• Journal of the Korean institute of surface engineering
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• v.51 no.5
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• pp.257-262
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• 2018

Cesium lead halide perovskite quantum dots (QDs) have recently emerged as highly promising opto-electronic materials. Despite the relative facile anion exchange reactions in cesium lead halide perovskite QDs, in depth study of the anion exchange reactions such as reaction kinetics are required that can provide insight into the crystal transformation in the cesium lead halide perovskite QDs. Herein, we investigated the anion exchange reaction from $CsPbI_3$ QDs to $CsPbBr_3$ QDs with varying the particle size of the starting $CsPbI_3$ QDs. By characterizing the PL spectra in the anion exchange reaction process, we observed that discontinuous PL peak shifts during I-to-Br anion exchange reaction in starting $CsPbI_3$ QDs over a critical size. Origin of the discontinuous I-to-Br anion exchange kinetics are mainly due to thermodynamically unstable nature of the $CsPb(Br/I)_3$ alloy QDs.

• Bulletin of the Korean Chemical Society
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• v.28 no.5
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• pp.721-722
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• 2007

• Applied Chemistry for Engineering
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• v.21 no.6
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• pp.621-626
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• 2010

Anion exchange membranes can be used for reverse electrodialysis for electric energy generation, and capacitive deionization for water purification, as well as electrodialysis for desalination. In this study, anion exchange membranes of poly((vinylbenzyl) trimethylammonium chloride-2-hydroxyethyl methacrylate)/poly(vinyl alcohol) were prepared through the polymerization of (vinylbenzyl)trimethylammonium chloride and 2-hydroxyethyl methacrylate in aqueous poly(vinyl alcohol) solutions, esterification with glutaric acid, and cross-linking reaction with glutaraldehyde. We investigated electrochemical properties for the anion exchange membranes prepared according to experimental conditions. Ion exchange capacity and electrical resistance for the membranes were changed with a variation in the monomer ratio in polymerization. Water uptake and conductivity for the membranes decreased with an increase in the content of glutaric acid in esterification. The change in the time of crosslinking reaction with the formed film and glutaraldehyde affected electrochemical properties such as water uptake, conductivity, or transport number for the membranes. Chronopotentiometry and limiting current density for the anion exchange membranes prepared were measured.

• Journal of Environmental Science International
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• v.9 no.2
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• pp.165-171
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• 2000

A kinetic study for anion exchange was performed for commercially available Cl- type anion exchange resin in use to remove nitrate in water. The obtained results from the batch reactor were applied to the Langmuir and Freundlich models. The constants for Lagmuir model were qmax =29.82 and b=0.202, and for Freundlich model were K=5.509 and n=1.772. Langmuir model showed betterfit than Frendlich model for the experimental results. Ion exchange reaction rate was also calculated and the the approximate first-order reaction, rate constant k1 was 0.16 L/mg.hr. Effective diffusion coefficient was obtained in the range from $9.67$\times$10^{-8} cm^2/sec$ for initial concentration change, and from $6.09$\times$10^{-7} to 3.98$\times$10^{-6} cm^2/sec$ for reaction temperature change. Activation energy during the diffusion was calculated as 26 kcal/mol.

• Applied Chemistry for Engineering
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• v.29 no.5
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• pp.489-496
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• 2018

Fuel cells are seen as eco-friendly energy resources that convert chemical energy into electrical energy. However, proton exchange membrane fuel cells (PEMFCs) have problems such as the use of expensive platinum catalysts for the reduction of conductivity under high temperature humidification conditions. Thus, an anion exchange membrane fuel cell (AEMFC) is attracting a great attention. Anion exchange fuel cells use non - Pt catalysts and have the advantage of better efficiency because of the lower activation energy of the oxygen reduction reaction. However, there are various problems to be solved including problems such as the electrode damage and reduction of ion conductivity by being exposed to the carbon dioxide. Therefore, this mini review proposes various solutions for different problems of anion exchange fuel cells through a wide range of research papers.

• Journal of the Korean Chemical Society
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• v.9 no.1
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• pp.23-28
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• 1965

Halogen exchanges between benzyl chloride and chloride ion have been studied in 90% ethanol-water mixture, and activation parameters in the exchange reaction have been determined; ${\Delta}H^{\neq}$ = 18. 50 Kcal and ${\Delta}S^{\neq}$ = -22. 09 e. u. Results indicated that the reaction proceeded via a typical bimolecular mechanism. The importance of nucleophilic ability of attacking anion in $S_N2$ process has been stressed giving some experimental evidence. The order of reactivity of halides in the exchange reaction is better explained with the Swain's nucleophilic parameter than with the bond dissociation energies.

• Membrane Journal
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• v.28 no.5
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• pp.326-331
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• 2018

Crosslinking of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) anion exchange membranes, which can be used for capacitive deionization (CDI), was investigated. PPO Anion exchange polymer was prepared through bromination and amination reaction steps and crosslinked with bisphenol A diglycidylether (BADGE), m-phenylenediamine (m-PDA), and hexamethylenediamine (HMDA). The gelation time by crosslinking was short in the order of HMDA > m-PDA > BADGE. The anion exchange membranes crosslinked at room temperature over a certain amount of crosslinking agent did not dissolve in an aprotic solvent such as 1-methylpyrrolidone (NMP) and the chemical durability of their membranes to organic solvent increased. The ion exchange capacity and water uptake of anion exchange membranes crosslinked with different crosslinker (BADGE) contents were measured and compared. The CDI performance of the crosslinked PPO anion exchange membrane immersed in the HMDA solution was almost the same as that of the non - crosslinked membrane except for the initial stage of the adsorption step.

• Polymer(Korea)
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• v.39 no.1
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• pp.157-164
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• 2015

In this study, we synthesized poly(vinylimidazole-co-trifluoroethylmethacrylate-co-divinylbenzene) (PVTD) copolymer and introduced functional group through quaternization reaction for removing nitrate from drinking water. Also, optimizing conditions (reaction time, reaction temperature and functionalized agents concentration) for introducing the functional group were confirmed. The basic properties such as water uptake, swelling ratio, electrical resistance, ion exchange capacity and anion permselectivity for removing nitrate from drinking water were measured. The optimal values of water uptake, electrical resistance and ion exchange capacity of synthesized anion exchange membrane were 51.2%, $5.4{\Omega}{\cdot}cm^2$, and 1.04 meq/g, respectively.

• Applied Chemistry for Engineering
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• v.17 no.3
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• pp.303-309
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• 2006

In this study, functional anion-exchange membranes have been prepared and characterized to improve the permeation fluxes of the anion and urea for peritoneum dialysis. They were prepared by UV and radiation graft polymerization methods. The separation-membrane prepared by UV graft polymerization showed the highest grafting degree when HEMA and VBTAC were mixed by 1:2 ratio. However, the grafting degree decreased slightly at compositions above the 1:2 ratio because of the disruption of UV penetration caused by build-up of homopolymer. In the case of photo-initiator, the grafting degree increased up to 0.2 wt%, above which it decreased to a small extent. For the two membranes prepared by radiation graft polymerization, the VBTAC/HEMA membrane showed 96% grafting degree for 6 h reaction time and the GMA membrane showed over 100% grafting degree for 2 h reaction time. Anion-exchange membranes were prepared with 113% grafting degree and with DEA and TEA exchange groups. The DEA membrane showed the conversion degree of 70% in 4 h reaction time while the TEA membrane showed 30% in 2 h reaction time. The prepared anion-exchange membranes were permeable to only anions and urea, but not cations.

• Polymer(Korea)
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• v.36 no.5
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• pp.564-572
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• 2012

A terpolymer of vinylbenzyl chloride-co-ethyl methacrylate-co-styrene (VBC-EMA-St) was prepared for membrane capacitive deionization (MCDI) by radical polymerization and amination reaction of various amination times. Nonfluoro aminated VBC-EMA-St anion-exchange membranes were characterized by Fourier transform infrared (FTIR) spectrometry. Molecular weight, polydispersity and thermal stability were obtained by gel permeation chromatography (GPC) and thermogravimetric analysis (TGA). The basic properties such as water uptake, ion exchange capacity, electrical resistance and CDI charge-discharge current were measured. The optimal values of ion exchange capacity, water uptake, electrical resistance and molecular weight of synthesized anion-exchange membrane were 1.69 meq/g, 23.7%, 1.61 ${\Omega}{\cdot}cm$ and $3.4{\times}10^4$ g/mol, respectively. As compared with conventional membrane, the pattern of cyclic charge-discharge current of synthesized anion-exchange membrane indicated efficient electrosorption and desorption.