Tributyl phosphate concentration

The nergistic effect was found to be dependent on the diluent. It is pronoimced with a mixed dodecane/xylene diluent, and is weak with mixed heptane/xylene, hex-ane/xylene, and pure xylene diluents. The organic phase was found to eontain simultaneously two or three synergistie complexes, with the compositions (A+)(Ln(N03)4-2B ), (A )(Ln(N03)4 3B ), and (A )2(ln(N03)5-B ), where Ln is a lanthanide (HI), A is a trioctylmethylammonium cation and B is a tributyl phosphate molecule. The synergistie complex stability was found to decrease with inerease in atomie number. Increasing the tributyl phosphate concentration gradually suppressed the separation factors for Pr-Nd and Eu-Gd pairs. 

The uranium(iv)-cerium(iv) reaction has been investigated in tributyl phosphate-chloroform solutions. The reaction is second-order overall and in 20—30% BU3PO4 the rate constant is about two orders of magnitude lower than for the corresponding aqueous reaction at the same temperature. As in the aqueous system, the rate is inversely dependent on hydrogen-ion concentration. The activation energy is also similar to that in water and is independent of tributyl phosphate concentration and pH. 

In TBP extraction, the yeUowcake is dissolved ia nitric acid and extracted with tributyl phosphate ia a kerosene or hexane diluent. The uranyl ion forms the mixed complex U02(N02)2(TBP)2 which is extracted iato the diluent. The purified uranium is then back-extracted iato nitric acid or water, and concentrated. The uranyl nitrate solution is evaporated to uranyl nitrate hexahydrate [13520-83-7], U02(N02)2 6H20. The uranyl nitrate hexahydrate is dehydrated and denitrated duting a pyrolysis step to form uranium trioxide [1344-58-7], UO, as shown ia equation 10. The pyrolysis is most often carried out ia either a batch reactor (Fig. 2) or a fluidized-bed denitrator (Fig. 3). The UO is reduced with hydrogen to uranium dioxide [1344-57-6], UO2 (eq. 11), and converted to uranium tetrafluoride [10049-14-6], UF, with HF at elevated temperatures (eq. 12). The UF can be either reduced to uranium metal or fluotinated to uranium hexafluoride [7783-81-5], UF, for isotope enrichment. The chemistry and operating conditions of the TBP refining process, and conversion to UO, UO2, and ultimately UF have been discussed ia detail (40). 

In practice, uranium ore concentrates are first purified by solvent extraction with tributyl phosphate in kerosene to give uranyl nitrate hexahydrate. The purified uranyl nitrate is then decomposed thermally to UO (eq. 10), which is reduced with H2 to UO2 (eq. 11), which in turn is converted to UF by high temperature hydrofluorination (eq. 12). The UF is then converted to uranium metal with Mg (eq. 19). 

Gd gestational day (Gl) = gastric intubation (GO) = gavage in oil Hemato - hematological incr. = increased IPTPP = isopropyl triphenyl phosphate LD = lethal dose, 50% kill LOAEL = lowest-observed-adverse-effect level M = male MCV = mean corpuscular volume MCHC = mean corpuscular hemoglobin concentration mo = month(s) Musc/skel = musculoskeletal NOAEL = no-observed-adverse-effect level NS = not specified NTE = neurotoxic esterase RBC red blood cell Resp = respiratory TBEP = tributoxyethyl phosphate TBP = tributyl phosphate TMP = trimethyl phosphate TNBP = tri-n-butyl phosphate TOP = trioctyl phosphate wk = week(s) x = times yr = year(s). 

A component of Skydrol 500B and Skydrol LD (tributyl phosphate) was detected in the air at the CP air test facility at Vancouver International Airport at a concentration of 0.04-0.3 mg/m3 (Labour-Canada 1990), indicating that organophosphate ester hydraulic fluids maybe released during aircraft maintenance operations on equipment using organophosphate ester hydraulic fluids. 

Organophosphate ester components of hydraulic fluids such as triphenyl phosphate, nonylphenyl diphenyl phosphate, and cumylphenyl phosphate also have been detected in fish concentrations of 0.1-0.9 pg/g of fish tissue were detected principally near manufacturing facilities, while fish caught in other areas generally had concentrations below the detection limit (0.1 pg/g) (Mayer et al. 1981). In a market basket survey, tributyl phosphate was found to be present in 2% of the foods analyzed between April 1982 and April 1984 (Gunderson 1988). Intakes of tributylphosphate were estimated to be a maximum of 38.9 ng/kg body weight/day for 6- to 11-month-old children. 

The thermal decomposition of liquid tributyl phosphate at 178-240 °C may be followed by the rate of formation of dibutylphosphoric acid. Below 3% decomposition the reaction is first-order. At higher acid concentrations acid catalysis is observed. The main reaction seems to be dealkylation... 

It is interesting to observe that alkylammonium salts, alkylarylsnlfonic acids, hydroxyoximes, aUcylphosphoric acids, and alkylhydroxamic acids, as well as nentral extractants such as crown ethers and tributyl phosphate, all form water-organic interfaces saturated with extractant molecules when their bulk organic concentration is larger than 10" M. 

Finely-ground monazite is treated with a 45% NaOH solution and heated at 138°C to open the ore. This converts thorium, uranium, and the rare earths to their water-insoluble oxides. The insoluble residues are filtered, dissolved in 37% HCl, and heated at 80°C. The oxides are converted into their soluble chlorides. The pH of the solution is adjusted to 5.8 with NaOH. Thorium and uranium are precipitated along with small quantities of rare earths. The precipitate is washed and dissolved in concentrated nitric acid. Thorium and uranium are separated from the rare earths by solvent extraction using an aqueous solution of tributyl phosphate. The two metals are separated from the organic phase by fractional crystallization or reduction. 

Fig. 6.39 Response of WF-FET with poly(phosphazene/benzoquionone) gate to low and high concentration of tributyl phosphate (adapted from Li et al., 1996)...

The volume leaders among fire retardants with 35 million pounds were the three phosphate plasticizers for PVC tricresyl phosphate, cresyl diphenyl phosphate and triphenyl phosphate. The remaining 6 million pounds were made up of octyl diphenyl phosphate, tributyl phosphate, tri(dibromopropyl) phosphate, tri(dichloropropyl) phosphate and tri-(chloroethyl) phosphate. Polymeric phosphorus and phosphorus halogen-containing additives are used in concentrations of 3-25 p.p.h. in polyesters, flexible and rigid polyurethane foam, and phenolics. 

Advantage may be taken of these conditions by use of solvent extraction techniques. It is known (25-30) that Am extraction with TBP ( tributyl phosphate) or DBBP (dibutyl butyl phos-phonate) is enhanced by high nitrate salt concentrations in the aqueous phase, particularly at HN03 concentrations below 1.0 N. 

Chemex [Chemical exchange] A process for separating uranium isotopes, based on the equilibrium between U3+ and U4+ in aqueous solution. U-238 concentrates in the LP+ state and U-235 in the U4+. Uranium in the two valence states is separated by solvent extraction into tributyl phosphate. Developed and piloted in France but not commercialized. 

The general chemistry of Ac3 in both solid compounds and solution, where known, is very similar to that of lanthanum, as would be expected from the similarity in position in the Periodic Table and in radii (Ac3, 1.10 La3, 1.06 A) together with the noble gas structure of the ion. Thus actinium is a true member of Group 3, the only difference from lanthanum being in the expected increased basicity. The increased basic character is shown by the stronger absorption of the hydrated ion on cation-exchange resins, the poorer extraction of the ion from concentrated nitric acid solutions by tributyl phosphate, and the hydrolysis of the trihalides with water vapor at 1000°C to the oxohalides AcOX the lanthanum halides are hydrolyzed to oxide by water vapor at 1000°C. 

The tributyl phosphate extraction method, where control of the concentration of nitric acid from 6 to 16 M allows control of the transfer of various actinide ions into kerosene containing 30% (C O O. 

Carbonate Complexes. Of the many ligands which are known to complex plutonium, only those of primary environmental concern, that is, carbonate, sulfate, fluoride, chloride, nitrate, phosphate, citrate, tributyl phosphate (TBP), and ethylenediaminetet-raacetic acid (EDTA), will be discussed. Of these, none is more important in natural systems than carbonate, but data on its reactions with plutonium are meager, primarily because of competitive hydrolysis at the low acidities that must be used. No stability constants have been published on the carbonate complexes of plutonium(III) and plutonyl(V), and the data for the plutoni-um(IV) species are not credible. Results from studies on the solubility of plutonium(IV) oxalate in K2CO3 solutions of various concentrations have been interpreted to indicate the existence of complexes as high as Pu(C03) , a species that is most unlikely from both electrostatic and steric considerations. From the influence of K2CO3 concentration on the solubility of PuCOH) at an ionic strength of 10 M, the stability constant of the complex Pu(C03) was calculated (10) to be 9.1 X 10 at 20°. This value... 

Solvent extraction is widely used for separation of radionuclides, because this technique is simple, fast and applicable in the range of low concentrations. Addition of a carrier is not required. Some examples of separation of radionuclides by solvent extraction are given in Table 12,8, As already mentioned in section 11,6, solvent extraction plays an important role in reprocessing. Tributyl phosphate (TBP), methyl isobutyl ketone (Hexon) and trilaurylamine (TLA) are preferred complexing agents for separation and purification of U and Pu,... 

Supported liquid membranes, consisting of an organic solution of -octyl(phenyl)-A,iV-diisobutylcarbamoylmethylpho-sphine oxide (CMPO) and tributyl-phosphate (TBP) in decalin, were capable of selective separation and concentration of actinide and lanthanide ions from aqueous nitrate feed solutions and from synthetic nuclear wastes where the strip solution is a mixture of formic acid (FA) and hydroxylammonium formate (HAF) [106,107]. TBP is added to CMPO to improve its solubility in aliphatic diluents. Although low concentration of nitric acid was initially used as the strippant solution, a gradual... 

Nowak [62] examined the influence of radiation on the system dodecane -30% TBP tributyl phosphate--nitric acid used as extractants of burned up nuclear fuel and found that nitro compounds were formed even at low concentrations of nitric acid. Nitroso and carbonyl compounds were also formed. 

The Acid-Thorex process has been used in recent years to recover 233U from neutron irradiated thoria targets. (] M This process uses n-tributyl-phosphate (TBP) in normal paraffin hydrocarbon (NPH) as the extractant and the relative uranium and thorium solubilities in each phase are adjusted by control of the nitric acid concentration. The Acid-Thorex process is the primary candidate for use in proposed aqueous thorium fuel cycles. In this process, uranium is separated from thorium through exploitation of the difference in equilibrium distributions since no usable valence change is available to aid in this separation. 

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