Nitrate/fluoride process

A continuous nitrate/fluoride process has been proposed to take advantage of the ready solubility of columbite ore in a mixture of nitric and hydrofluoric acids, and thus allow the feed solution to be prepared in a cheap and simple manner. The feed contains 45 g/1. of niobium, about 25 g/1. of tantalum and is 8N in hydrofluoric acid and 3N in nitric acid. It is extracted in six stages with three volumes of solvent, together with an additional stage for acid equilibration . A half volume aqueous strip solution is also 8N in hydrofluoric acid and 3N in nitric acid. About 99 per cent of the niobium is extracted into the solvent and is then backwashed in a second extractor with three volumes of 0-5N hydrofluoric acid. The solvent finally passes to a single-stage backwash extractor for removal of tantalum by sodium carbonate solution. 

The cr-complexes (iv) are thus the intermediates corresponding to the substitution process of hydrogen exchange. Those for some other substitutions have also been isolated in particular, benzylidyne trifluoride reacts with nitryl fluoride and boron trifluoride at — ioo°C to give a yellow complex. Above — 50 °C the latter decomposes to hydrogen fluoride, boron trifluoride, and an almost quantitative yield of tn-nitrobenzylidyne trifluoride. The latter is the normal product of nitrating benzylidyne trifluoride, and the complex is formulated as... 

The plutonium extracted by the Purex process usually has been in the form of a concentrated nitrate solution or symp, which must be converted to anhydrous PuF [13842-83-6] or PuF, which are charge materials for metal production. The nitrate solution is sufficientiy pure for the processing to be conducted in gloveboxes without P- or y-shielding (130). The Pu is first precipitated as plutonium(IV) peroxide [12412-68-9], plutonium(Ill) oxalate [56609-10-0], plutonium(IV) oxalate [13278-81-4], or plutonium(Ill) fluoride. These precipitates are converted to anhydrous PuF or PuF. The precipitation process used depends on numerous factors, eg, derived purity of product, safety considerations, ease of recovering wastes, and required process equipment. The peroxide precipitation yields the purest product and generally is the preferred route (131). The peroxide precipitate is converted to PuF by HF—O2 gas or to PuF by HF—H2 gas (31,132). 

A hydrochloric acid process for the manufacture of anatase has been proposed but has not been developed. Other routes include fluoride, bromide, nitrate, sulfide, and chloroacetate processes (1). None of these, however, has been used successfully on a commercial scale. 

Acid treatments The principal acid processes were developed in the USA under the name Alodine, and are marketed in the UK as Alocrom and under other names. The original solutions were based on acid solutions containing phosphate, chromate and fluoride ions. Immersion for up to 5 min in the cold or warm solution leads to the deposition of a greenish film containing the phosphates of chromium and aluminium, and possibly some hexavalent chromate. The more recent Alocrom 1 200 process uses an acid solution containing chromate, fluoride and nitrate. Room-temperature immersion for 15 s to 3 min deposits golden-brown coatings which contain chromate as a major constituent. 

Disproportionation of Pu(IV). There are several needs associated witn the occurrence, detection, and mitigation of the disproportionation of Pu(IV) in applied plutonium recovery/ purification procedures. First, there is a great need for much more detailed information concerning the effect of typical process conditions [e.g., temperature, concentration of plutonium, hydrogen ion, nitrate ion, nitrite ion, fluoride ion, other metal ions (e.g., A13+, Fe3+, etc.), etc.] on the occurrence and extent of the reaction ... 

Precipitation Processes. Plutonium peroxide precipitation is used at Rocky Flats to convert the purified plutonium nitrate solution to a solid (14) the plutonium peroxide is then calcined to Pu02 and sent to the reduction step. The chemistry of the plutonium peroxide precipitation process is being studied, as well as alternative precipitation processes such as oxalate, carbonate, fluoride, and thermal denitration. The latter method shows the most promise for cost and waste reduction. 

Trifluoromethyl)benzene (benzotrifluoride, 15) was the first organic fluoride to incorporate a trifluoromethyl group. By a standard nitration process, it formed l-nitro-3-(trifluoromethyl)-benzene (16) which was reduced to the 1-amino derivative, 17. This we a-directive influence on electrophilic aromatic substitution contrasted with that for fluorobenzene, which gave 4-and 2-nitro products. 

This AQUATECH acid recycle system is the first of its kind in the world. It was designed to recycle 1.6 million gallons of waste acid a year, recovering 90% of the total fluoride and nitrates resources. The waste volume is reduced by 90% to the resultant solid metal hydroxide cake which is then recycled to the furnace. Over the past two years of operation, the system successfully reduced the acid waste hauled. Actual waste acid processed versus acid product regenerated are tracked in Figure 8. 

A method of separation which avoids the preparation of the double fluorides consists in fusing the mixed niobic and t an tali c acids with sodium carbonate and nitrate, the product is digested with warm water and a current of carbon dioxide is passed through the solution. It is claimed that only tantalic acid is precipitated.5 This process has, however, been the subject of adverse criticism.6 Partial separation of niobium from tantalum can be effected by warming the mixed, freshly precipitated, hydrated oxides with a mixture of hydrogen peroxide and hydrochloric acid the niobium dissolves readily, while the tantalum dissolves only sparingly.7... 

A. Mekonen, P. Kumar, A. Kumar, Integrated biological and physicochemical treatment process for nitrate and fluoride removal, Water Res. 35 (13) (2002) 3127-3136. 

To monitor tumor response to capecitabine therapy noninvasively, Zheng and co-workers, from the Indiana University School of Medicine, developed the synthesis of the fluorine- 18-labeled capecitabine as a potential radiotracer for positron emission tomography (PET) imaging of tumors.28 Cytosine (20) was nitrated at the C-5 position with nitric acid in concentrated sulfuric acid at 85°C, followed by neutralization to provide 5-nitrocytosine (27) in moderate yield. This nitro pyrimidine was then carried through the glycosylation and carbamate formation steps, as shown in the Scheme below, to provide the 6/s-protected 5-nitro cytidine 28 in 47% for the three-step process. Precursor 28 was then labeled by nucleophilic substitution with a complex of 18F-labeled potassium fluoride with cryptand Kryptofix 222 in DMSO at 150 °C to provide the fluorine-18-labe led adduct. This intermediate was not isolated, but semi-purified and deprotected with aqueous NaOH in methanol to provide [l8F]-capecitabine in 20-30% radiochemical yield for the 3-mg-scale process. The synthesis time for fluorine-18 labeled capecitabine (including HPLC purification) from end of bombardment to produce KI8F to the final formulation of [18F]-1 for in vivo studies was 60-70 min. 

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