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Greener and Sustainable Approach for the Synthesis of Commercially Important Epoxide Building Blocks Using Polymer-Supported Mo(VI) Complexes as Catalysts
Published in Arup K. Sengupta, Ion Exchange and Solvent Extraction, 2017
Misbahu Ladan Mohammed, Basudeb Saha
Polymer-supported catalysts are made by immobilizing a robust polymer support with an active species either by forming chemical bonds or through physical interactions such as hydrogen bonding or donor-acceptor interactions. Suspension polymerization is one of the most popular and effective methods of synthesizing polymers in spherical or bead form. The polymerization reaction is of two types depending on the nature of the monomers. For instance, inverse suspension polymerization is employed for hydrophilic monomers such as acrylamide using hydrocarbon or chlorinated hydrocarbon as the bulk liquid phase in the reaction.42 However, water is used as the bulk liquid phase in suspension polymerization involving hydrophobic monomers such as styrene. The polymer resins intended for use as support are normally cross-linked using a bi-functional co-monomer such as divinylbenzene (DVB) to form an infinite network.43 The uniform shape and sizes of the polymer beads prepared by the suspension polymerization method depend on the shape of the reactor, impeller diameter, stirring speed, porogen, and other reaction conditions.44 Basically, there are two factors that are responsible for the internal porous structure of polymer beads. These include the amount of crosslinking present and the type of organic solvent or porogen incorporated into the polymer resin. The former determines the level of swelling of the polymer, while the latter creates the pores and influences the pore size, pore volume, and surface area of the polymer particles.44,45
Effect of Chemical Structure on Polymer Properties
Published in Anil Kumar, Rakesh K. Gupta, Fundamentals of Polymer Engineering, 2018
Among all exchangers, the most important are organic ion exchangers, which are cross-linked polymeric gels. When the polymer matrix carries ions such as −SO31−, –COO1–, PO32−,AsO32−, and so forth, it is called a cation exchanger; when it has −NH41+,−NH22+, −N+,−S+, and so forth, it is called an anion exchanger. The organic material most commonly in use is a copolymer gel of styrene and divinyl benzene (DVB), and the general-purpose resin contains about 8%–12% of the latter. As the DVB content is reduced, the degree of cross-linking reduces, and at around 0.25% DVB, the polymeric gel swells strongly to give a soft, gelatinous material. As DVB is increased (at about 25%), the polymer swells negligibly and is a mechanically tough material.
Molten salt oxidation and process analysis of anionic exchange resin in Na2CO3-K2CO3 melt
Published in Journal of Nuclear Science and Technology, 2022
Yang-Hai Zheng, Yun Xue, Yong-De Yan, Xue-Ze Wang, Fu-Qiu Ma, Mi-Lin Zhang, Tai-Qi Yin, Zi-Qi Kou, Hai-Yun Bai, Jian-Peng Liu
Nuclear power is regarded as an alternative of fossil fuels and get a significant development due to the characteristic of clear and high efficiency. However, the rapid development of the nuclear industry has also brought many environmental problems, especially the treatment of the waste resin with low radioactivity. The waste resins with low radioactivity were generated by the fresh resins exchanging radioactivity ions with process water. The fresh resins used in ions-exchanging method include two kinds of resins: (1) acidic cationic ion-exchange resins, which have the structure of a styrene-divinylbenzene (ST-DVB) copolymer with a functional group of -SO3-H+. The ST-DVB is a copolymer synthesized with styrene as a monomer and divinylbenzene as a crosslinking agent. The content of divinylbenzene is usually considered as the degree of crosslinking of the copolymer. (2) basic anionic ion-exchange resins with the matrix of an ST-DVB, which is a copolymer with a functional group of -N(CH3)3-OH−. During the ion-exchanging process, the ions H+ and OH− are exchanged for the Co2+, Sr2+, Cs+ and U2O72- in the waste water. After exchanging a certain amount of radioactive or hazardous contaminants, the spent resins may be harmful to the health of public and environment [1,2]. To protect the environment out from the pollution of waste resins, many treatment methods were generated and conducted, such as incineration, solidification and wet oxidation. Compared with other treatment technology, the incineration can destroy spent resins completely, which has been well recognized as the most available technology for disposal of organic wastes [3]. The main disadvantage of incineration is that exhaust gas requires secondary treatment [4–6]. Moreover, the temperature of incineration is usually higher than the volatilization temperature of the radioactive and toxic metals, which will be detrimental to the environment. During incineration, the nitrogen and sulfur in the spent resins will be converted into N2O/NO/NO2 and SO2/SO3, which contribute to acid rain. Moreover, during the pyrolysis and incineration process, the incomplete oxidation of organic resins may generate a lot of unburned hydrocarbons, which can react with NOx emissions in the presence of sunlight to produce ozone [7]. Thus, the incineration requires additional processes and equipment to eliminate the hazardous gases emissions, which makes the treatment steps complex and expensive [8].