Extraction of tetravalent berkelium by tributyl phosphate from nitric acid solutions

Extraction of Bk(IV), Ce(IV), Pu(IV) and Zr by tributyl phosphate from 2M to 16M nitric acid solutions has been studied. Using the data on the effect of the extractant, nitric acid and nitrate ion concentrations on the distribution coefficients of Bk(IV) and Ce(IV), the mechanism of Bk(IV) extraction by tributyl phosphate from nitric acid solutions is considered.     

Desorption of nitric acid from boehmite and gibbsite

Solid-state Fourier transform infrared spectroscopy (FTIR), evolved gas analysis-FTIR (EGA-FTIR), thermal gravimetric analysis (TGA), and differential scanning calorimetry (DSC) have been used to investigate the desorption of nitric acid from boehmite and from gibbsite. Samples containing between 3 and 36% of adsorbed nitric acid by mass were prepared by placing the mineral in a 70% nitric acid solution or by the adsorption of nitric acid vapors in humid air. FTIR established that water-solvated nitrate was the main species adsorbed on the surface of either mineral under these conditions. The water-solvated nitrate vaporized as nitric acid at approximately 400 K with an enthalpy of desorption of approximately 50 kJ/mol for both surfaces. A second nitric acid desorption occurred at approximately 450 K and had an enthalpy of desorption of 85 kJ/mol (95 kJ/mol) for boehmite (gibbsite). This was assigned as desorption of partially solvated aluminum hydroxylated nitrate. Monodentate and bridging nitrate were also observed on the boehmite. These species desorbed at approximately 725 K as NO2 and O2 with an enthalpy of reaction of approximately 55 kJ/mol of NO2 desorbed.     

土壤中铅的分析方法比对

对不同的样品消解方法及电感耦合等离子体质谱、电感耦合等离子体原子发射光谱、石墨炉原子吸收光谱法测定土壤中铅的测定结果进行比对。采用电热板、微波及水浴3种加热方式,选择硝酸、氢氟酸、双氧水、王水、高氯酸、盐酸的不同组合进行土壤样品消解,通过分析测定值的精密度和准确度,考察消解体系对电感耦合等离子体质谱、电感耦合等离子体发射光谱、石墨炉原子吸收光谱法测定结果的影响。结果表明采用电感耦合等离子体质谱法测定土壤中的铅,最适宜的消解体系是硝酸-氢氟酸-高氯酸(微波加热),采用电感耦合等离子体原子发射光谱法测定最适宜的消解体系是硝酸(电热板加热),采用石墨炉原子吸收光谱法测定最适宜的消解体系是硝酸-盐酸-高氯酸(微波加热)。电感耦合等离子体质谱法的精密度和准确度优于另外两种方法。     

单斜相WO_3的水热合成及其光催化性能的研究

利用水热合成法,以钨酸钠为钨源,硝酸为酸源,柠檬酸与酒石酸为辅助剂,制备了单斜相且形貌规整的WO_3。对WO_3样品进行了X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)及紫外可见漫反射(UV-vis-DR)分析,测试了样品的BET比表面积,考察了硝酸与钨原子物质的量比,柠檬酸、酒石酸与钨原子物质的量比对样品晶相与形貌的影响。结果表明,大量硝酸及羟基酸的加入都有利于WO_3单斜相的形成,当硝酸与钨原子的物质的量比为2.8∶1,羟基酸与钨原子的物质的量比为0.8∶1时,能够制得单斜相、形貌规整的WO_3样品。将WO_3与p型半导体物质CuCrO_2复合得到CuCrO_2-WO_3复合催化剂用于光催化分解水产氢的实验,高结晶度的单斜相WO_3具有较好的光催化性能。     

Dynamic adsorption of uranium(VI) and zirconium(IV) on silica gel

Adsorption of uranium(VI) and zirconium(IV) from aqueous nitric acid solution on silica gel has been investigated under dynamic conditions. The influence of temperature, nitric acid concentration (pH), and solution flow rates was studied. If the nitric acid concentration in the solution is higher than 0.05 mol/l, then it is possible to achieve separation of uranium(VI) and zirconium(IV) by passing the solution through a column filled with silicagel.     

Kinetic studies on the solvent extraction of uranium (IV), thorium (IV) and uranium (VI) from nitric acid solutions with tributyl phosphate

The kinetics of solvent extraction of U (IV), Th (IV) and U (VI) from nitric acid solution with tributyl phosphate (TBP) in kerosene and cyclohexane have been studied using the single drop technique. The effects of concentrations of U (IV), Th (IV), U (VI), nitric acid, nitrate, TBP and temperature on the extraction rates of U (IV), Th (IV) and U (VI) have been examined. The mechanisms for the three extraction processes are discussed.     

Extraction of uranyl(VI) ion with N,N-diethyloctadecanamide from nitric acid solution

The extraction of U(VI) with newly synthesized alkylamide, N,N-diethyloctadecanamide (DEODA), has been studied. The dependence of the extraction on nitric acid concentration, DEODA concentration and temperature from nitric acid solution has been considered. The extracted species has also been investigated using FT-IR spectrometry. The related themodynamic functions were calculated.     

N,N-二甲基羟胺与HNO2的反应动力学

分别在高氯酸和硝酸介质中研究了N,N-二甲基羟胺(DMHAN)与HNO₂的反应动力学,通过考察溶液酸度、还原剂浓度、离子强度和温度等因素对反应过程的影响,获得高氯酸介质中反应动力学速率方程为-d[HNO₂]/dt=k[DMHAN][HNO₂],在18.5 ℃,离子强度μ=0.73 mol/L时,反应速率常数k=(12.8±1.0) mol/(L·min),反应活化能Ea=41.5 kJ/mol。 在硝酸介质中DMHAN与HNO₂的反应比较复杂,硝酸浓度较高时,硝酸将参与反应重新生成HNO₂,且硝酸浓度越大,HNO₂的生成速度越快,HNO₂与DMHAN的反应是自催化氧化的。 对DMHAN与HNO₂的反应产物进行了分析,并推导了硝酸体系中DMHAN与HNO₂的反应机理。     

Consecutive thin-layer chromatographic separation of Zr(IV), Hf(IV) and many other ions on silica gel in nitric acid-hydrogen peroxide media

The thin-layer chromatographic (TLC) behaviour of 64 ions including Zr(IV) and Hf(IV) has been surveyed on systems composed of silica gel and of nitric acid and nitric acid-hydrogen peroxide media. In the 0.5 mol 1(-1) HNO(3)-3% (w/v) H(2)O(2) solution, only Hf(IV) adsorbed very strongly, whereas Zr(IV) and many other ions showed no or weak adsorption. Stepwise development with diluted nitric acid and subsequently with nitric acid-hydrogen peroxide solution allowed the consecutive separation of three-component mixtures consisting of Zr(IV), Hf(IV) and one of many other accompanying elements, such as Mo(VI), Nb(V), Th(IV), Ti(IV), U(VI) and rare earths(III), to be conducted simply and effectively.     

酸处理对斜发沸石结构影响的研究

采用不同浓度硝酸对斜发沸石（HEU）进行改性处理,结合元素分析（ICP-AES）、N₂物理吸附、X射线粉末衍射（XRD）、魔角旋转固体核磁（MAS NMR）等测试手段及DFT理论计算,研究了酸处理对斜发沸石结构的影响。结果表明,硝酸处理对不同平衡阳离子的HEU（Na-K-HEU、NH₄-HEU、H-HEU）具有不同的脱铝效果。酸处理后Na-K-HEU和NH₄-HEU的硅铝比、比表面积均显著升高。随硝酸浓度增大两个沸石样品的脱铝程度逐渐增加,同时骨架结构也逐渐破坏,硝酸浓度达到4 mol/L时其相对结晶度已低于50%。而H-HEU样品的骨架结构稳定,随硝酸浓度的增大铝含量轻微降低,硝酸浓度达到6 mol/L时相对结晶度仍高达94.8%。阳离子反交换实验结果证明,平衡阳离子的类型不是影响HEU骨架稳定性的主要因素。Na-K-HEU和经硝酸铵交换后的NH₄-HEU中铝都以骨架铝的形式存在,而在后者焙烧成为H-HEU时出现部分非骨架铝,伴随了骨架的稳定化过程。     

The application of novel hydrophobic ionic liquids to the extraction of uranium(VI) from nitric acid medium and a determination of the uranyl complexes formed

Novel ammonium based hydrophobic ionic liquids (ILs) have been synthesised and characterised, and their use in the liquid-liquid extraction of uranium(VI) from an aqueous nitric acid solution using tri-n-butyl phosphate (TBP), studied. On varying the nitric acid concentration, each IL was found to give markedly different results. Relatively hydrophilic ILs showed high uranium(VI) extractability at 0.01 M nitric acid solution which progressively decreased from 0.01 to 2 M HNO(3) and then increased again as the nitric acid concentration was increased to 6 M. An analysis of the mechanisms involved for one such IL, pointed to cationic-exchange being the predominant route at low nitric acid concentrations whilst at high nitric acid concentrations, anionic-exchange predominated. Strongly hydrophobic ILs showed low extractability for nitric acid concentrations below 0.1 M but increasing extractability from 0.1 M to 6 M nitric acid. The predominant mechanism in this case involved the partitioning of a neutral uranyl complex. The uranyl complexes were found to be UO(2)(2+)·(TBP)(3) for the cationic exchange mechanism, UO(2)(NO(3))(2)(TBP)(2) for the neutral mechanism and UO(2)(NO(3))(3)(-)·(TBP) for the anionic exchange mechanism.     

Oxidation of brown coal of Angren deposit with a mixture of nitric and sulfuric acids

Oxidation of brown coal of Angren deposits by a mixture of nitric and sulfuric acids was studied in respect of dependence on the concentration of nitric acid (5–30%), concentration of sulfuric acid in nitric acid solution (2.5–20%), and temperature (40–80°C) at the process duration 2 h and the ratio of coal: HNO₃ = 1: 2. Optimal conditions of the process in terms of maximum yield of humic acids and the minimum loss of nitrogen oxides were found.     

Tri-n-octylphosphine sulfide: : A selective organic extractant

Tri-n-octylphosphine sulfide (TOPS) has been investigated as the stationary phase in reversed-phase partition paper Chromatographie separations using nitric or hydrochloric acids as the mobile phase. TOPS has also been studied as an extractant for metal ions. Silver, mercury (II), and palladium (II) were found to have RF values of zero when nitric acid was used as the mobile phase. These same ions were also selectively extracted from aqueous nitric acid solutions. Gold(III), mercury(II), palladium (II), and platinum (IV) were found to have RF values of zero when hydrochloric acid was used as the mobile phase. However, only gold(III) and mercury(II) were extracted from aqueous hydrochloric acid solutions in liquid-liquid extraction systems. Several separations were successfully performed from 1 M nitric acid.     

Picosecond pulse radiolysis study of highly concentrated nitric acid solutions: formation mechanism of NO3• radical

The formation of nitrate radical, NO(3)(?), is observed for the first time directly by picosecond pulse radiolysis of highly concentrated nitric acid solutions. The experimental yield of NO(3)(-) ionization is deduced from the pulse-probe transient absorption measurements in the visible region where this radical absorbs. On the basis of the value of the extinction coefficient of nitrate radical at 640 nm equal to 1300 M cm(-1), the experimental yield of NO(3)(?) at 20 ps is found to be around 0.36 × 10(-7), 1.33 × 10(-7), and 2.85 × 10(-7) mol J(-1) for 1, 3.5, and 7 M nitric acid solutions, respectively. Relative to the dose absorbed by nitric acid by the direct effect, we find an unexpected high formation yield of the nitrate radical within the electron pulse. Therefore, we suggest that the trapping of the positive hole, H(2)O(?+), by NO(3)(-) also contributes to the formation of NO(3)(?) within the electron pulse. Moreover, after the pulse and within 4 ns, the beginning of the reaction of OH(?) radical with undissociated nitric acid is observed for the most concentrated nitric acid solution.     

Effect of the TBP and water on the complexation of uranyl nitrate and the dissolution of nitric acid into supercritical CO2. A Theoretical Study

We report theoretical studies on the complexation of uranyl nitrate and the dissolution of nitric acid in supercritical CO2 by TBP. According to quantum mechanical calculations, TBP (modeled by trimethyl phosphate TMP) displays stronger hydrogen-bonding interactions with HNO3 than with H2O, and this has been modeled in force-field calculations. Different combinations of water, TBP, and acid are compared in SC-CO2 and simulated by molecular dynamics (MD), demonstrating the importance of TBP and water concentrations. In MD simulations, which started from "random" mixtures of water, TBP, nitric acid, and uranyl nitrate, complexation of uranyl by TBP is observed and the yield increases with the TBP concentration. TBP molecules are also necessary to dissolve nitric acid in the supercritical phase. Indeed, without TBP, nitric acid alone self aggregates via hydrogen-bonding interactions. Adding water to this solution leads to the formation of water microdomains containing the acid and uranyl salts. The simulations show that a high TBP/nitric acid ratio is needed to fully dissolve the acid in the supercritical phase and to form CO2-philic UO2(NO3)2(TBP)2 complexes. The resulting hydrogen-bonding and solvation patterns are analyzed. The results are consistent with experimental observations and provide microscopic views of this important extraction system.     

Extraction of uranyl(VI) ion with N,N-dibutyldodecanamide in toluene

The extraction of U(VI) with newly synthesized long chain alkyl amide, N,N-dibutyldodecanamide (DBDA), in toluene has been studied. The dependence of the extraction on nitric acid and DBDA concentrations and temperature from nitric acid solution has been considered. The extracted species has also been investigated using FT-IR spectrometry. The related thermodynamic functions were calculated. The separation factor between U(VI) and Th(IV) is higher and there is no third phase formation under the conditions studied.     

Kinetic studies on the oxidation of uranium(IV) in nitric acid solution

The kinetics of oxidation of U(IV) in nitric acid solution by nitrous acid and air oxygen have been studied. The effects of concentrations of U(IV), nitric acid, hydrogen ion and nitrous acid in aqueous solution or oxygen in gas on the oxidation rate have been examined. The oxidation rate increases with increasing temperature and the activation energies are 47 kJ mol^–1 for nitrous acid and 91 kJ mol^–1 for oxygen. The mechanisms for both oxidation reactions are discussed.     

P-507回流萃取法富集镥的研究——Ⅰ.P-507萃取分离镱镥混合稀土的性能

本文研究了2-乙基己基膦酸单2-乙基己基酯(P-507)在盐酸和硝酸体系中萃取镱镥混合稀土的性能。说明P-507在硝酸体系中的萃取分离系数较其在盐酸体系中高,而在盐酸体系中有更高的反萃效率。与二(2-乙基己基)磷酸(P-204)相比,P-507具有萃取酸度低、易反萃和不易乳化的优点。我们还确定了回流萃取法分离镥镱的基本参数,表明P-507是一种新型的分离重稀土的良好萃取剂。     

Simultaneous spectrophotometric determination of uranium, nitric acid and nitrous acid by least-squares method in PUREX process

Multi-wavelength linear regression spectrophotometry combined with method of least squares for simultaneous determination of uranium, nitric acid and nitrous acid in PUREX (Plutonium/URanium EXtraction) process was developed. The molar absorbance matrix was calibrated with absorbance data measured in the wavelength range of 350–500 nm for a series of standard solutions by linear least-squares regression. This method used information from the absorption spectra of U(VI)–nitrous acid–nitric acid solutions to determine U(VI), nitrous acid and nitric acid. In the range of 0.95–74.1 g/L U(VI), 5 × 10^?4–2 × 10^?3 mol/L nitrous acid and 3–5 mol/L aqueous nitric acid solution, the measuring precision for determination of U(VI), nitrous acid and nitric acid was 0.46, 4.09, and 0.68 % respectively. In the solution of 30 % TBP–kerosene, the measuring precision for determination of U(VI) and nitrous acid was 0.42 and 4.2 % respectively in the range of 0.95–74.1 g/L U(VI) and 5 × 10^?4–2×10^?3 mol/L nitrous acid. The spectrophotometric method can be valuable for monitoring and controlling of both species in PUREX process operation, thanks to its simplicity, efficiency and accuracy.     

单柱离子色谱法测定一价阳离子的流动相研究

对单柱离子色谱法测定一价阳离子的流动相进行了系统研究，阐述了一价阳离子的保留行为和电导检测行为与流动相之间的关系，分别对无机酸（硝酸）、有机酸（柠檬酸）和芳香碱（苯胺）为流动相测定一价阳离子进行了讨论，其中有机酸和无机酸是较为适宜的流动相。