Extractants chemical regeneration

Chemical regeneration of extractants to offset degradation losses during operation. 

Extractions with caustic and/or isopropanol that can desorb a fraction of macromolecular compounds (chemical regeneration). 

Continuous electrodeionization technology uses mixed bed ion exchange resins and selectively permeable membranes to extract dissolved salts from water under the influence of an electric field. This field drives the ions away from the products flow and continuously regenerates the resin beads, avoiding the need for chemical regeneration. The combination of reverse osmosis and electrodeionization is claimed to be the safest and most reliable way to produce purified water. 

Isolate. A relatively pure chemical produced from natural raw materials by physical means, eg, distillation, extraction, crystallization, etc, and therefore natural or by chemical means, ie, via hydrolysis, bisulfite addition products, and regeneration, etc, and therefore artificial by 1993 U.S. labeling regulations. 

The chemical yield of hydrogen peroxide and the anthraquinone per process cycle is very high, but other secondary reactions necessitate regeneration of the working solution and hydrogenation catalyst, and the removal of organic material from the extracted hydrogen peroxide. 

The Brio refining site is approximately 58 acres in size and is the location of a former chemical production, recovery, refinery, and regeneration facility. The site includes closed impoundments into which hazardous substances were disposed in bulk, storage tanks, and approximately 1,750 drums of hazardous substances. Remediation activities included the excavation and incineration of contaminated soil, installation of protective liners around selected pits, and the installation of a groundwater extraction system adjacent to a gully. 

A baseline potential pulse followed each current pulse in order to strip extracted ions from the membrane phase and, therefore, regenerated the membrane, making it ready for the next measurement pulse. This made sure that the potentials are sampled at discrete times within a pulse that correspond to a 6m that is reproducible from pulse to pulse. This made it possible to yield a reproducible sensor on the basis of a chemically irreversible reaction. It was shown that the duration of the stripping period has to be at least ten times longer than the current pulse [53], Moreover the value of the baseline (stripping) potential must be equal to the equilibrium open-circuit potential of the membrane electrode, as demonstrated in [52], This open-circuit potential can be measured prior to the experiment with respect to the reference electrode. 

When the resulting mixture of benzoylformic acid and (i )-mandelic acid was treated with a cell free extract of Streptomyces faecalis IFO 12964 in the presence of NADH,the keto acid can be effectively reduced to (i )-mandelic acid (Fig. 1). Fortunately the presence of A. bronchisepticus and its metabolite had no influence on the reduction of the keto acid. The regeneration of NADH was nicely achieved by coupling the reaction with reduction by formic acid with the aid of formate dehydrogenase. As a whole, the total conversion of racemic mandelic acid to the i -enantiomer proceeded with very high chemical and optical yields. The method is very simple and can be performed in a one-pot procedure [6]. 

After leaching, a concentration/pmification is done to get rid of other materials leached from the ore. This can be done by ion exchange or solvent extraction. In the ion exchange method, three steps are employed (a) the absorption of uranium from the leach liquor onto the resin, (b) the selective elution of uranium from the resin, and (c) the regeneration of the resin. Anion exchange is the preferred method of ion exchange with the relevant chemical reactions for acid leach being... 

Column. Although the advantage of the normal-phase column is the high resolution in the separation of all tocopherols and tocotrienols, the silica packing material in a normal-phase column is very reactive to strong polar chemicals. Any high-polarity compounds in the sample extract and mobile phase will diminish the column performance and shorten the column lifetime. It is very important to ensure that the sample extract is free of water and metal ions, and it is also advisable to regenerate the column routinely. 

However, the conditions are often far from those of industrial situations. In order to better simulate solvent degradation during the PUREX process, a test loop was created in the 1990s in a CEA laboratory (Fontenay-aux-Roses, France), with the EDIT loop (Extraction Desextraction Irradiation Traitement) (21, 22). The laboratory simulation of industrial conditions consisted of a succession of representative physical and chemical treatments after the irradiation of the solvent (i.e., alkali and acid treatments, distillation). Indeed, these treatments can modify the final solvent composition because of the elimination of some compounds or the occurrence of secondary reactions. A few years later, the MARCEL (Module Avance de Radiolyse dans les Cycles d Extraction Lavage) test loop was built at Marcoule to follow the regeneration efficiencies of degraded solvents involved in actinide separation processes (4, 5). 

Fedosev, D.A., Artemova, L.A., Romanovskaya, I.A., Dunaeva, M.Y., Vladimirova, M.V. 1996. Radiation-chemical behavior of plutonium in the 30% tributyl phosphate + -do-decane system under conditions of repeated y-irradiation and regeneration of extractant. Radiochemistry 38(1) 78-80. (Translated from Radiokhimiya 38(1) 84—87.)... 

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