Ion exchange, research

Sata, T. (1986) Recent trends in ion-exchange research. Pure and Applied Chemistry, 58, 1613. 

Hydrolysis of zeolites gives rise to a range of impurity species in both the solution and zeolite phases, which may interfere with the study of binary metal cation exchange. Up to now, most zeolite ion exchange research has been carried out using initially the sodium forms of the zeolites. In this form, zeolites hydrolyse by taking up hydronium ions from the water, viz.. 

Zeohtes (qv), ion-exchange compounds, have been researched to some extent and have been proposed to improve NPN utilisation (25). However, no improvement in NPN utilisation was found with lambs fed seoHtes (26). 

Research has shown that ascorbic acid can be produced from hulls of immature walnuts by extracting the hull with 0.2% sulfur dioxide solutions, and purifyiag the extract by adsorption on and elution from anion-exchange resias (see Ion exchange). Eluates from the anion-exchange step are concentrated, purified by organic solvent fractionations, decolorized, and crystallized (35). 

A hst of polyol producers is shown in Table 6. Each producer has a varied line of PPO and EOPO copolymers for polyurethane use. Polyols are usually produced in a semibatch mode in stainless steel autoclaves using basic catalysis. Autoclaves in use range from one gallon (3.785 L) size in research faciUties to 20,000 gallon (75.7 m ) commercial vessels. In semibatch operation, starter and catalyst are charged to the reactor and the water formed is removed under vacuum. Sometimes an intermediate is made and stored because a 30—100 dilution of starter with PO would require an extraordinary reactor to provide adequate stirring. PO and/or EO are added continuously until the desired OH No. is reached the reaction is stopped and the catalyst is removed. A uniform addition rate and temperature profile is required to keep unsaturation the same from batch to batch. The KOH catalyst can be removed by absorbent treatment (140), extraction into water (141), neutralization and/or crystallization of the salt (142—147), and ion exchange (148—150). 

The Zeolite Researchers List Catalysis, ion-exchange and separation -... 

List of researchers in the field of zeolites (including URLs and e-mail-adresses). Subfield Catalysis, ion-exchange and separation, http //w w w. tn. utwente. nl/cdr/S taff/Haral. 

A sulfonated ion exchanger catalyst (Research Institute of Synthetic Resins and Varnishes, Pardubice, Czechoslovakia) was a macroreticular styrene-divinylbenzene copolymer containing 25% divinylbenzene and 2.4 meq/g of —SO3H groups. It was dried prior to using at 90°C/14 Torr. The BET surface area, determined in a dry state, was 49 m2/g, and the mean pore size was around 100 A. 

An overview is presented of plutonium process chemistry at Rocky Flats and of research in progress to improve plutonium processing operations or to develop new processes. Both pyrochemical and aqueous methods are used to process plutonium metal scrap, oxide, and other residues. The pyrochemical processes currently in production include electrorefining, fluorination, hydriding, molten salt extraction, calcination, and reduction operations. Aqueous processing and waste treatment methods involve nitric acid dissolution, ion exchange, solvent extraction, and precipitation techniques. 

Research should continue on traditional separation methods. For example, there is a continuing need for more selective extraction agents for liquid-liquid and ion-exchange extractions. High-temperature processes that use liquid metals or molten salts as extraction agents should have potential in nuclear fuel reprocessing and... 

Providing an ion exchanger with a sufficient number of redox groups so that conduction can occur by a relay-type redox-change mechanism. Examples are hydroquinone-derived redox polymers and polyvinyl polymers with a tetrathia-fulvalene, ferrocene, or carbazole group, which have been found useful for research and analytical applications. 

Procedure As Phleum pretense produces much more pollen thanElieracium species and previous work, I have focused my limited efforts in this area of research on P. pratense. The author still uses simple ion-exchange chromatography to extract pigments and in P. pratense, most of these are flavonoids. 

Spedding, F. H. and Powell, J. E. (1956). Ion exchange methods of separating rare earths, page 37 in Rare Earths in Biochemical and Medical Research A Conference Sponsored by the Medical Division, Oak Ridge Institute of Nuclear Studies, October 1955, Report No. ORINS-12, Kyker, G. C. and Anderson, E. B., Eds. (Office of Technical Services, Washington). 

The disadvantages described above in terms of the irreversibility of the polyion response stimulated further research efforts in the area of polyion-selective sensors. Recently, a new detection technique was proposed utilizing electrochemically controlled, reversible ion extraction into polymeric membranes in an alternating galvanostatic/potentiostatic mode [51]. The solvent polymeric membrane of this novel class of sensors contained a highly lipophilic electrolyte and, therefore, did not possess ion exchange properties in contrast to potentiometric polyion electrodes. Indeed, the process of ion extraction was here induced electrochemically by applying a constant current pulse. 

Solvent polymeric membranes conventionally consist of ionophore, ion exchanger, plasticizer, and polymer. The majority of modem polymeric ISEs are based on neutral carriers, making the ionophore the most important membrane component. Substantial research efforts have focused on the development of highly selective ionophores for a variety of analytes [3], Some of the most successful ionophores relevant to biomedical applications are depicted in Fig. 4.1. 

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