Soft X-ray spectromicroscopy of humic acid europium(III) complexation by comparison to model substances

To provide the experimental basis for a deeper understanding of humic acid (HA) C 1s-near edge X-ray absorption fine structure (NEXAFS) spectra with and without metal ion complexation, a set of model compounds is investigated. Phthalic acid and hydroxyl substituted benzoic acids (benzoic, 4-hydroxy benzoic, protocatechuic, and gallic acid) are examined in an attempt to describe the C 1s-NEXAFS spectra of more complex organic acids—including HA—based on the building block principle. While the peak assignments and observed oscillator strengths for aromatic and carboxylic groups in these spectra are in good agreement with common assumptions, the spectral intensity in the range of the phenolic band is not readily explained with a simple building block model. The spectral signature observed for HA and Eu(III)–HA complexes is compared to the one obtained for polyacrylic acid (PAA) and Eu(III)–PAA, chosen as model substances for the complexation. In both systems strikingly similar spectral changes going from the uncomplexed to the metal-loaded macromolecules are evident. Therefore, a distinct complexation effect on the C 1s-NEXAFS is postulated. Possible effects of radiation damage on the C 1s-NEXAFS are found to be negligible.     

Humic acid metal cation interaction studied by spectromicroscopy techniques in combination with quantum chemical calculations

Humic acids (HA) have a high binding capacity towards traces of toxic metal cations, thus affecting their transport in aquatic systems. Eu(III)–HA aggregates are studied by synchrotron‐based scanning transmission X‐ray microscopy (STXM) at the carbon K‐edge and laser scanning luminescence microscopy (LSLM) at the ⁵D₀→⁷F_1,2 fluorescence emission lines. Both methods provide the necessary spatial resolution in the sub‐micrometre range to resolve characteristic aggregate morphologies: optically dense zones embedded in a matrix of less dense material in STXM images correspond to areas with increased Eu(III) luminescence yield in the LSLM micrographs. In the C 1s‐NEXAFS of metal‐loaded polyacrylic acid (PAA), used as a HA model compound, a distinct complexation effect is identified. This effect is similar to trends observed in the dense fraction of HA/metal cation aggregates. The strongest complexation effect is observed for the Zr(IV)–HA/PAA system. This effect is confirmed by quantum chemical calculations performed at the ab initio level for model complexes with different metal centres and complex geometries. Without the high spatial resolution of STXM and LSLM and without the combination of molecular modelling with experimental results, the different zones indicating a `pseudo'‐phase separation into strong complexing domains and weaker complexing domains of HA would never have been identified. This type of strategy can be used to study metal interaction with other organic material.     

Tween-80-(NH4)2SO4-XO体系中铜、镧、铀、铈光谱及萃取性能研究

利用二甲酚橙作萃取剂 ,在吐温 80 (NH4 ) 2 SO4 二甲酚橙 (XO)固 液萃取体系中 ,研究了萃取相 (固相 )中金属离子络合物吸收光谱 ,与XO光谱比较 ,Cu(Ⅱ ) ,U(Ⅵ ) ,Ce(Ⅳ )离子吸光度增大 ,最大吸收波长红移 2 0～ 30nm ;La(Ⅲ )离子几乎未变。同时探讨了该体系中不同酸度、不同盐用量、不同萃取剂用量、不同类型表面活性剂 ,对Cu(Ⅱ ) ,La(Ⅲ ) ,U(Ⅵ ) ,Ce(Ⅳ )离子的萃取率的影响 ,在pH 6 0的酸度下 ,实现了La(Ⅲ )与U(Ⅵ )之间的萃取分离。     

Speciation of actinide ions in aqueous solution by laser-induced pulsed photoacoustic spectroscopy

The oxidation-state specific detection of actinide ions, U(VI), Pu(IV), Pu(VI), and Am(III), was investigated by pulsed laser photoacoustic spectroscopy. With a single-beam differential technique, the solvent effect is compensated and thus the detection sensitivity substantially increased. The observed detection sensitivities are8×10^–7M/L for U(VI)7×10^–8M/L for Pu(IV)3×10^–8M/L for PU(VI)2×10^–8M/L for Am(III)The present method facilitates the study of complexation and polymerization of actinide ions in the submicromole concentration range.     

双水相体系中Cu(Ⅱ),La(Ⅲ),U(Ⅵ),Ce(Ⅳ)光谱行为及萃取分离

利用聚乙二醇2000(PEG)-(NH)2SO4-萃取剂(铜试剂)双水相体系,采用液-液萃取的方法,研究了PEG相、单纯水相中金属离子络合物及萃取剂的光谱行为,探讨了金属离子络合物在PEG相中存在形态及萃取机理。同时实验了在不同酸度,不同盐用量,不同萃取剂用量,以及在不同表面活性剂的影响下,铜、镧、铀、铈的萃取率,通过控制一定条件,实现了Cu(Ⅱ)与La(Ⅲ),Cu(Ⅱ)与Ce(Ⅳ)之间的定量萃取分离。     

城市生活垃圾堆肥胡敏酸动态光谱特性研究

利用城市生活垃圾中降解部分,采用工厂化工艺进行堆肥,对堆肥过程中胡敏酸动态光谱特性进行了分析。结果表明,随着堆肥进行,胡敏酸在短波长的荧光强度明显降低,并且主体峰位置发生改 变,逐渐靠近土壤胡敏酸的主峰位置。红外光谱解析显示,胡敏酸结构中多糖类脂类等小分子化合物随着堆肥时间的延长而减少,而芳族类化合则呈增加的趋势。紫外扫描光谱进一步证实,在堆肥过程中 ,胡敏酸分子共轭作用、缩合度增加,腐殖化程度明显。但与土壤胡敏酸的E₄/E₆值、光谱特性比较表明,堆肥后的胡敏酸具有相对简单的分子结构,活性较高。     

Calix Receptor Edifice; Scrupulous Turn Off Fluorescent Sensor for Fe(III), Co(II) and Cu(II)

Novel Supramolecular fluorescence receptor derived from calix-system i.e. calix[4]resorcinarene bearing dansylchloride as fluorophore was designed and synthesized. The compound was purified by column chromatography and characterized by elemental analysis, NMR and Mass spectroscopy. Tetradansylated calix[4] resorcinarene (TDCR) shows a boat conformation with C₂v symmetry. The complexation behaviour of metal cations [Ag(I), Cd(II), Co(II), Fe(III), Hg(II), Cu(II), Pb(II), Zn(II), U(VI) (1?×?10^-4?M)] with tetra dansylated calix[4]resorcinarene (1?×?10^-6?M) was studied by spectophotometry and spectrofluorometry. Red shift in the absorption spectra led us to conclude that there is strong complexation Fe(III), Co(II) and Cu(II) with TDCR. These metal cations also produce quenching with red shifts in the emission spectra. The maximum quenching in emission intensity was observed in the case of Fe(III) and its binding constant was also found to be significantly higher than that of Co(II) and Cu(II). Quantum yield of metal complexes of Fe(III) was found to be lower in comparison with Co(II) and Cu(II) complexes. Stern Volmer analysis indicates that the mechanism of fluorescence quenching is either purely dynamic, or purely static.     

Evaluation of Cyanex 923-coated magnetic particles for the extraction and separation of lanthanides and actinides from nuclear waste streams

In the magnetically assisted chemical separation (MACS) process, tiny ferromagnetic particles coated with solvent extractant are used to selectively separate radionuclides and hazardous metals from aqueous waste streams. The contaminant-loaded particles are then recovered from the waste solutions using a magnetic field. The contaminants attached to the magnetic particles are subsequently removed using a small volume of stripping agent. In the present study, Cyanex 923 (trialkylphosphine oxide) coated magnetic particles (cross-linked polyacrylamide and acrylic acid entrapping charcoal and iron oxide, 1:1:1, particle size=1–60 μm) are being evaluated for the possible application in the extraction and separation of lanthanides and actinides from nuclear waste streams. The uptake behaviour of Th(IV), U(VI), Am(III) and Eu(III) from nitric acid solutions was investigated by batch studies. The effects of sorption kinetics, extractant and nitric acid concentrations on the uptake behaviour of metal ions were systematically studied. The influence of fission products (Cs(I), Sr(II)) and interfering ions including Fe(III), Cr(VI), Mg(II), Mn(II), and Al(III) were investigated. The recycling capacity of the extractant-coated magnetic particles was also evaluated.     

Quantum-chemical calculations of electronic-absorption spectra of aromatic amino acids in aqueous solution

Quantum-chemical methods are used to calculate electronic-absorption spectra, dipole moments, and atomic-charge distributions of aromatic amino acids in aqueous solutions at various concentrations. The electronic-absorption spectra are analyzed and compared with the spectra that are calculated for gas phase. The bathochromic shift of the spectral position is shown for the long-wavelength absorption peak of the singlet-singlet transition for aqueous solutions of amino acids.     

Biosorption and Biomineralization of Uranium(VI) from Aqueous Solutions by Landoltia PunctataSCIEI北大核心CSCD

The biosorption and biomineralization characteristics of uranium by the duckweed Landoltia punctata was investigated in aqueous solutions enriched with 1 to 250 mg . L-1 of U(VI) supplied as uranyl nitrate [UO2(NO3)(2) center dot 6H(2)O]. The maximum uranium removal for the plant cultivar occurred at pH 4 similar to 5 of solution and their uranium removal efficiencies exceeded 90% after 24 h. In kinetics studies, the dried powder of duckweed can finished nearly 80% adsorption within 5 min, the batch adsorption equilibrium can be reached within 24 h for the living and dried powder of duckweed, Both for the living and dried powder of duckweed, the experimental data were well fitted by the pseudo-second-order rate model with the degree of fitting (r) higher than 0.99. The adsorption isotherms could be better described by the Freundlich model than the Langmuir model. In addition, Fourier transform infrared spectroscopy (FTIR) revealed that the surface of Landoltia punctata possess many active groups such as hydroxyl, carboxyl, phosphate and amide groups, the hydroxyl, amino groups involved in adsorption of U(VI) by living and dried powder of Landoltia punctata, and the phosphate groups also participated in the adsorption behavior of U(VI) by the living Landoltia punctata. The living Landoltia punctata reduction part of U(VI) to U(IV) was observed by XPS analysis. SEM and energy dispersive X-ray spectroscopy (EDS) of duckweed from 10 similar to 200 mg . L-1 uranium treatments indeed showed root surface of living Landoltia punctata formed a significant portion of U precipitates with nanometer sized schistose structures that consisted primarily U and P, not containing C. Inorganic phosphate was released by the root cells of Landoltia punctata during the experiments providing ligands for formation of insoluble U(VI) and U(IV) phosphates. The distinct uranium peaks in the EDS spectra of the cluster on the root surface can be observed after biosorption and the uranium and phosphorus mass ratio of the cluster spot was measured to be 82.5% and 8.76% of the total component weight, respectively, and the atomic percentage of 30.89% and 25.19%, respectively. It is worth noting that the phosphorus mass ratio and the atomic rate of the control group is only 0.24% and 0.11%, respectively. But there was no similar crystals observed on the surface of dried powder of Landoltia punctata after biosorption. The present work suggests that living and dried powder of Landoltia punctata can remove more than 90% U(VI) from solution simultaneously precipitated together with phosphate by the living Landoltia punctata, and the dried powder of Landoltia punctata adsorption U(VI) is mainly through the effect of electrostatic attraction, ion exchange and complexation coordination, etc. Here, for the first time, the presence of U immobilization mechanisms within one aquatic plant is reported using Landoltia punctata.     

Structural instabilities and transverse effective charges in IV–VI compounds

Transverse effective charges for some IV–VI, III–V and II–VI compounds are investigated on the basis of the interband electron-phonon coupling with the use of the Penn model for electron energy bands. The results show that the large transverse effective charges of IV–VI compounds are related with strong electron-phonon interaction as well as with the softening of TO phonon in IV–VI compounds.     

Band Displacement Process with Redox Reactions for Uranium Isotope Separation by Chemical Exchange between U(IV)-Resin and U(VI)-Solution

The extreme limits for ²³⁵U/²³⁸U % at ambiant temperature were determined experimentally with a long time band displacement process (almost 1 year) using the isotope exchange reaction between U(IV)_resin and U(VI)_solution. These limits are 0.738 and 0.712, considering ²³⁵U/²³⁸ = 0.725% for natural uranium. The redox reactions, allowing the band displacement were: 1) in front of the band is the reduction of U(VI) in solution by a cathionic resin in Ti(III)-form; 2) in the tail of the band is the oxydation of U(IV) in resin by a solution containing Fe(III) ions.     

Phase diagram of Bi up to 140 kbars

The phase diagram of Bi has been studied by resistometric techniques in the temperature range of 30 to 300°K up to pressures of 140 kbars. Using the original Bridgman phase notation, the phase transitions I–II, II–III, I–III, III–IV and V–VI were observed. Two new phases, designated VIII and IX were observed in this region. The triple points occurring between I–II–III near 29.5 kbars and 160°K, between IV–V–VIII near 55 kbars and 240°K, between V–VI–VIII near 72 kbars and 255°K and between VI–VIII–IX near 135 kbars and 250°K. Earlier measurements were adjusted to the 1970 Drickamer pressure scale and compared to the present results. A phase diagram is proposed for pressures to 140 kbars. Calculations of the volume changes and latent heats of transformation are made near the triple points I–II–III, IV–V–VIII and V–VI–VIII using the measured volume changes of Bridgman for the I–II, IV–V and V–VI transitions. The latent heat associated with the III–IV transition was calculated using the volume data of Bridgman to be less than ? 2 cal/mol.     

腐植酸增值尿素的多谱学分子结构表征

尿素生产过程中加入腐植酸生产腐植酸增值尿素,可以有效延缓尿素水解,提高作物产量与氮肥利用效率,然而在此过程中腐植酸(HA)与尿素(U)主要发生什么反应还未见报道。利用风化煤源HA生产含腐植酸5%, 10%及20%的腐植酸增值尿素(HAU5, HAU10及HAU20),采集并分析了HAU5, HAU10, HAU20及U的红外谱图及其二阶导数谱图,用XPS与O(1s)NEXAFS分别对HAU20, HA及U进行表征;通过无水乙醇溶解HAU20的方式去除了HAU20中的尿素,并利用FTIR与XPS对醇不溶物(UHA)进行表征。结果表明：(1)FTIR原谱图及二阶导数谱图表明,腐植酸增值尿素伯胺C—N振动强度低于普通尿素,且振动强度随着HA添加量的提高而降低,XPS N(1s)与O(1s)NEXAFS检测到HAU20中分别存在较多仲胺氮与非羰基氧,且FTIR发现UHA酰胺特征明显,表明腐植酸增值尿素制备过程中HA与U发生了反应。(2)XPS C(1s)表明,HAU20与UHA羧基碳比例少于HA, FTIR结果表明,UHA中不存在HA中检测到的羧酸C—O—H面内弯曲振动,羧基CO伸缩振动位置发...     

Conversion of a weak organic acid to a super acid in the gas phase

The effects of selected metal ions on the gas‐phase acidity of weak organic acids have been explored using the DFT and Moller–Plesset Perturbation Theory (MP2) calculations. The three organic acids selected for this study were acetic acid (aliphatic), benzoic acid (aromatic), and glycine (amino acid). The acidities of these compounds are compared with the acidity of their Li⁺‐, Na⁺‐, and K⁺‐complexed species. The results indicate that upon complexation with Li⁺, Na⁺, and K⁺ at 298 K, the gas‐phase acidity of acetic acid, for example, varies from 345.3 to 218.8, 230.2, and 240.1 kcal/mol, respectively (i.e., its dissociation becomes much less endothermic). These values indicate that a weak organic acid can be converted to a super acid when it is complexed with an ionic metal. Copyright © 2007 John Wiley & Sons, Ltd.     

Optical activity in mixed-ligand terbium complexes containing 1,2-Benzenedicarboxylic acid and chiral carboxylic acids

The optical activity of Tb(PHT)(L) complexes has been studied by means of circularly polarized luminescence (CPL) spectroscopy, where PHT=1,2-benzenedicarboxylic acid (phthalic acid) and L=L-mandelic, L-aspartic, and L-malic acids. The CPL spectra were characteristic of multidentate bonding, and close examination of the spectra revealed the nature of the metal-ligand bonding. The results obtained have demonstrated that the optical activity experienced by the Tb(III) ion is primarily determined by the nature of the chiral ligand, and that this chirality can be affected by the achiral ligands also bound in the metal coordination sphere.     

Electron transfer spectra of hexahalide complexes

The electron transfer spectra of the chloro, bromo, and iodo complexes of Ru(III), Ru(IV), Rh(III), Pd(IV), Sn(IV), Sb(V), W(VI), Re(IV), Os(III), Os(IV), Ir(III), Ir(IV), Pt(IV), and Pb(IV) are studied and interpreted by group-theoretical methods as transitions of π (and at higher wave-numbers, σ) electrons, mainly localized in the ligands, to the available orbitals of even parity γ ₅, γ ₃ and γ ₁, representing mainly d, d, and s electrons of the central ion. The half-widths and intensities of the bands support the identification. The remarkable similarity between the spectra of d ⁴ and d ⁵ systems with the same set of ligands is explained by the presence of only one effective excited state of the central ion. The structure expected of the group of π transfer bands as function of increasing Landé parameter ζ _np of the halogen is calculated. The use of pure molecular orbital (M.O.) configurations as a convenient classification (but not a very good approximation to the wave-function) is compared to the analogous case of atomic spectroscopy. It is recommended to estimate the M.O. energies from absorption spectra rather than to try to calculate them from unreliable approximations.     

嘉陵江重庆段沉积物中腐殖酸的特性研究

从嘉陵江不同河段沉积物中提取腐殖酸,采用元素分析、傅里叶变换红外光谱(FTIR)和荧光光谱对腐殖酸的化学组成和结构特征进行研究.元素分析显示,腐殖酸样品的H/C,O/C和C/N摩尔比具有明显差别,说明其化学组成和结构特征存在差异.FTIR分析显示,腐殖酸样品的官能团结构相似,含有大量的羧基、羟基、羰基等活性官能团,芳香族结构特征显著.三维荧光光谱(3DEEM)显示,腐殖酸样品在Ex/Em=270/390 nm和Ex/Em=230/350 nm附近出现两个特征峰a和b,其荧光强度Ia/Ib=1.31～2.53,揭示其含有多种类型的荧光发色基团.荧光指数f450/500=1.43～1.53,表明腐殖酸主要以陆源输入为主.