "Counter-ion exchange"

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Murayama, Y. y M. Sano. "Collapsing Transition of DNA and Counter Ion Exchange". Seibutsu Butsuri 43, supplement (2003): S28. http://dx.doi.org/10.2142/biophys.43.s28_4.

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Coryn, G., A. Speecke y J. Hoste. "An Electronic Drop Counter for Ion Exchange Chromatography". Bulletin des Sociétés Chimiques Belges 66, n.º 1 (1 de septiembre de 2010): 650–53. http://dx.doi.org/10.1002/bscb.19570660154.

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3

Luo, Tao, Florian Roghmans y Matthias Wessling. "Ion mobility and partition determine the counter-ion selectivity of ion exchange membranes". Journal of Membrane Science 597 (marzo de 2020): 117645. http://dx.doi.org/10.1016/j.memsci.2019.117645.

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4

Srikanth, M. V., S. A. Sunil, N. S. Rao, M. U. Uhumwangho y K. V. Ramana Murthy. "Ion-Exchange Resins as Controlled Drug Delivery Carriers". Journal of Scientific Research 2, n.º 3 (24 de agosto de 2010): 597. http://dx.doi.org/10.3329/jsr.v2i3.4991.

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Ion exchange resins (IER) are insoluble polymers that contain acidic or basic functional groups and have the ability to exchange counter-ions within aqueous solutions surrounding them. Based on the nature of the exchangeable ion of the resin as a cation or anion, it is classified as cationic or anionic exchange resins, respectively. The efficacy of ion exchange resins mainly depends upon their physical properties such as degree of cross-linking, porosity, acid base strength, stability, purity and particle size. Modified release of drugs from resinate (drug-resin complexes) is another potential application of ion exchange resins. Due to the versatile utility of ion exchange resins, they are being used for various drug delivery and therapeutic applications. Resins used are polymers that contain appropriately substituted acidic groups, such as carboxylic and sulfonic for cation exchangers; or basic groups, such as quaternary ammonium group for anion exchangers. This review addresses different types of ion exchange resin, their properties, the chemistry; role of IER in controlled drug delivery systems, its therapeutic applications, methods of preparation of IER along with their resonates. Keywords: Anion exchange; Cation exchange; Resin; Controlled release; Resinates; Drug delivery. © 2010 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved. DOI: 10.3329/jsr.v2i3.4991 J. Sci. Res. 2 (3), 599-613 (2010)

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5

Zerdoumi, Ridha, Kafia Oulmi y Salah Benslimane. "Enhancement of counter-ion transport through ion-exchange membranes in electrodialytic processes". Desalination and Water Treatment 56, n.º 10 (17 de octubre de 2014): 2631–36. http://dx.doi.org/10.1080/19443994.2014.972734.

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6

Rubinstein, Isaak. "Theory of concentration polarization effects in electrodialysis on counter-ion selectivity of ion-exchange membranes with differing counter-ion distribution coefficients". Journal of the Chemical Society, Faraday Transactions 86, n.º 10 (1990): 1857. http://dx.doi.org/10.1039/ft9908601857.

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7

Kimizuka, Hideo, Hirohiko Waki, Akira Matsubara y Y\={o}ichi Arimoto. "Additivity Law for the Activity of a Counter Ion in Ion-Exchange Resin". Bulletin of the Chemical Society of Japan 60, n.º 5 (mayo de 1987): 1613–15. http://dx.doi.org/10.1246/bcsj.60.1613.

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8

Gan, L. "Micellar Effects on the Formation of the 1,3,5-Trinitrobenzene-Cyanide Complex in Water". Australian Journal of Chemistry 38, n.º 8 (1985): 1141. http://dx.doi.org/10.1071/ch9851141.

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The anionic σ-complex from cyanide ion and 1,3,5-trinitrobenzene in water was stabilized by cationic micelles. The binding of counter ions to the micellar head groups in hexadecyl-trimethylammonium cyanidefollowed a distribution model with the counter ion binding constant KCN = 1400 mol-1 dm3. The bromide-cyanide ion exchange constant, KCNBr, was equal to 1.28. These results rendered further support to the general applicability of the distribution model.

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9

Prajapati, M. N., P. M. Gaur y B. D. Dasare. "Brackish water desalination by a continuous counter-current ion-exchange technique". Desalination 52, n.º 3 (enero de 1985): 317–26. http://dx.doi.org/10.1016/0011-9164(85)80041-2.

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Nikolaev, N. P., V. A. Ivanov, V. I. Gorshkov, V. A. Nikashina y N. B. Ferapontov. "Counter-current ion-exchange separation of strontium from brines with acrylic-type cation-exchange resins". Reactive Polymers 18, n.º 1 (agosto de 1992): 25–33. http://dx.doi.org/10.1016/0923-1137(92)90291-9.

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Gorshkov, V. I., A. I. Novoselov, N. B. Ferapontov, O. T. Gavlina, B. F. Fedushkin y O. I. Agatova. "Wasteless process of ion exchange preparation of KNO3 using counter-current columns". Reactive Polymers 17, n.º 1 (abril de 1992): 120. http://dx.doi.org/10.1016/0923-1137(92)90590-x.

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12

Tang, Ying, Beibei Tang y Peiyi Wu. "Preparation of a positively charged nanofiltration membrane based on hydrophilic–hydrophobic transformation of a poly(ionic liquid)". Journal of Materials Chemistry A 3, n.º 23 (2015): 12367–76. http://dx.doi.org/10.1039/c5ta01823d.

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A positively charged NF composite membrane with high permeability was obtained via a simple counter-ion exchange reaction in an aqueous solution, due to the hydrophilic–hydrophobic transformation of the PIL.

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13

Ozvald, Adam A., Monika R. Klezcek, Antonio C. Rodrigo y J. Scott Parent. "ISOBUTYLENE-RICH IMIDAZOLIUM IONOMERS: INFLUENCE OF ION-PAIR DISTRIBUTION AND COUNTER-ANION STRUCTURE". Rubber Chemistry and Technology 91, n.º 2 (1 de abril de 2018): 303–19. http://dx.doi.org/10.5254/rct.18.83700.

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ABSTRACT New chemistry for overcoming the limitations of nonpolar elastomers is detailed, with particular emphasis on improving interfacial adhesion and the intensity of polymer–filler interactions. The chemical modification of brominated poly(isobutylene-co-isoprene) and brominated poly(isobutylene-co-para-methyl styrene) is used to introduce small amounts of imidazolium bromide functionality. Unlike conventional isobutylene-rich elastomers, ionomer derivatives bearing vinylimidazolium bromide groups are peroxide curable. The ultimate cross-link density, along with accompanying thermoset properties, can be tailored by changing the amount and distribution of N-vinylimidazolium and N-butylimidazolium functionality. Moreover, the counteranion can be exchanged from bromide to sulfonate or vinylsulfonate to further optimize adhesive, tensile, and stress relaxation properties. Bromide exchange anionic montmorillonite clay platelets can yield thermoset ionomer nanocomposites with a high degree of reinforcement despite a relatively low filler loading.

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14

Leguay, Sébastien, Peter G. C. Campbell y Claude Fortin. "Determination of the free-ion concentration of rare earth elements by an ion-exchange technique: implementation, evaluation and limits". Environmental Chemistry 13, n.º 3 (2016): 478. http://dx.doi.org/10.1071/en15136.

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Environmental context The lanthanides are a group of heavy elements (from lanthanum to lutetium) increasingly used in many electronic consumer products and little is known about their environmental mobility and toxicity. In natural systems, these elements will bind to natural organic matter but metal toxicity is usually defined by the free metal ion concentration. Here, we propose a method based on sample equilibration with an ion-exchange resin to measure the free lanthanide ion concentration in the presence of natural organic matter. Abstract An ion-exchange technique that employs a polystyrene sulphonate ion-exchange resin was developed for determining environmentally relevant free-ion concentrations of Ce, Eu, La and Nd. Owing to the high affinity of rare earth elements (REE) for the selected resin, this method requires the addition of an inert salt to increase the concentration of the counter-ions (i.e. cations that are exchanged with REE bound to the resin). The use of a batch equilibration approach to calibrate the resin allowed the implementation of the ion-exchange technique at reasonably low ionic strength (I = 0.1M). Several ligands were used to test the selectivity of the method, which proved to be highly selective for the free metal ion in presence of the tested cationic and anionic complexes (REE–nitrate, REE–malic acid and REE–nitrilotriacetic acid systems) and operational for very low proportions of REE3+, owing to the strong REE–resin interactions. The ion-exchange technique was also implemented to determine [Eu]inorg in the presence of natural humic matter (Suwannee River Humic Acid) and the results were compared with those obtained using equilibrium dialysis and those calculated with chemical equilibrium models. At pH 4.00, the measured [Eu]inorg values were in fairly good agreement with those predicted with the Windermere Humic Aqueous Model and Stockholm Humic Model, whereas the Non-Ideal Competitive Absorption model appeared to underestimate the [Eu]inorg. However, the inorganic europium concentrations were strongly underestimated (4 < [Eu]inorg, IET/[Eu]inorg, calc < 18) with the three prediction models at higher pH (5.3 and 6.2).

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Mejia-Ariza, Raquel y Jurriaan Huskens. "The effect of PEG length on the size and guest uptake of PEG-capped MIL-88A particles". Journal of Materials Chemistry B 4, n.º 6 (2016): 1108–15. http://dx.doi.org/10.1039/c5tb01949d.

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Different PEG length capping ligands were used to fabricated micro- and nano-MIL-88A particles. A model drug was encapsulated and released by counter-ion exchange, and its rate was dependent on the presence of PEG chains on the surface.

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Dolgonosov, Anatoly M., Ruslan Kh Khamizov y Nadezhda K. Kolotilina. "Nano-ion-exchangers - a new class of reactive materials". Сорбционные и хроматографические процессы 18, n.º 6 (6 de diciembre de 2018): 794–809. http://dx.doi.org/10.17308/sorpchrom.2018.18/607.

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Nano-sized particles of functional polymers i.e. nano-ion-exchangers (NIEX), are unusual objects which simultaneously behave as the hyper-charged ions and the solid ion exchangers. Due to similar charges, they form very stable colloidal systems. This paper is devoted to theoretical and practical study of the proper- ties of nano-exchangers, methods for their preparation, the technique of experiments being practically un- known, and the opportunities for their application. The results of dynamic experiments are given for sorption of nano-exchangers and the ions of back- ground solutions on the beds of macro-particles of usual cationic and anionic resins. It is shown how to ob- tain the NIEX hydrosols with the desired ionic composition, and the concept of the standard state hydrosol is defined. The possibility for solid-phase exchange of counter ions between contacting particles of the same polarity is demonstrated. The possibilities and advantages of using nano-ion-exchangers in chemical analysis are demonstrat- ed by different examples: preparation of separating phases for ion chromatography, application as modifier in capillary electrophoresis and using in photo-luminescence. The prospects of nano-ion-exchangers for drug delivery are also shown.

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17

Oulmi, K., K. E. Bouhidel y G. M. Andreadis. "Noise spectra of K+ and NH4+ ions at over-limiting current in an electrochemical system with a cation exchange membrane". Journal of Water Reuse and Desalination 3, n.º 3 (12 de marzo de 2013): 291–96. http://dx.doi.org/10.2166/wrd.2013.001.

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The present work investigates the effect of the counter ion nature on the noise of the over-limiting current (Iov). Moreover, the electrochemical methods, current voltage curve (I–V) and the chronopotentiometry (V–t) measurements are applied. The over-limiting current is always accompanied by a neat electrical noise. It is a well accepted experimental phenomenon. The study of this noise may contribute to a better understanding of the Iov and the feasibility of electrodialysis operation at this current in terms of energy consumption. The electrical noise depends directly on the counter ion nature. The power spectral density of the membrane's potential fluctuation was obtained via Fourier analysis of the time series recorded during the transport of counter ions (K+ and NH4+). The spectra are evaluated above the limiting current indicating the differences between the K+ and the NH4+. It is found that the cation NH4+ presents a singular behaviour and the noise is minimal.

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18

Nwal Amang, D., S. Alexandrova y P. Schaetzel. "The determination of diffusion coefficients of counter ion in an ion exchange membrane using electrical conductivity measurement". Electrochimica Acta 48, n.º 18 (agosto de 2003): 2563–69. http://dx.doi.org/10.1016/s0013-4686(03)00298-6.

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19

Kamcev, Jovan, Michele Galizia, Francesco M. Benedetti, Eui-Soung Jang, Donald R. Paul, Benny D. Freeman y Gerald S. Manning. "Partitioning of mobile ions between ion exchange polymers and aqueous salt solutions: importance of counter-ion condensation". Physical Chemistry Chemical Physics 18, n.º 8 (2016): 6021–31. http://dx.doi.org/10.1039/c5cp06747b.

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Equilibrium partitioning of ions between a membrane and a contiguous external solution strongly influences transport properties of polymeric membranes used for water purification and energy generation applications.

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20

Mir, Fasil Qayoom y Anupam Shukla. "Sharp decline in counter-ion transport number of electrodialysis ion exchange membrane on moderate increase in temperature". Desalination 372 (septiembre de 2015): 1–6. http://dx.doi.org/10.1016/j.desal.2015.06.009.

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21

Tian, Zizun, Zhonglu Qi, Yuhao Yang, Hailong Yan, Qianqiao Chen y Qin Zhong. "Anchoring CuS nanoparticles on accordion-like Ti3C2 as high electrocatalytic activity counter electrodes for QDSSCs". Inorganic Chemistry Frontiers 7, n.º 19 (2020): 3727–34. http://dx.doi.org/10.1039/d0qi00618a.

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A Ti₃C₂/CuS composite has been fabricated as a counter electrode for quantum dot-sensitized solar cells by anchoring CuS nanoparticles on Ti₃C₂via a facile ion-exchange method at room temperature.

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Dzyazko, Yuliya, Vladimir Zakharov, Yevhen Kolomiiets y Kateryna Kudelko. "COMPOSITE ION-EXCHANGES FOR THE RECYCLING OF LIQUID WASTE OF DAIRY INDUSTRY". Ukrainian Chemistry Journal 86, n.º 5 (15 de julio de 2020): 38–52. http://dx.doi.org/10.33609/2708-129x.86.5.2020.38-52.

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The method of directed formation of particles of hydrated zirconium and titanium oxides into anion exchange resins has been developed. The approach based on the Ostwald-Freundlich thermodynamic equation is applied. Such approach, in particular, connects the size of particles with the solubility of the compound, volume and concentration of reagents. Less soluble zirconium dioxide is deposited as non-aggregated nanoparticles, the size of which does not exceed 10 nm. The composition of such composites is the most reproducible. In the case of more soluble titanium dioxide, aggregates of nanoparticles (up to 70 nm) are formed. When the concentration of the solution of metal salts in the polymer increases, the particles of micron size are deposited, the composition of this type of material is less reproduced. Non-aggregated nanoparticles increase the exchange capacity of the polymer. This leads to an increase in its electrical conductivity in 1.4-1.8 times. This is due to an increase in the concentration of mobile charge carriers in the polymer matrix that is caused by reducing its swelling. Other reason is a contribution of the counter-ions of the functional groups of inorganic component to ion transport. On the contrary, the aggregates of nanoparticles amplify the polymer swelling, resulting in a reduction of exchange capacity and electrical conductivity. Ion-exchangers were used for the ion exchange processing of nanofiltration permeate of milky whey, and for electromembrane desalination of protein concentrate.

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23

Matos, C. T., S. Velizarov, J. G. Crespo y M. A. M. Reis. "Removal of bromate, perchlorate and nitrate from drinking water in an ion exchange membrane bioreactor". Water Supply 5, n.º 5 (1 de diciembre de 2005): 9–14. http://dx.doi.org/10.2166/ws.2005.0033.

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The presence of anionic micropollutants, such as bromate, perchlorate and nitrate, in drinking water supplies represents a risk for public health. This work evaluates the applicability of the ion exchange membrane bioreactor (IEMB) concept for their removal. The IEMB concept combines the transport of anionic pollutants, through a dense mono-anion permselective membrane, with their simultaneous biodegradation to harmless products by a suitable microbial culture in a separated biocompartment. The transport of the pollutant counter-ions (anions) is governed by the Donnan equilibrium principle and, therefore, it is possible to enhance it by using a more concentrated driving counter-ion (e.g. chloride) added to the biocompartment. The IEMB process proved to selectively remove nitrate and perchlorate to concentrations below the recommended levels of 4 ppb for ClO4− and 25 ppm of NO3−, from a model polluted stream containing 100 ppb of ClO4− and 60 ppm of NO3−. Transport studies, made under Donnan dialysis conditions, showed bromate fluxes comparable to those obtained for nitrate under similar experimental conditions. However, the rate of biological reduction of bromate was about one order of magnitude slower than that of nitrate.

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Zerdoumi, Ridha, Hadjer Chatta, Dhaouadi Mellahi, Kafia Oulmi, Mahmoud Ferhat y Ali Ourari. "Chronopotentiometric evaluation of enhanced counter-ion transport through anion exchange membranes in electromembrane processes". DESALINATION AND WATER TREATMENT 78 (2017): 34–40. http://dx.doi.org/10.5004/dwt.2017.20871.

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Velizarov, S., J. G. Crespo y M. A. Reis. "Removal of nitrate from water in a novel ion exchange membrane bioreactor". Water Supply 2, n.º 2 (1 de abril de 2002): 161–67. http://dx.doi.org/10.2166/ws.2002.0059.

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Biological denitrification in a novel ion exchange membrane reactor (IEMB) has been investigated. The polluted water was separated from the mixed denitrifying culture by a non-porous, mono-anion permselective membrane providing continuous exchange of nitrate for chloride added as a counter-ion to the biocompartment. A removal efficiency of 87% and a surface removal rate of about 1,400 mg NO3- m-2h-1 was achieved at a nitrate concentration of 150 mg NO3- L-1. The treated water stream was essentially free of ethanol, used as a carbon source, and NO2- ions whereas the original water conductivity was completely preserved due to very efficient Donnan exclusion of the cations present in the two solutions from the membrane used. The IEMB process showed higher removal efficiency and better nitrate selectivity compared to a Donnan dialysis process operated under similar conditions.

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Asante-Sackey, Dennis, Sudesh Rathilal, V. L. Pillay y Emmanuel Kweinor Tetteh. "Effect of ion exchange dialysis process variables on aluminium permeation using response surface methodology". Environmental Engineering Research 25, n.º 5 (8 de octubre de 2019): 714–21. http://dx.doi.org/10.4491/eer.2019.297.

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This study investigated aluminum permeation using a counter flow ion exchange dialysis (IED) system. The optimum conditions for permeation were investigated using response surface methodology (RSM). Effect of four factors- feed concentration (100-2,000 ppm, A), feed flow rate (25-85%, B), sweep concentration (0.25-1 N HCl, C) and sweep flow rate (25-85%, D) were studied using face centered central composite (FC-CCD) statistical experimental design. A RSM model was developed based on the experimental permeation data and the response plot was developed. The FC-CCD model predicted permeation correlated with the experimental data. The regression coefficient (R<sup>2</sup>) was found to be 0.9568. The experiment showed the ascending order of the effect of the variables is D < B < C < A. In a counter flow IED for Al permeation, the sweep flow rate is insignificant (p > 0.05). Experimental validation demonstrated for target permeation of 70% was 68.8% ± 2.22%. This suggested that the RSM was a suitable tool in optimizing Al-permeation.

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Zhao, Yue, Lei Li, Ling-Yun Wang, Xiao-Peng Li, Xin-Bo Wang, Zuo-Hui Ji, He-Guo Li, Quan-Fu Men y Jin-Yi Zhong. "Preparation and Chemical Protective Clothing Application of Sulfonated Poly(2,6-dimethyl-1,4-phenyleneoxide)". Science of Advanced Materials 13, n.º 4 (1 de abril de 2021): 583–90. http://dx.doi.org/10.1166/sam.2021.3903.

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The preparation of chemical protective clothing (CPC) materials with excellent protective performance and physiological comfort have always been a global challenge. The selective permeability of organic matter and water shown by polyelectrolyte membranes in fuel cells and other applications provides ideas for solving this problem. This research focused on sulfonated poly(2,6-dimethyl-1,4-phenylene oxide) (SPPO), a polyelectrolyte membrane material with excellent performance, and carried out different counter-ion substitutions to prepare a series of membrane materials, and their mechanical properties, contact angle, permeability, and selectivity. The performance was tested and compared with Nafion, a typical commercial membrane. The results show that the SPPO membrane has the potential of CPC application and the performance of the membranes can be controlled by the simple method of adjusting the counter-ion exchange of the membrane material.

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Schippers, D., M. Kooi, P. Sjoerdsma y F. de Bruijn. "Colour removal by ion exchange and reuse of regenerant by means of nanofiltration". Water Supply 4, n.º 5-6 (1 de diciembre de 2004): 57–64. http://dx.doi.org/10.2166/ws.2004.0093.

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In the past year Vitens, The Netherlands' largest water supply company, and Witteveen+Bos, have prepared the preliminary, basic and detailed design for a full-scale ion exchange plant reducing colour in drinking water to a value of less than 10 mg/l PtCo. Current pilot study shows that the results are even better than expected. The plant will be built in 2004 and start-up is scheduled for mid 2005. The introduction of ion exchange at WTP (Water Treatment Plant) Oldeholtpade is part of a larger project, also including softening in pellet reactors, preceded by counter-current aeration and renovation of the existing treatment plant. The colour content present in groundwater is caused by peat layers. In contrast with conventional ion exchange processes, previous pilot studies showed that the exchange capacity of the resin for organics is much larger than expected. The excellent results can be explained by assuming the simultaneous occurrence of adsorption and ion exchange processes on the resin. It can be concluded that optimising operating conditions, such as higher exchange capacity (as KMnO4/liter resin), higher superficial velocity, shorter contact time and longer filter run cycle clearly affect resin volume as well as the required amount of regenerant. Vitens has started additional experiments at WTP Spannenburg to confirm the innovative design parameters. Aim of the research is the relation between adsorption and ion exchange during filtration, in order to clarify the achieved results. Furthermore the relationship between the specific water type (characterisation of organic compounds) and the operational results of ion exchange will be studied. In order to minimise the waste regenerant, treatment towards recycling is studied by dead end nanofiltration. With nanofiltration it is possible to concentrate the waste stream to a maximum of 10% of the original waste stream. The recovered regenerant can be recycled for regeneration of the resin.

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Quast, K. B. "Counter-current ion exchange for the removal of organically bound sodium from low-rank coals". Minerals Engineering 13, n.º 13 (noviembre de 2000): 1423–28. http://dx.doi.org/10.1016/s0892-6875(00)00124-2.

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Che, Canyan, Mikhail Vagin, Ujwala Ail, Viktor Gueskine, Jaywant Phopase, Robert Brooke, Roger Gabrielsson et al. "Twinning Lignosulfonate with a Conducting Polymer via Counter‐Ion Exchange for Large‐Scale Electrical Storage". Advanced Sustainable Systems 3, n.º 9 (24 de junio de 2019): 1900039. http://dx.doi.org/10.1002/adsu.201900039.

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M. Mashingaidze, Melvin y Catherine N. Shifotoka. "Copper recovery from chalcopyrite flotation plant tailings acid leach using ion exchange resin dowtm XUS 43578.00". International Journal of Engineering & Technology 7, n.º 2.23 (20 de abril de 2018): 317. http://dx.doi.org/10.14419/ijet.v7i2.23.12752.

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This study examined the feasibility of recovering copper from a sulphuric acid leach solution of chalcopyrite flotation plant tailings assaying 0.18 % copper and 0.19 % zinc using DOWTM XUS 43578.00 ion exchange resin. Zn2+cations are counter ionsto Cu2+cations during the ion exchange process. Adsorption and desorption tests were conducted on the resin with a leach solution containing26 mg Cu/L and 225 mg Zn/L,under various conditions of pH, DOWTM XUS 43578.00resin dosage, agitation time and eluant(ammonium hydroxide solution) concentration. The DOWTM XUS 43578.00resindemonstrated a high selectivity for copper over zinc, with a separation factor of 30.26 mg/g. The highcopper distribution coefficient of65L2/g2suggeststhe resin can effectively concentrate copper in leach solutions of these particular tailings.A 4M ammonium hydroxide solution yielded the highest copper recoveryat pH 3and0.6gresin dosageafter3hours of agitation. These results can be improved by a pre-treatment step to remove the zinc before the copper ion exchange process, and modifying the experiments to simulate industrial practice by having multi-stage sorption and desorption phases.

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Roux, Stéphane, Elisabeth Zékri, Bernard Rousseau, Maïté Paternostre, Jean-Christophe Cintrat y Nicolas Fay. "Elimination and exchange of trifluoroacetate counter-ion from cationic peptides: a critical evaluation of different approaches". Journal of Peptide Science 14, n.º 3 (2008): 354–59. http://dx.doi.org/10.1002/psc.951.

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Shen, Chao, Lidong Sun, Zhen Yu Koh y Qing Wang. "Cuprous sulfide counter electrodes prepared by ion exchange for high-efficiency quantum dot-sensitized solar cells". Journal of Materials Chemistry A 2, n.º 8 (2014): 2807. http://dx.doi.org/10.1039/c3ta14520d.

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Sikora, Karol, Damian Neubauer, Maciej Jaśkiewicz y Wojciech Kamysz. "Citropin 1.1 Trifluoroacetate to Chloride Counter-Ion Exchange in HCl-Saturated Organic Solutions: An Alternative Approach". International Journal of Peptide Research and Therapeutics 24, n.º 2 (12 de julio de 2017): 265–70. http://dx.doi.org/10.1007/s10989-017-9611-7.

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Liu, Jun, Chenghui Li, Yu Zhao, Aixiang Wei y Zhen Liu. "Synthesis of NiCo2S4 nanowire arrays through ion exchange reaction and their application in Pt-free counter-electrode". Materials Letters 166 (marzo de 2016): 154–57. http://dx.doi.org/10.1016/j.matlet.2015.12.062.

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Zhou, Rui-Xing, Jing-Hong Zhao y Zong-Min Wei. "Simulation and optimization of the selenium recovery process using the continuous counter-current decantation ion exchange system". Chemical Engineering Journal 191 (mayo de 2012): 386–93. http://dx.doi.org/10.1016/j.cej.2012.03.036.

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Bai, Huiwen, Ting Shen, Shixun Wang, Bo Li, Guozhong Cao y Jianjun Tian. "Controlled growth of Cu3Se2 nanosheets array counter electrode for quantum dots sensitized solar cell through ion exchange". Science China Materials 60, n.º 7 (8 de mayo de 2017): 637–45. http://dx.doi.org/10.1007/s40843-017-9037-1.

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38

Jochriem, Markus, Klaus Wurst, Holger Kopacka y Benno Bildstein. "Crystal structures of 1′-aminocobaltocenium-1-carboxylic acid chloride monohydrate and of its azo dye 1′-[2-(1-amino-2,6-dimethylphenyl)diazen-1-yl]cobaltocenium-1-carboxylic acid hexafluoridophosphate monohydrate". Acta Crystallographica Section E Crystallographic Communications 75, n.º 2 (15 de enero de 2019): 208–13. http://dx.doi.org/10.1107/s2056989019000562.

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1′-Aminocobaltocenium-1-carboxylic acid chloride, [Co(C5H6N)(C6H5O2)]Cl·H2O, (3), and its azo derivative 1′-[2-(1-amino-2,6-dimethylphenyl)diazen-1-yl]cobaltocenium-1-carboxylic acid hexafluoridophosphate, [Co(C13H14N3)(C6H5O2)]PF6·H2O (5) were obtained from cobaltocenium-1,1′-dicarboxylic acid hexafluoridophosphate by converting one carboxyl group to its chlorocarboxyl derivative followed by chloride/azide exchange, Curtius rearrangement, diazotiation and azo coupling with 2,6-dimethylaniline. Both title compounds crystallize as their monohydrates. In the crystal structure of 3, both functional groups lie in the same direction, with the Cp rings being nearly eclipsed, and participate in an extended hydrogen-bonded supramolecular network including the counter-ion and the water molecule of crystallization. Although the functional groups in 5 are somewhat further apart, bearing a greater torsion angle with the Cp rings now staggered, a similar supramolecular network is observed with not only the carboxylic acid and azo groups, but also with the more remote amino group participating in a hydrogen-bonded network, again including the counter-ion and the water molecule. The hexafluoridophosphate ion shows positional disorder. Compound 3 was refined as an inversion twin. In 5, each of the six F atoms is disordered over two sets of sites in a 1:1 ratio.

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39

Langevin, D., M. Métayer, M. Labbé, B. Pollet, M. Hankaoui, E. Sélégny y S. Roudesli. "Transport reaction through ion-exchange membranes: modelling of ligand transport by a complexing counter-ion and experiments wih ammine and polyborate ions". Desalination 68, n.º 2-3 (marzo de 1988): 131–48. http://dx.doi.org/10.1016/0011-9164(88)80050-x.

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40

Walden, Michael, Alessio Accardi, Fang Wu, Chen Xu, Carole Williams y Christopher Miller. "Uncoupling and Turnover in a Cl−/H+ Exchange Transporter". Journal of General Physiology 129, n.º 4 (26 de marzo de 2007): 317–29. http://dx.doi.org/10.1085/jgp.200709756.

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The CLC-family protein CLC-ec1, a bacterial homologue of known structure, stoichiometrically exchanges two Cl− for one H+ via an unknown membrane transport mechanism. This study examines mutations at a conserved tyrosine residue, Y445, that directly coordinates a Cl− ion located near the center of the membrane. Mutations at this position lead to “uncoupling,” such that the H+/Cl− transport ratio decreases roughly with the volume of the substituted side chain. The uncoupled proteins are still able to pump protons uphill when driven by a Cl− gradient, but the extent and rate of this H+ pumping is weaker in the more uncoupled variants. Uncoupling is accompanied by conductive Cl− transport that is not linked to counter-movement of H+, i.e., a “leak.” The unitary Cl− transport rate, measured in reconstituted liposomes by both a conventional initial-velocity method and a novel Poisson dilution approach, is ∼4,000 s−1 for wild-type protein, and the uncoupled mutants transport Cl− at similar rates.

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41

Balcar, Hynek, Naděžda Žilková, Martin Kubů, Michal Mazur, Zdeněk Bastl y Jiří Čejka. "Ru complexes of Hoveyda–Grubbs type immobilized on lamellar zeolites: activity in olefin metathesis reactions". Beilstein Journal of Organic Chemistry 11 (4 de noviembre de 2015): 2087–96. http://dx.doi.org/10.3762/bjoc.11.225.

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Hoveyda–Grubbs type catalysts with cationic tags on NHC ligands were linker-free immobilized on the surface of lamellar zeolitic supports (MCM-22, MCM-56, MCM-36) and on mesoporous molecular sieves SBA-15. The activity of prepared hybrid catalysts was tested in olefin metathesis reactions: the activity in ring-closing metathesis of citronellene and N,N-diallyltrifluoroacetamide decreased in the order of support MCM-22 ≈ MCM-56 > SBA-15 > MCM-36; the hybrid catalyst based on SBA-15 was found the most active in self-metathesis of methyl oleate. All catalysts were reusable and exhibited low Ru leaching (<1% of Ru content). XPS analysis revealed that during immobilization ion exchange between Hoveyda–Grubbs type catalyst and zeolitic support occurred in the case of Cl− counter anion; in contrast, PF6 − counter anion underwent partial decomposition.

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42

Magnico, Pierre. "Electro-Kinetic Instability in a Laminar Boundary Layer Next to an Ion Exchange Membrane". International Journal of Molecular Sciences 20, n.º 10 (14 de mayo de 2019): 2393. http://dx.doi.org/10.3390/ijms20102393.

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The electro-kinetic instability in a pressure driven shear flow near an ion exchange membrane is considered. The electrochemical system, through which an electrical potential drop is applied, consists in a polarization layer in contact with the membrane and a bulk. The numerical investigation contained two aspects: analysis of the instability modes and description of the Lagrangian transport of fluid and ions. Regarding the first aspect, the modes were analyzed as a function of the potential drop. The analysis revealed how the spatial distribution of forces controls the dynamics of vortex association and dissociation. In particular, the birth of a counter-clockwise vortex between two clockwise vortices, and the initiation of clusters constituting one or two envelopes wrapping a vortex group, were examined. In regards to the second aspect, the trajectories were computed with the fourth order Runge Kutta scheme for the time integration and with the biquadratric upstream scheme for the spatial and time interpolation of the fluid velocity and the ion flux. The results for the periodic mode showed two kinds of trajectories: the trochoidal motion and the longitudinal one coupled with a periodic transverse motion. For the aperiodic modes, other mechanisms appeared, such as ejection from the mixing layer, trapping by a growing vortex or merging vortices. The analysis of the local velocity field, the vortices’ shape, the spatial distribution of the forces and the ion flux components explained these trajectories.

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43

Trifi, Ikhlass Marzouk, Beyram Trifi, Sirine Ben Ayed y Béchir Hamrouni. "Removal of phosphate by Donnan dialysis coupled with adsorption onto calcium alginate beads". Water Science and Technology 80, n.º 1 (1 de julio de 2019): 117–25. http://dx.doi.org/10.2166/wst.2019.256.

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Abstract In this study the removal of phosphates from solution by Donnan dialysis and by adsorption onto calcium alginate beads were studied separately and then together. This hybrid process was conducted in order to benefit from each process, and it is an original and new combination. First, the Donnan dialysis process was performed with different parameters: the type of counter-ion, the concentration of the counter-ion, the initial phosphate concentration, the pH of the solution and the choice of anion-exchange membranes. Donnan dialysis achieved 68% and 12.5% phosphorus removal with AMX and AFN membranes respectively. Then a preliminary study into the adsorption of phosphate onto calcium alginate beads was carried out. A full factor design was applied in order to determine the effect of the main parameters and their mutual interactions for the adsorption process. The removal of phosphate onto calcium alginate beads reached 82.5%. Finally, coupling Donnan dialysis with adsorption onto calcium alginate beads for the removal of phosphate reached 89.5% with the AMX membrane. This hybrid process can be considered to be a solution for improving the contact time and for enhancing the removal of phosphate by 10% compared to adsorption onto calcium alginate.

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44

Cardoso, Simão P., Tiago L. Faria, Eduarda Pereira, Inês Portugal, Cláudia B. Lopes y Carlos M. Silva. "Mercury Removal from Aqueous Solution Using ETS-4 in the Presence of Cations of Distinct Sizes". Materials 14, n.º 1 (22 de diciembre de 2020): 11. http://dx.doi.org/10.3390/ma14010011.

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The removal of the hazardous Hg2+ from aqueous solutions was studied by ion exchange using titanosilicate in sodium form (Na-ETS-4). Isothermal batch experiments at fixed pH were performed to measure equilibrium and kinetic data, considering two very distinct situations to assess the influence of competition effects: (i) the counter ions initially in solution are Na+ and Hg2+ (both are exchangeable); (ii) the initial counter ions in solution are tetrapropylammonium (TPA+) and Hg2+ (only Hg2+ is exchangeable, since TPA+ is larger than the ETS-4 micropores). The results confirmed that ETS-4 is highly selective for Hg2+, with more than 90% of the mercury being exchanged from the fluid phase. The final equilibrium attained under the presence of TPA+ or Na+ in solution was very similar, however, the Hg2+/Na+/ETS-4 system in the presence of Na+ required more 100 h to reach equilibrium than in the presence of TPA+. The Hg2+/Na+/ETS-4 system was modelled and analyzed in terms of equilibrium (mass action law) and mass transfer (Maxwell–Stefan (MS) formalism). Concerning equilibrium, no major deviations from ideality were found in the range of studied concentrations. On the other hand, the MS based model described successfully (average deviation of 5.81%) all kinetic curves of mercury removal.

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45

Yi, Shixiong, Gang Sun y Fangyin Dai. "Removal and separation of mixed ionic dyes by solvent extraction". Textile Research Journal 88, n.º 14 (20 de abril de 2017): 1641–49. http://dx.doi.org/10.1177/0040517517705631.

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To reduce environmental pollution from dyeing wastewater, reverse micelles were prepared and used for the removal and separation of anionic Color Index (CI) Reactive Yellow 3 and cationic CI Basic Red 14 in mixed dye aqueous solution. The effect of the amount of dye and surfactant on removal rates of dyes was investigated. An ion-exchange reaction model was used to fit the experimental data. Ultraviolet-visible absorption spectra were employed to evaluate the state of dyes in mixed dye aqueous solution during the removal process. In addition, the removed dyes were recovered by back extraction and reused for dyeing fabrics. The results obtained indicated that the removal of dyes was increased with increasing the amount of surfactants, while the dye concentration exhibited the reverse trend. The dye extraction process could be described by the ion-exchange reaction equations. The mixed dyes could be removed and separated for the attractive force between dyes and the counter ionic surfactant. The mixed dyes were separated and recovered, which exhibited a good dyeing property.

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46

Moldoveanu, G. A. y V. G. Papangelakis. "An overview of rare-earth recovery by ion-exchange leaching from ion-adsorption clays of various origins". Mineralogical Magazine 80, n.º 1 (febrero de 2016): 63–76. http://dx.doi.org/10.1180/minmag.2016.080.051.

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AbstractContinuous development of advanced technologies has created increasing demand for rare-earth elements (REE), with global emphasis on identifying new alternate sources to ensure adequate supply. Ore deposits containing physically adsorbed lanthanides are substantially lower grade than other REE deposit types; however, the low mining and processing costs make them economically attractive as sources of REE. To evaluate the commercial potential for the recovery of REEs from ion-adsorption deposits in a systematic manner, a standardized procedure for REE leaching was developed previously. Using this procudure it was found that, regardless of variations in ore origin and REE content, all REE consistently reached peak extraction levels under ambient conditions with fast kinetics. Various techniques to improve the REE extraction through process variations were also investigated: it was found that decreasing the L:S ratio, re-using leachate on fresh ores and counter-current leaching were all capable of increasing REE concentrations in the resultant leachate, albeit at the expense of REE extraction levels. In addition, the water content trapped in the leached material was found to contain significant amounts of REE and residual lixiviant requiring thorough washing of the solid residue.

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47

Ghilane, Jalal, Gaëlle Trippe-Allard y Jean Christophe Lacroix. "Grafting of imidazolium ion-terminated layer using electrochemical reduction of diazonium: Redox active counter anion exchange within the layer". Electrochemistry Communications 27 (febrero de 2013): 73–76. http://dx.doi.org/10.1016/j.elecom.2012.11.003.

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48

Schöffler, Anne L., Ata Makarem, Frank Rominger y Bernd F. Straub. "Dinuclear thiazolylidene copper complex as highly active catalyst for azid–alkyne cycloadditions". Beilstein Journal of Organic Chemistry 12 (21 de julio de 2016): 1566–72. http://dx.doi.org/10.3762/bjoc.12.151.

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A dinuclear N-heterocyclic carbene (NHC) copper complex efficiently catalyzes azide–alkyne cycloaddition (CuAAC) “click” reactions. The ancillary ligand comprises two 4,5-dimethyl-1,3-thiazol-2-ylidene units and an ethylene linker. The three-step preparation of the complex from commercially available starting compounds is more straightforward and cost-efficient than that of the previously described 1,2,4-triazol-5-ylidene derivatives. Kinetic experiments revealed its high catalytic CuAAC activity in organic solvents at room temperature. The activity increases upon addition of acetic acid, particularly for more acidic alkyne substrates. The modular catalyst design renders possible the exchange of N-heterocyclic carbene, linker, sacrificial ligand, and counter ion.

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49

Lovett, Gary M., Steven E. Lindberg, Daniel D. Richter y Dale W. Johnson. "The effects of acidic deposition on cation leaching from three deciduous forest canopies". Canadian Journal of Forest Research 15, n.º 6 (1 de diciembre de 1985): 1055–60. http://dx.doi.org/10.1139/x85-171.

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Canopy leaching or retention of all major ions was determined for three deciduous forests in eastern Tennessee that are currently receiving wet and dry acidic deposition. For all three canopies, the retention of atmospherically deposited cations (H+ and [Formula: see text]) exceeded retention of deposited anions [Formula: see text] on a charge-equivalent basis. Charge balance was maintained by ion exchange between the deposited cations and K+, Ca2+, and Mg2+ on the canopy surfaces. It was found that 40–60% of the leaching of K+, Ca2+, and Mg2+ from these canopies results from this exchange process, with the remainder attributable to coleaching with plant-derived anions. Because the cation exchange can be largely attributed to retention of deposited H+, we interpret it as a measure of the acidic deposition effect on foliar cation leaching. Dry deposition was found to be an important input for most of the major cations and anions. The data indicate that organic anions may be important counter ions to cation leaching, especially in the absence of acidic deposition, and that acid–base reactions in the canopy can obscure the true H+-exchange reactions between the deposition and the canopy.

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50

Asante-Sackey, Dennis, Sudesh Rathilal, Lingham V. Pillay y Emmanuel Kweinor Tetteh. "Ion Exchange Dialysis for Aluminium Transport through a Face-Centred Central Composite Design Approach". Processes 8, n.º 2 (30 de enero de 2020): 160. http://dx.doi.org/10.3390/pr8020160.

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An ion exchange dialysis (IED) is used in the recovery of aluminium from residue. In this paper, the face-centred central composite design (FC-CCD) of the response surface methodology (RSM) and desirability approach is used for experimental design, modelling and process optimization of a counter flow IED system. The feed concentration, feed flowrate, sweep flowrate and sweep concentration were selected as the process variables, with the Al transport across a Nafion 117 membrane as the target response. A total of 30 experimental runs were conducted with six centre points. The response obtained was analysed by analysis of variance (ANOVA) and fitted to a second-order polynomial model using multiple regression analysis. The actual R2 and standard deviation of the model are 0.9548 and 0.2932, respectively. Depending on the time zone of reference (24 h or 32 h), the highest enrichment of >1.50 was achieved. The designed variables were numerically optimized by applying the desirability function to achieve the maximum Al transport. The optimised condition values were found to be a feed concentration of 1600 ppm, feed flowrate of 61.76%, sweep flowrate of 37.50% and sweep concentration of 0.75 N for the 80% target response at 32 h. Overall, the model can be used to effectively predict Al recovery using the designed system.

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