Preparation and biodistribution of 131I-labeled graphene quantum dots

Uranium sorption from commercial phosphoric acid was carried out onto kaolinite and metakaolinite. The different factors affecting uranium adsorption have been investigated. The obtained results show that, the sorption process is applicable for the high strength phosphoric acid, 40% P₂O₅, and diluted phosphoric acid, 20% P₂O₅, but it preferred to the diluted phosphoric acid. The kinetic models applied to the sorption rate data were evaluated for Lagergren first order and the pseudo second order models. From the results, the uranium sorption from commercial phosphoric acid, 40% P₂O₅, onto kaolinite and metakaolinite was found to occur through physical sorption process.     

Effect of Hexamethyi Phosphoric Acid Triamide on the Polymerization of Epichlorohydrin-Methyl Methacryiate Initiated with Alkylaluminum

Abstract

The effect of hexamethyi phosphoric acid triamide on the rate of polymerization of AlEt₃-initiated polymerization of epichloro-hydrin and methyl methacryiate was examined. Benzene was used as solvent and the experiments covered AlEt₃ /hexamethyi phosphoric acid triamide ratios from 1:0 to 1:2. Rate of polymerization increased to a maximum at AlEt₃/ hexamethyi phosphoric acid triamide ratio of 1:0.2 and then decreased.

The reaction of hexamethyi phosphoric acid triamide with AlEt, appears to modify the catalytic nature and copolymeriza-tion of epichlorohydrin with methyl methacryiate as demonstrated by enhanced methyl methacryiate reactivity in the presence of hexamethyi phosphoric acid triamide.     

Polymerization of Acrylamide and Copolymerization with Acrylonitrile with AIEt3-Hexamethyl Phosphoric Acid Triamide Complex

The polymerization of acrylamide and its copolymerization with acrylonitrile were investigated with AIEt₃ and AIET₃-hexamethyl phosphoric acid triamide. AIEt₃ initiates the polymerization of acrylamide. The addition of hexamethyl phosphoric acid triamide greatly influences the yields of methanol-insoluble polymer, η_sp/c, and the structure of polymer. Vinyl polymerization is dominant with AIET₃ in the presence of hexamethyl phosphoric acid triamide. On copolymerization of acrylamide with acrylonitrile, the acrylonitrile content in the copolymer increased with the addition of hexamethyl phosphoric acid triamide on AIEt₃.     

Evolution of gaseous products from biomass pyrolysis in the presence of phosphoric acid

Slow pyrolysis experiments of China fir (Cunninghamia lanceolata) wood were performed in a vertical tubular furnace at various heating rates. The raw material was pretreated by impregnation with phosphoric acid solutions of various concentrations for given times. The evolution of the gaseous products CO, CO₂, H₂ and CH₄ was analyzed online by using gas spectrometry to investigate the effect of phosphoric acid on the pyrolytic gaseous products of biomass. The addition of phosphoric acid was shown to significantly reduce the pyrolysis temperature necessary for the production of CO, CO₂ and H₂ gases, and the pyrolysis variables exerted an influence on the amount of the gases released. Moreover, phosphoric acid appreciably depressed the CO, CO₂ and CH₄ production, and promoted H₂, especially when a higher heating rate was employed. This suggested that phosphoric acid catalyzed both the primary thermal decomposition of biopolymers and the secondary reactions that took place among the pyrolytic vapor products.     

Effect of oxidation-reduction on the extraction of uranium from wet phosphoric acid by DEHPA/TOPO

Uranium is recovered from wet phosphoric acid by DEHPA/TOPO in kerosene. Uranium is present in wet phosphoric acid in the tetravalent and hexavalent states but DEHPA/TOPO extracts uranium in the hexavalent state only. The ratio of U⁴⁺/U⁶⁺ depends on several factors such as the origin of the phosphate rock, the method of preparation of phosphoric acid and the presence of other impurities. Therefore it is important to oxidize the wet acid to convert all uranium to U⁶⁺ before extraction. Uranium is stripped from the solvent by a reverse process where a concentrated phosphoric acid is used under reducing conditions. This paper studies the oxidation of wet phosphoric acid from Homs plant/Syria by H₂O₂ oxidant and the effect of oxidation on extraction coefficientK. It also studies the reduction by iron and its effect on back extraction of uranium from the solvent to phosphoric acid.     

Determination of uranium in phosphoric acid by XRF using lacunary polytungstophosphate salt (K10P2W17O61)

Uranium in phosphoric acid was determined by the calibration curve method. The prepared samples, resulting from the adsorption of uranium from phosphoric acid solution on lacunary polytungstophosphate salt (K₁₀P₂W₁₇O₆₁) are thin and proved to be suitable for XRF analysis.     

Determination of uranium in wet phosphoric acid by extraction with octylphenylphosphoric acid

A method for quantitative determination of uranium in phosphoric acid and wet phosphoric acid has been developed. After reduction with Fe, uranium(IV) is extracted with a kerosene solution of octylphenylphosphoric acid. The uranium was stripped with 10M H₃PO₄, containing H₂O₂, and then determined spectrophotometrically with Arsenazo III and by direct uranium(IV)-phosphoric acid solution measurements.     

SILICA PHOSPHORIC ACID/NaNO2 AS A NOVEL HETEROGENEOUS SYSTEM FOR THE COUPLING OF THIOLS TO THEIR CORRESPONDING DISULFIDES

Silica phosphoric acid was prepared via reaction of silica chloride (I) and phosphoric acid. Thiols can be readily converted to their corresponding thionitrites with a combination of silica phosphoric acid (II), wet SiO ₂ , and sodium nitrite in dichloromethane at room temperature. Disulfides result from the homolytic cleavage of the sulfur–nitrogen bond of the unstable thionitrite and subsequent coupling of the resultant thiyl radicals.     

A new anhydrous proton conducting material based on phosphoric acid doped polyimide

A new anhydrous proton conducting material based on polyimide and phosphoric acid composite was prepared. The interaction between polyimide (PI) and phosphoric acid was investigated by FTIR. The results show that phosphoric acid interacts with polyimides mainly by hydrogen bonds rather than by protonation of PI at room temperature. Environmental scanning electron microscopy (ESEM) was employed to study the surface morphology of the membranes. The results show that the surface of PI-xH₃PO₄ membranes is very compact and homogeneous. Proton conductivity and methanol permeability of PI doped with phosphoric acid (PI-xH₃PO₄) were also studied. Proton conductivity of PI-xH₃PO₄ membranes increases with increasing concentration of phosphoric acid. Hydrogen bond seems to play an important role in the proton conductivity of this system. Effects of osmotic on the direct diffusion process of methanol in the membranes can be negligible due to the absence of micro-pore structure as already shown in ESEM results. Effects of methanol concentration and temperature on the methanol permeability of PI-xH₃PO₄ membranes were also discussed. Methanol permeability in PI-xH₃PO₄ membranes decreases with increasing methanol concentration, and increases with increasing temperature.     

手性磷酸在不对称反应中的应用

手性磷酸催化剂因其在不对称催化反应中表现出的高效、高对映选择性而受到人们越来越多的关注.含1,1'-联二萘酚(BINOL)骨架的手性磷酸类催化剂已被广泛用于亚胺的不对称氢转移、Friedel-Crafts反应和Mannich反应等许多重要的有机合成反应.手性磷酸具有同时提供质子和接受质子的双功能作用,因此可以同时活化两个反应底物.含BINOL骨架的手性磷酸可以通过改变BINOL骨架3,3'-位上的取代基调控空间位阻和手性磷酸的酸性,因此可以调节反应的对映选择性.为了合理地设计新的手性磷酸催化剂,扩大其应用范围,最近人们对手性磷酸不对称催化反应机理进行了初步的理论计算研究并取得了显著进展.综述了手性磷酸在不对称反应中的部分研究工作,尤其是理论研究领域的最新成果.     

Synthese von N-Di(alk-, ar-)oxyphosphoryl-tri(alk-, ar-)-oxyphosphazenen, (RO)2P(O)?NP(OR)3, durch P?N-Bindungsknüpfung

Synthesis of N-Di(alk-, ar-)oxyphosphoryl-tri(alk-, ar-)oxyphosphazenes, (RO)₂P(O)? N?P(OR)₃, by P? N-Bond Formation The title compounds can be prepared from di- and triesters of phosphorous acid, sodium azide, and carbon tetrachloride in a single step procedure and in high yields. Due to the combination of the Atherton-Todd and the Staudinger reaction toxic phosphoric acid ester azides are formed only in situ and their concentration is kept very small. As by-products trichloromethane phosphonic acid esters, (RO)₂P(O)CCl₃, esters of phosphoric acid and condensed phosphoric acids as well as N-alkylimidodiphosphoric acid esters, [(RO)₂P(O)]₂NR, are formed. Their formation can be avoided or reduced by choosing suitable reaction conditions. The mechanism of the reaction is discussed.     

Free Phosphoric Acid of Diatomite-Phosphate Solid Acid and its Catalytic Performance for Propylene Oligomerization

Free phosphoric acid in the diatomite-phosphate solid acid catalysts was characterized by means of ion chromatography (IC), Hammett pH indicators and chemical titration. The results show that the free phosphoric acid is composed of 535 wt.% H₃PO₄, 17 wt.% H₄P₂O₇ and < 1 wt.% polyphosphoric acid, and its composition determines the acid strength distribution of the catalyst. When the total amount of free phosphoric acid containing >3 wt.% H₄P₂O₇ is within 9 26 wt.% (in P₂O₅), the catalyst shows higher catalytic activity for propylene oligomerization with propylene conversion >75wt.%. Besides, free phosphoric acid has an important effect on the catalytic selectivity. The relationship between them is discussed.     

A Study of Viscosity in the Extraction System Constituted by Tributyl Phosphate and Phosphoric Acid

Data on the kinematic viscosity of phosphoric acid solutions in technical-grade tributyl phosphate and in an industrial extract from a technological purification system based on tributyl phosphate, which contain 0–18% phosphoric acid in terms of P₂O₅, at 10–70°C are presented.     

The influence of cations in phosphoric acid on the extraction of uranium

Commercial phosphoric acid produced by the wet method is not a purecompound. It contains many contaminants. This paper studied the effect ofcertain cations in the commercial phosphoric acid produced by SIAPE wet methodin Homs General Fertilizer Company on the distribution coefficient (K d )ofuranium . The effect of Fe ₃+ , Fe₂+ , Mg₂+, Ca ₂+ , Al ₃+ and V ₅+ on uranium extractionby D2EHPA/TOPO was investigated according to the factorial design method.The results obtained showed that Al ₃+ and Ca ₂+ hada marked beneficial effect on uranium extraction while Mg ₂+ ,Fe ₃+ and V ₅+ had a negligible effect. An increasein Fe ₂+ led to a decrease in the extraction of UO ₃2+ from phosphoric acid.     

Solubility and physic-chemical properties of NaH2PO4 in phosphoric acid,sodium chloride and their mixture solutions at T = (298.15 and 313.15) K

In this study, solubility and physic-chemical properties of sodium dihydrogen phosphate in sodium chloride, phosphoric acid and their mixture solutions at T = (298.15 and 313.15) K have been investigated by using isothermal dissolution method. In the three systems, the solubility of NaH₂PO₄ always increases with the temperature increasing and decreases with molar concentration of phosphoric acid (sodium chloride) increasing because of the same ion effect. Solubility data of sodium dihydrogen phosphate in the mixed solution of sodium chloride and phosphoric acid is basically required for designing and optimizing the solvent extraction process in the industrial production.     

Direct uranium extraction from dihydrate and hemi-dihydrate wet process phosphoric acids by liquid emulsion membrane

A new liquid emulsion membrane (LEM) process for uranium extraction from either dihydrate 28-30% P₂O₅ (DH) or hemi-dihydrate 42-45% P₂O₅ (HDH) wet process phosphoric acid is proposed. In this process, the organic component of the LEM is composed of a synergistic mixture of 0.1M di-2-ethyl hexyl phosphoric acid (DEHPA) and 0.025M trioctyl phosphine oxide (TOPO) with 4% Span 80. The internal or the strip acid phase is composed of 0.5M citric acid. The prepared LEM was proved to be stable in 42-45% P₂O₅ acid concentration range and can, therefore, be applied to the phosphoric acid produced by the hemi-dihydrate process. After breakdown of the loaded emulsion, the uranyl citrate in the internal strip phase is separated by adding methanol followed by its calcination to the orange oxide. Most of the reagents used are recycled. The proposed process is characterized by simplicity, practically closed operation cycle in addition to lower capital and operating costs.     

Kinetic studies on the extraction of uranium(VI) from phosphoric acid medium by bulk liquid membrane containing di-2-ethylhexyl phosphoric acid

To go through the first stage of industrial solvent extraction process in order to recover uranium from phosphate rocks by liquid membrane techniques, as a simple model, the kinetics of facilitated transport of uranium(VI) from a dilute phosphoric acid medium into more concentrated phosphoric acid media as a receiving phase through a bulk liquid membrane containing di-2-ethylhexyl phosphoric acid as a carrier was studied. The influence of phosphoric acid concentration in the source and receiving phases, carrier concentration, type of solvent, stirring speed and temperature were investigated. The kinetic parameters (k _e, k _s, t _max, J _max) were calculated for the interface reactions assuming two consecutive, irreversible first-order reactions. The activation energy values were calculated as 29.40 and 19.51 kJ mol^?1 for extraction and stripping, respectively. The values of calculated activation energy indicated that both the extraction and stripping processes were controlled by mixed regime (both kinetic and diffusion). In addition, the influence of adding trioctyl-phosphine oxide into the membrane phase as a synergic agent on the transport kinetics was determined.     

Investigation of Uranium(VI) Extraction Mechanisms from Phosphoric and Sulfuric Media by 31P-NMR

Uranium extraction using DEHCNPB (butyl-1-[N,N-bis(2-ethylhexyl)carbamoyl]nonyl phosphonic acid, a bifunctional cationic extractant) has been studied to better understand mechanism differences depending on the original acidic solution (phosphoric or sulfuric). Solvent extraction batch experiments were carried out and the organic phases were probed using ³¹P-NMR. This technique enabled to demonstrate that phosphoric acid is poorly extracted by DEHCNPB ([H₃PO₄]_org < 2mM), using direct quantification in the organic phase by ³¹P-NMR spectra integration. Moreover, in the presence of uranium in the initial phosphoric acid solution, uranyl extraction by DEHCNPB competes with H₃PO₄ extraction.Average stoichiometries of U(VI)-DEHCNPB complexes in organic phases were also determined using slope analysis on uranium distribution data. Uranium seems to be extracted from a phosphoric medium by two extractant molecules, whereas more than three DEHCNPB on average would be necessary to extract uranium from a sulfuric medium. Thus, uranium is extracted according to different mechanisms depending on the nature of the initial solution.     

Determination of 210Po in Reagent Samples by Alpha-Ray Spectrometry Using Extraction Chromatographic Resin

The determination of ²¹⁰Po in phosphoric acid reagent by alpha-ray spectrometry using extraction chromatographic resin is presented. The decontamination factors of interference elements were measured. It was observed that HCl, HNO₃, ascorbic acid, thioacetamide and Cu were free from ²¹⁰Po but Pb contain small amounts of ²¹⁰Po. ²¹⁰Po in phosphoric acid samples was ranged from <8 to 2.4 Bq/l. The detection limit of ²¹⁰Po in 50 ml of phosphoric acid is 8 mBq/l with a counting time of 1 day undercounting efficiency of 30%.     

Dissolution of sintered thorium dioxide in phosphoric acid using autoclave and microwave methods with detection by gamma spectrometry

A quantitative and fast method of dissolution of refractory thoria (ThO₂) was developed for the determination of thorium (Th) in a given sample. The dissolution of sintered ThO₂ powder, microspheres and pellets using 88% phosphoric acid was investigated. The conditions of quantitative dissolution of ThO₂ microspheres were optimized by conventional heating in autoclave and also by microwave heating. 100 mg of sintered ThO₂ microspheres were dissolved in 8 g of phosphoric acid in an autoclave, and heating at 170 °C for 3 h, in comparison to 5 g of phosphoric acid by microwave heating (375 W) at 220 °C for 1 h. Dissolution studies on the powder form of sintered ThO₂ were also performed. 1 g of sintered ThO₂ powder could be dissolved in 6.5 g of phosphoric acid in autoclave heating at 170 °C for 1 h. Strong complexing of (PO₄)³⁻ with Th⁴⁺ may be the influencing factor for quantitative dissolution of ThO₂.