Nitrate aqueous phase

Note that this reaction pathway will operate only in the nighttime, as during the daytime NO3 photolyzes rapidly. The NO3 radical formed during the nighttime also reacts with a series of organic compounds, producing organic nitrates. Aqueous-phase production of ni-... 

TBP and nitric acid also tend to form a complex with each other, but at sufftcientiy high uranyl nitrate concentrations the nitric acid is mainly displaced into the aqueous phase. 

Therefore the extent of extraction or back-extraction is governed by the concentration of X ia the aqueous phase, the distribution coefficients, and selectivities depending on the anion. In nitrate solutions, the distribution coefficient decreases as the atomic number of the REE increases, whereas ia thiocyanate solutions, the distribution coefficient roughly increases as the atomic number of the REE increases. The position of yttrium in the lanthanide series is not the same in nitrate and thiocyanate solutions, and this phenomenon has been used for high purity yttrium manufacture in the past. A combination of extraction by carboxyUc acids then by ammonium salts is also utilized for production of high purity yttrium. 

Manufacture and Processing. Mononitrotoluenes are produced by the nitration of toluene in a manner similar to that described for nitrobenzene. The presence of the methyl group on the aromatic ring faciUtates the nitration of toluene, as compared to that of benzene, and increases the ease of oxidation which results in undesirable by-products. Thus the nitration of toluene generally is carried out at lower temperatures than the nitration of benzene to minimize oxidative side reactions. Because toluene nitrates at a faster rate than benzene, the milder conditions also reduce the formation of dinitrotoluenes. Toluene is less soluble than benzene in the acid phase, thus vigorous agitation of the reaction mixture is necessary to maximize the interfacial area of the two phases and the mass transfer of the reactants. The rate of a typical industrial nitration can be modeled in terms of a fast reaction taking place in a zone in the aqueous phase adjacent to the interface where the reaction is diffusion controlled. 

The distribution of highly extractable solutes such as and Pu between the aqueous and organic phases is strongly dependent upon the nitrate anion concentration in the aqueous phase. This salting effect permits extraction or reextraction (stripping) of the solute by controlling the nitric acid concentration in the aqueous phase. The distribution coefficient, D, of the solute is expressed as... 

Uranium—Plutonium Partitioning". The uranium and plutonium are separated in the partitioning column by reducing the plutonium to a less extractable valence state. The plutonium nitrate transfers back to the aqueous phase and the uranium remains with the organic. 

The dimethyl ethers of hydroquiaones and 1,4-naphthalenediols can be oxidized with silver(II) oxide or ceric ammonium nitrate. Aqueous sodium hypochlorite under phase-transfer conditions has also produced efficient conversion of catechols and hydroquiaones to 1,2- and 1,4-benzoquiaones (116), eg, 4-/-butyl-l,2-ben2oquinone [1129-21-1] ia 92% yield. 

Ce(IV) extracts more readily iato organic solvents than do the trivalent Ln(III) ions providing a route to 99% and higher purity cerium compounds. Any Ce(III) content of mixed lanthanide aqueous systems can be oxidi2ed to Ce(IV) and the resultiag solutioa, eg, of nitrates, contacted with an organic extractant such as tributyl phosphate dissolved in kerosene. The Ce(IV) preferentially transfers into the organic phase. In a separate step the cerium can be recovered by reduction to Ce(III) followed by extraction back into the aqueous phase. Cerium is then precipitated and calcined to produce the oxide. 

Particular reactions can occur in either or both phases or near the interface. Nitration of aromatics with HNO3-H2SO4 occurs in the aqueous phase (Albright and Hanson, eds.. Industrial and Laboratoiy Nitration.s, ACS Symposium Series 22 [1975]). An industrial example of reaction in both phases is the oximation of cyclohexanone, a step in the manufacture of caprolactam for nylon (Rod, Proc. 4th Interna-tional/6th European Symposium on Chemical Reactions, Heidelberg, Pergamon, 1976, p. 275). The reaction between butene and isobutane... 

The selectivity issue has been related to multi-phase processing [31]. Nitrations include both organic and aqueous phases. Oxidation to phenol as one side reaction takes places in the organic phase, whereas all other reactions occur in the aqueous phase and are limited by organic solubility. For this reason, enhancing mass transfer by large specific interfaces is a key to affecting product selectivity. 

Liquid-liquid reactions occur between two or more liquid phases whereby a system consisting of an organic and an aqueous phase is applied most frequently. Usually reaction takes place in one phase only. Phase-transfer catalysts are sometimes used to make transfer of a reactant to the reacting phase easier. Among typical liquid-liquid reactions utilized in fine chemicals manufacture are nitrations with mixtures of nitric and sulphuric acid, conventional hydroxylations performed with hydrogen peroxide, esterifications, alkylations, brominations, and iodinations. 

To avoid excessive acid waste, lanthanide(III) triflates are used as recyclable catalysts for economic aromatic nitration. Among a range of lanthanide(III) triflates examined, the ytterbium salt is the most effective. A catalytic quantity (1-10 mol%) of ytterbium(III) triflate catalyzes the nitration of simple aromatics with excellent conversions using an equivalent of 69% nitric acid in refluxing 1,2-dichloromethane for 12 h. The only by-product of the reaction is water, and the catalyst can be recovered by simple evaporation of the separated aqueous phase and reused repeatedly for further nitration.12... 

The first experiments on chemoautotrophic theory were carried out by Stetter at the University of Regensburg. It was found that synergy in the FeS/H2S system determined the reductive effect, for example, in the conversion of nitrate to ammonia or of alkynes to alkenes. The conditions used corresponded to those present in hydrothermal systems aqueous phase, 373 K, almost neutral pH and anaerobic conditions (Blochl et al 1992). Two years later, the formation of an amide bond without the use of a condensation agent was successfully demonstrated in the same laboratory (Keller et al 1994). 

Test 1. Mix a quantity containing 40 mg of miconazole nitrate with 20 mL of a mixture of 1 volume of 1 M sulfuric acid and 4 volumes of methanol and shake with two 50 mL quantities of hexane, discarding the organic layers. Make the aqueous phase alkaline with 2 M ammonia and extract with two 40 mL quantities of chloroform. Combine the chloroform extracts, shake with 5 g of anhydrous sodium sulfate, filter, and dilute the filtrate to 100 mL with chloroform. Evaporate 50 mL to dryness and dissolve the residue in 50 mL of a mixture of 1 volume of 0.1 M hydrochloric acid and 9 volumes of methanol. The light absorption of the resulting solution, Appendix II B, in the range 230-350 nm exhibits maxima at 264, 272, and 282 nm. 

Into a three-necked flask (200 ml) equipped with a mechanical stirrer, an ion exchanger (0.3 g) and water (135 mL) were taken. The resulting mixture was allowed to stand overnight for swelling of the ion exchanger. Then, a lead nitrate solution (0.05 M, 15 ml) was added to the flask, and immediately the resulting solution was stirred at 400 rpm for the first 2 min, and then at 170 rpm. At pertinent intervals, an aliquot of the aqueous phase was sampled, and the concentration of Pb(II) in the sample was measured. From a decrease in the Pb(II) concentration in the aqueous phase, the uptake of Pb(II) at the sampled time was calculated. 

Many activations involve compounds which are used as pesticides. In the case of N-nitrosation, the precursors are secondary amines and nitrate. The former are common synthetic compounds and the latter is an anion found in nearly all solid and aqueous phases. The N-nitrosation of a secondary amine [R-NH-R ] occurs in the presence of nitrite formed microbiologically from nitrate. The product is an N-nitroso compound (i.e., a nitrosamine [RR -N-N=0]). The reason for concern with nitrosamines is their potency, at low concentrations, as carcinogens, teratogens, and mutagens. 

Goishi and Libby have investigated the extraction of pertechnetate from alkali solutions with pyridine. Later work showed that a better extraction is obtained using a mixture of sodium hydroxide and sodium carbonate as the aqueous phase. Since the uranyl carbonate complex is not extracted into pyridine, this system may be used for the separation of technetium from uranium. Distribution coefficients of fission products in pyridine are given in Table 4. Substituted pyridine such as 2,4-dimethylpyridine or 4-(5-nonyl)pyridine ) are useful for separating technetium from solutions containing appreciable amounts of aluminum nitrate. 

As already mentioned in section 2.1 pertechnetate may be efficiently extracted by pyridine from alkaline solutions Since pyridine derivates are less soluble in the aqueous phase than pyridine, they extract technetium more efficiently even from nitrate solutions. For example, the distribution coefficients of technetium in the extraction from a 2 M (NH )2COj solution with a high nitrate concentration by pyridine and 2-methylpyridine are 7.5 and 242, respectively . Higher distribution coefficients can be achieved by using 3-methyl- or 4-methyl-pyridines. The pyridine derivates are the most promising reagents for the extraction of technetium from nitrate solutions. 

In the aqueous phase we have included the U02(N03) complexes but excluded the U02(N03)2(TBP)2 complex, because the concentration of the last complex in the aqueous phase is negligible compared to the other two. In dilute solutions, the nitrate complex can be negleted compared to the free U02 concentration. In the latter case the U distribution equals... 

Using trace concentrations of Ce(III) and An(III) a log-log plot of Du against the nitrate ion activity, mj = [LiNOj], had a slope of approximately 3, Fig. 4.16b. From Eq. (4.64) this slope corresponds to the p-value of 3 when the aqueous phase is dominated hy the free metal ion, which is not an unreasonable assumption at low nitrate concentrations. 

Fig. 4.16 Distribution ratio of ions between the trUaurylmethyl ammonium nitrate (TLMA) in o-xylene and aqueous phases of varying LiNOj concentrations, (a) As a function of TLMANO3 concentration at 1-7 M, 2-5 M, 3-3 M LiNOj. (b) Extraction of Eu(in) and tree actinide(III) ions at 0.1 M TLMANO3 in o-xylene and varying aqueous salt concentrations. (From Ref. 29.)...

The extraction of the lanthanides from nitrate media with TBP [Eq. (11.20)] depends on several factors including pH, nitric acid concentration, ionic strength, and concentration of the elements in the aqueous phase. 

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