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Membrane Materials for Ion Exchange Membrane Fuel Cell Applications
Published in Stephen Gray, Toshinori Tsuru, Yoram Cohen, Woei-Jye Lau, Advanced Materials for Membrane Fabrication and Modification, 2018
Yubin He, Jianqiu Hou, Tongwen Xu
IEMs are typically composed of hydrophobic substrates, immobilized ion conducting groups and movable counter ions. Depending on the type of ionic groups, IEMs are broadly classified into CEMs and anion exchange membranes (AEMs). Naturally, the ion pair between counter ions and ion conducting groups will dissociate after the penetration of sufficient water molecules, releasing cations or anions for the transfer of corresponding ions. The common functional moiety in CEMs is a sulfonic acid group, while that in AEMs is quaternary ammonium cation.
Interfacial Catalysis at Oil/Water Interfaces
Published in Alexander G. Vdlkdv, Interfacial Catalysis, 2002
In addition to consideration of the structure-activity relationships, the criteria for selecting a PTC catalyst usually include the following features: (1) stability, (2) cost and availability, (3) removal, recovery, and recycling, (4) toxicity, and (5) waste treatment, etc. The tetrabutylammonium cation is the most widely used quaternary ammonium cation. It is commercially available in a wide variety of anions at moderate cost and has a unique application in tri-liquid-phase catalysis. It can also be easily separated and recovered by extraction, then recycled. Methyltributylammonium cation will become a popular catalyst due to its high reactivity in transfer rate limited PTC reactions, its lower toxicity than most quaternary ammonium cations, and its low price. Methyltrioctylammonium cation is also commercially popular and is organophilic and anion activating enough to catalyze most intrinsic reaction rate limited PTC reactions and is accessible enough to catalyze most transfer rate limited PTC reactions. In comparison with quaternary ammonium salts, quaternary phosphonium salts are generally more thermally stable and more active under neutral or acidic conditions, but less stable under alkaline conditions. Although they have been used in a variety of PTC reactions, the greater cost compared to quaternary ammonium salts limits their industrial applications. Toxic quaternary arsonium salts are used mainly for comparative processes. Tetraphenylarsonium salts are useful for PTC analytical titration of highly organophilic unsaturated compounds [3]. The triphenylsulfonium cation is stable under strong alkaline conditions and is effective for catalyzing the PTC displacement of 1-bromo-octane with NaCN,NaOPh,KSCN, and KI [107].
Regulation of Osmolytes Syntheses and Improvement of Abiotic Stress Tolerance in Plants
Published in Hasanuzzaman Mirza, Nahar Kamrun, Fujita Masayuki, Oku Hirosuke, Tofazzal M. Islam, Approaches for Enhancing Abiotic Stress Tolerance in Plants, 2019
Ambuj Bhushan Jha, Pallavi Sharma
Quaternary ammonium compounds, which are quaternary ammonium cation salts, act as osmolytes and alleviate abiotic stress in plants. Among several quaternary ammonium compounds, GB is one of the most widely found osmolytes in plants under drought, salinity, extreme temperature and metal stress (Hanson et al., 1991; Guo et al., 2009; Lokhande and Suprasanna, 2012). Exogenously applied GB protects against harmful effects of abiotic stresses. GB counteracted the water stress-induced decrease in head diameter, achene number, weight, yield and oil yield in sunflower plants (Hussain et al., 2008). Its application reduced the inhibitory effects of water stress on net CO2 assimilation rate, sub-stomatal CO2 concentration and transpiration rate in sunflower plants (Iqbal et al., 2009). Under salt stress, exogenously supplied GB reduced membrane injury, improved uptake of K+, growth and enhanced chlorophyll contents in V. faba (Gadallah, 1999), reduced Na+ accumulation, maintained shoot K+ concentration and improved salt tolerance in rice plants (Harinasut et al., 1996; Lutts, 2000), improved growth, net photosynthesis, leaf water conten t and the apparent quantum yield of photosynthesis in maize plants (Yang and Lu, 2005), improved growth parameters, free amino acids, photosynthetic pigments, proline, phenolic and total soluble carbohydrate contents, yield and yield components in sunflower (Bakhoum and Sadak, 2016). The fatty acid profile of sunflower oil also exhibited some alterations under the influence of salinity and GB treatments (Bakhoum and Sadak, 2016). GB increased yield (about 40%) of tomato plants grown under salt stress or high temperatures (Mäkelä et al., 1999, 2000). A cryoprotective effect of GB on membranes and enzymes has been reported (Gorham, 1995). Exogenous supply of GB has been shown to improve freezing stress tolerance of plants (Allard et al., 1998; Sakamoto and Murata, 1998; Farooq et al., 2008). GB enhanced low-temperature tolerance in tobacco and strawberry (Rajashekar et al., 1999; Holmström et al., 2000). In Arabidopsis plants, GB reduced the freezing temperature from −3.1 to −4.5˚C (Xing and Rajashekar, 2001). GB also protected mungbean against Cd-induced oxidative stress by decreasing H2O2 concentration and lipid peroxidation and enhancing the antioxidant defense and methylglyoxal detoxification system (Hossain and Fujita, 2010).
Development of Tracer Particles for Positron Emission Particle Tracking
Published in Nuclear Science and Engineering, 2023
Thomas Leadbeater, Andy Buffler, Michael van Heerden, Ameerah Camroodien, Deon Steyn
Chelex-100 anion ion exchange resins30,32,42 and gamma-phase alumina (γ-Al2O3) have been demonstrated to be particularly efficient in producing 18F-based resin cores.43–45 At PEPT Cape Town,46 the strong-base anion exchange resins Purolite A200 and A870 are used. These consist of very small porous beads with quaternary ammonium cation functional groups attached to the styrene divinylbenzene copolymer lattice. These anion exchange resins are typically in chloride form where chloride is the counterion to be exchanged with 18F−. However, because the affinity of the 18F− ion to the functional groups is predominantly weaker than the Cl⁻ ion, the resin particles must first be converted into fluoride or hydroxide form. The conversion is achieved by rinsing the resin slurry with 8 to 10 bed volumes of 1 M KF solution to displace the Cl− counterions with F− ions before rinsing with 10 bed volumes of deionized water to remove the K+ and any unbound F− ions. Radiolabeling proceeds as described above, starting from 18F− ions dissolved in pure water, with the resin substrate undergoing further physical modification after production to match particle properties as detailed above.
Preparation and characterization of surfactant loaded clays as drug adsorbents
Published in Journal of Dispersion Science and Technology, 2023
Elif Çalışkan Salihi, R. Yeşim Cantürk Talman, Sinem Göktürk
Surfactant loaded clays were prepared using anionic and cationic surfactants (SDS, DBSA, DTAB, DPC; see Table 1 for molecular structures) for the modification of BENT using a basic and one-pot method in this study. SDS is an organosulfate salt consists of a tail with 12 carbons and a sulfate group. It is an anionic surfactant with its hydrophobic moiety and the polar headgroup. DBSA which is also an anionic surfactant is a member of the dodecylbenzenesulfonic acids where one of the hydrogens of the phenyl ring is substituted by a dodecyl group. DTAB is a quaternary ammonium cation which has one dodecyl and three methyl substituents around the central nitrogen. It is a cationic surfactant and a bromide salt. DPC is also a cationic surfactant and a pyridine compound with nonpolar hydrocarbon tale of dodecyl group. All the surfactants used have the dodecyl group as hydrophobic tale in common. Characterization data of the surfactant loaded clays were given and discussed below.
Interface engineering of quaternary ammonium phosphotungstate for efficient oxidative desulfurization of high-sulfur petroleum coke
Published in Petroleum Science and Technology, 2023
Jiahong Gong, Huanhuan Xu, Jixing Liu, Hui Liu, Mingqing Hua, Ning Yang, Peiwen Wu, Huaming Li, Wenshuai Zhu
In summary, quaternary ammonium phosphotungstate ionic liquids with different carbon chain lengths were developed to catalyze oxidative desulfurization of high-sulfur petroleum coke and thiophene sulfides. It was found that the length of the alkyl carbon chain in the quaternary ammonium cation can significantly affect the activity of the catalyst. The results showed that C4@HPA/H2O2 had excellent performance in ODS of HSPC under mild conditions. The sulfur content in HSPC could be reduced from 4.46 wt.% to 2.76 wt.% at 70 °C for 5 h. According to the results of FT-IR, XRD and XPS, parts of the sulfide in HSPC were oxidized to sulfone, sulfoxide and sulfate, while only sulfate could be removed. Further simulation ODS experiments with five thiophene sulfides showed that the most complex structure 4-MDBT was the most difficult in ODS and its sulfate conversion only has 4.61%.