铌与钽的纸色层分离

本文讨论一种上行纸色层技术——“连续挥发”法.使用此法即使在分析溶液浓度很高时,仍可使欲淋洗元素集聚于色谱上端的狭窄部位.应用此法分离铌与钽,并比较各种含氧有机溶剂的分离效能.在铌钽含量接近时,最适展开剂成分为丙酮:水=91∶9(V/V).使用丙酮与乙醚(水饱和)之混合液作展开剂,可从纯铌中析出微量钽杂质.     

纸上层析分离-ICP-AES测定稀有金属矿中的铌钽

采用HF、HNO_3溶解样品,纸上层析分离富集铌、钽,焦硫酸钾分解铌钽氧化物,酒石酸浸取,ICP-AES测定稀有金属矿中铌钽。研究了溶样用酸、色层分离展开剂比例及展开温度、焦硫酸钾用量、酒石酸浓度等对测定结果的影响,结果表明,采用纸上层析法可使铌钽与其他干扰元素彻底分离,焦硫酸钾熔融后,用酒石酸浸取使铌、钽完全进入溶液,以电感耦合等离子体光谱仪(ICP-AES)进行测定。在20 g/L的酒石酸介质中,ICP-AES测定铌钽的线性范围为0~50μg/mL,检出限为铌0.14μg/mL,钽0.16μg/mL;相对误差小于8%,精密度(RSD)小于6%,可测定矿石中0.001%~40%的Nb_2O_5,Ta_2O_5。该方法可同时测定稀有金属矿中铌钽原矿、精矿及尾矿中铌钽的含量,适合基体复杂、含量差别大的批量样品的检测。     

铌钽分离方法

铌钽的分离以及铌钽的富集与其伴生元素的分离是铌钽分析化学中引人注目的课题。本文根据铌钽的性质,着重引用近十年来有关铌钽的分离方法及其机理研究的主要结果,系统地总结、介绍了铌钽分离方法,並对铌钽分离的理论基础和规律性作了充分讨论,概述了铌钽分离方法的发展。     

圆形纸层析法的研究Ⅷ.铌和钽的分离

利用纸层析法分离铌和钽,前人已有报导,其中丁酮-氢氟酸是一个分离铌和钽的有效展开剂.但因需用非玻璃设备,以致往往受到限制.为此,我们进行了寻找新展开剂的探索,根据这两个元素的络合性质,选用了硫氰酸钾、柠檬酸、酒石酸、盐酸羟胺等作为络合剂,用丙酮、丁酮和戊酮的盐酸溶液以圆形纸层析法进行展开.结果找出(1)丙酮-盐酸-硫氰酸钾(10%)(8:1:2.5)和(2)丙酮-盐酸-柠檬酸(10%)(8:1:1)两种混合液都是分离铌和钽的良好展开剂.     

标准加入法测定铀铌陶瓷材料中微量钽的研究

采用标准加入-ICP/AES法对铀铌陶瓷材料中微量钽的测定进行了研究.当试液中铌的质量浓度为1.0 mg/mL,钽的测定范围是50～500 μg/g,回收率为106%～99.6%,相对标准偏差（RSD）为6.6%～3.1%.     

铌钽溶液的性质及其反应特性

有关铌钽的分析化学研究成果已有专著和述评加以介绍。本文试图从铌钽溶液的某些性质及其反应特性来论述铌钽的某些分析化学反应的规律性。一、铌钽的无机配位络合物铌钽在氢氟酸溶液中形成非常稳定的络合离子,而且具有“真溶液”的性质。根据对 Nb_2O_5-HF-KF-H_2O 和 Ta_2O_5-HF-KF-H_2O 体系的     

电感耦合等离子体原子发射光谱(ICP-AES)法测定尼日利亚铌钽锂矿石中的铌、钽、锂

经过三种样品前处理实验对比,选择采取氢氟酸-高氯酸-王水溶样,酒石酸-王水浸取,电感耦合等离子体原子发射光谱(ICP-AES)法测定尼日利亚地区铌钽矿石中铌、钽、锂元素。对元素的分析谱线、酒石酸浓度等工作条件进行了优化,选择各元素的最佳分析谱线,并进行加标回收实验,探讨了各元素的加标回收率。选取Nb 269.7 nm、Ta 240.0 nm、Li 670.78 nm作为仪器分析谱线,计算得到的方法检出限分别为:Nb 0.5μg/g、Ta 1.5μg/g、Li 15.0μg/g。对比各种溶样方法,选取一种最简洁方便的样品前处理途径,经国家一级标准物质GBW07153、GBW07155和GBW07185验证,测定值的相对误差为-2.82%~1.77%,方法精密度(RSD,n=6)为0.11%~1.2%,测定尼日利亚地区铌钽锂矿石中的铌、钽、锂元素,结果无显著性差异,方法能够满足尼日利亚铌钽矿石中相关组分的准确测定。     

铌与钽中杂质的测定

铌与钽因在原子能工业等新技术部门应用已日见其重要,近年冶金生产增长甚为迅速,工业对其纯度要求亦日益提高。相应有关二元素的分析方法研究亦迅速发展,各国文献中陆续出现铌钽分析化学专题综述,唯有关纯铌与钽中杂质的测定方法尚缺乏总结。为进一步解决纯金属铌、钽的制备问题,并深入研究其性能及在各技术部门的应用,必须解决有关纯金属分析问题。本文简要回顾此一领域内已累集的文献资料,以便于将有关方法应用于实际分析工作,并对尚待解决的问题进行进一步的研究。铌钽分析化学奠基者席勒(Schoeller)在其经典研究中已注意纯化合物中杂质的测定问题。唯直至四十年代以前,工业对铌、钽及其他稀有金属未曾提出     

电感耦合等离子体原子发射光谱(ICP-AES)法测定尼日利亚铌钽锂矿石中的铌、钽、锂

经过三种样品前处理实验对比,选择采取氢氟酸-高氯酸-王水溶样,酒石酸-王水浸取,电感耦合等离子体原子发射光谱(ICP-AES)法测定尼日利亚地区铌钽矿石中铌、钽、锂元素。对元素的分析谱线、酒石酸浓度等工作条件进行了优化,选择各元素的最佳分析谱线,并进行加标回收实验,探讨了各元素的加标回收率。选取Nb 269.7nm、Ta 240.0nm、Li 670.78nm作为仪器分析谱线,计算得到的方法检出限分别为:Nb 0.5μg/g、Ta 1.5μg/g、Li 15.0μg/g。对比各种溶样方法,选取一种最简洁方便的样品前处理途径,经国家一级标准物质GBW07153、GBW07155和GBW07185验证,测定值的相对误差为-2.82%～1.77%,方法精密度(RSD,n=6)为0.11%～1.2%,测定尼日利亚地区铌钽锂矿石中的铌、钽、锂元素,结果无显著性差异,方法能够满足尼日利亚铌钽矿石中相关组分的准确测定。     

薄层色层在无机分析中的应用——Ⅲ.铌和钽及贵金属的分离

seiler曾作阳离子三、四组,碱金属,卤素,各种磷酸根,以及铜、钴、镍、铀和镓的分离及检定^[1]。作者亦曾研究钛、锆、钍、钪、铌和铀的分离^[2],吴孟炎曾作金、银、硒和碲的分离,均获良好效果。本文报告用反相两种方式研究铌和钽及贵金属的薄层层析行为。铌和钽及贵金属分离良好。铌和钽分离后经光谱检查铌中无钽,钽中无铌。此外,还比较铌、钽的薄层与纸层析。     

Separation and simultaneous determination of niobium and tantalum in steel by reversed-phase high-performance liquid chromatography using 2-(2-pyridylazo)-5-diethylamino phenol as a pre-column derivatizing reagent

A method for the simultaneous determination of Nb and Ta in steel and alloy by reversed-phase high-performance liquid chromatography (RP-HPLC) was proposed. 2-(5-Bromo-2-pyridylazo)-5-diethylamino phenol (5-Br-PADAP) was used as a pre-column chelating agent to form a ternary complex with Nb(V) and Ta(V) and tartaric acid. The ternary complexes of Nb(V) and Ta(V) were eluted within 8 min on a C₁₈ column with a mobile phase of methanol-water (55:45, v/v) containing 10 mmol l⁻¹ acetate buffer (pH3.5) and determined with spectrophotometric detection at 598 nm. The detection limits for Nb(V) and Ta(V) were 0.60 and 0.72 μg l⁻¹, respectively, when the ratio of signal-to-noise is 3. The proposed method was used to analyze Nb and Ta in cast iron, alloy and stainless steel.     

铌-(5-Br-PADAP)-羟基酸体系混合型络合物的研究

在酒石酸、柠檬酸、草酸和其它羟基酸存在时,研究了铌和2-[(5-溴-2-吡啶)偶氮]-5-(二乙氨基)苯酚(简称5-Br-PADAP)的反应。发现在酒石酸(Tar)存在时,使用5-Br-PADAP测定铌得到最好的结果。本文用吸光光度法研究蓝色的铌-(5-Br-PADAP)-Tar的混合型络合物。在PH为1.0-4.0范围600毫微米处,此蓝色络合物有最大的吸收。摩尔吸光系数是5.7×10⁴。用两种不同的方法研究混合型络合物的组成,Nb:5-Br-PADAP:Tar=1:1:1。在pH为1.0时,Nb的浓度1-32微克/25毫升范围内遵从比尔定律。本文提出高灵敏度和高选择性的吸光光度法测定合金钢中的微量铌。     

Determination of V(V), Nb(V) and Ta(V) as their 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol chelates by reversed-phase HPLC

This paper reports the separation and determination of V(V), Nb(V) and Ta(V) by RP-HPLC using 5-Br-PADAP as a precolumn derivatizing reagent. On C(18) column, the three metal chelates can be separated on a baseline in 9 min with the mobile phase of methanol-water (59:41, v/v) containing tartaric acid (0.2%) and acetate buffer (pH 3.5, 10 mM). The detection limits of V(V), Nb(V) and Ta(V) are 0.13 ppb, 0.22 ppb and 1.79 ppb, respectively when S/N is 3. This method is simple and rapid, and has been used in mineral analysis with satisfactory results.     

Electrochemical and spectroscopic studies of the chloro and oxochloro complex formation of Nb(V) and Ta(V) in NaCl-AlCl3 melts

The equilibrium constant for the chloro complex formation of Nb(V) NbCl6-<--->NbCl5+Cl- (i) in NaCl-AlCl3 melts at 175 degrees C was found to be pKi = 2.86(5). The oxochloro complex formation of Nb(V) and Ta(V) in NaCl-AlCl3 melts at 175 degrees C could be explained by the following equilibria: MOCl4- <-->MOCl3+Cl- (ii) MOCl3<-->MOCl2(+)+Cl- (iii) where M = Nb and Ta. The equilibrium constants determined by potentiometric measurements with chlorine-chloride electrodes were, for M = Nb, pKii = 2.21(4) and pKiii = 3.95(5) and, for M = Ta, pKii = 2.743(15) and pKiii = 4.521(13). NbCl6- has two bands in the UV-vis region, a strong one at 34.7 x 10(3) cm-1 and a weaker one at 41.6 x 10(3) cm-1. The MOCl4- complexes showed in the case of Nb(V) absorption bands at 32.7 and 42.9 x 10(3) cm-1 and in the case of Ta(V) at 38.6 and 48.1 x 10(3) cm-1.     

室温下空气与金属铌和钽表面的相互作用

用XPS角分布法研究了铌和钽在室温下与干燥空气的相互作用.结果表明铌和钽表面生成了化学组成分别为Nb_2O_5和Ta_2O_5的氧化物,氧化膜内金属原子和氧原子呈混合状态,从而排除了这种相互作用仅仅是化学吸附的可能性.     

主成分-偏最小二乘分光光度法同时测定饲料中的痕量铁、锰、铜、锌

痕量Fe^3＋、Mn^2＋、Cu^2＋、Zn^2＋与2-（5-溴-2-吡啶偶氮）．5-二乙氨基苯酚（5-Br-PADAP）和对．（1,1,3,3．四甲基丁基）苯基醚（Triton X-100）在pH8．3发生高灵敏显色反应,所形成的三元胶束络合物的吸收光谱严重重叠。本文采用主成分-偏最小二乘法（PC—PLS）辅助分光光度法成功地测定了合成试样及饲料中上述4种痕量组分。结果表明,PC—PLS法是化学计量学法中一种可适用于基体较复杂的实际试样中痕量组分同时分光光度测定的优良的多元计算方法。     

Determination of fosfomycin by indirect spectrophotometric method

2-(5-Bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) is a sensitive photometric reagent for determination of zirconium, when fosfomycin is added, it can quantitatively replace 5-Br-PADAP by complexing with zirconium, thus, an indirect spectrophotometric method based on ligand exchange has been established. The detection wavelength is at 605 nm, and the apparent molar absorption coefficient was found to be 4.59x10(4) l mol(-1) cm(-1). Beer's law is obeyed in the range of 0-28x10(-6) M. The composition and stability constant of zirconium with 5-Br-PADAP and with fosfomycin has also been estimated. The proposed method is simple and reproducible, it was applicable to the analysis of fosfomycin from pharmaceutical manufacture.     

Probing the electronic structure of early transition-metal oxide clusters: polyhedral cages of (V2O5)n(-) (n = 2-4) and (M2O5(2)(-) (M = Nb, Ta)

Vanadium oxide clusters, (V2O5)n, have been predicted to possess interesting polyhedral cage structures, which may serve as ideal molecular models for oxide surfaces and catalysts. Here we examine the electronic properties of these oxide clusters via anion photoelectron spectroscopy for (V2O5)n(-) (n = 2-4), as well as for the 4d/5d species, Nb4O10(-) and Ta4O10(-). Well-resolved photoelectron spectra have been obtained at 193 and 157 nm and used to compare with density functional calculations. Very high electron affinities and large HOMO-LUMO gaps are observed for all the (V2O5)n clusters. The HOMO-LUMO gaps of (V2O5)n, all exceeding that of the band gap of the bulk oxide, are found to increase with cluster size from n = 2-4. For the M4O10 clusters, we find that the Nb/Ta species yield similar spectra, both possessing lower electron affinities and larger HOMO-LUMO gaps relative to V4O10. The structures of the anionic and neutral clusters are optimized; the calculated electron binding energies and excitation spectra for the global minimum cage structures are in good agreement with the experiment. Evidence is also observed for the predicted trend of electron delocalization versus localization in the (V2O5)n(-) clusters. Further insights are provided pertaining to the potential chemical reactivities of the oxide clusters and properties of the bulk oxides.     

An aqueous route to [Ta6O19]8- and solid-state studies of isostructural niobium and tantalum oxide complexes

A new soft chemical route to [Ta6O19]8- has been developed by the dissolution of [Ta(O2)4]3- in conditions alkaline enough to arrest formation of Ta2O5, followed by [VO4]3--catalyzed decomposition of the peroxide ligands and crystallization of the salt. An average of bond lengths and angles from isostructural salts of [Ta6O19]8- and [Nb6O19]8- indicate there is an increase in terminal M(eta=O) bond lengths and M-micro2-O-M angles and a decrease in bridging micro2-O-M bond lengths in [Ta6O19]8-, although the central micro6-O-M bond lengths are identical within experimental error. Two new structures of Na7[HNb6O19].15H2O () and Na8[Ta6O19].15H2O () are exemplary of the fact that protonated micro2-OH are observed exclusively in the niobates. In these structures, the metal-oxide framework, seven sodium atoms, and all fifteen water molecules are located in identical unit cell positions, but in an eighth charge-balancing sodium is located in close proximity to the protonated micro2-OH in . Differences in the basicity of Nb(v)- and Ta(v)-bound oxygen atoms are also manifested at the surfaces of 17O-enriched powders of Nb2O5 and Ta2O5. Oxygen exchange at the surface of these materials readily takes place at both terminal and bridging sites in Nb2O5 but only at terminal sites in Ta2O5.     

Stoichiometric and oxygen-rich M2O(n)- and M2O(n) (M = Nb, Ta; n = 5-7) clusters: molecular models for oxygen radicals, diradicals, and superoxides

We investigated the structures and bonding of two series of early transition-metal oxide clusters, M(2)O(n)(-) and M(2)O(n) (M = Nb, Ta; n = 5-7) using photoelectron spectroscopy (PES) and density-functional theory (DFT). The stoichiometric M(2)O(5) clusters are found to be closed shell with large HOMO-LUMO gaps, and their electron affinities (EAs) are measured to be 3.33 and 3.71 eV for M = Nb and Ta, respectively; whereas EAs for the oxygen-rich clusters are found to be much higher: 5.35, 5.25, 5.28, and 5.15 eV for Nb(2)O(6), Nb(2)O(7), Ta(2)O(6), and Ta(2)O(7), respectively. Structural searches at the B3LYP level yield triplet and doublet ground states for the oxygen-rich neutral and anionic clusters, respectively. Spin density analyses reveal oxygen radical, diradical, and superoxide characters in the oxygen-rich clusters. The M(2)O(7)(-) and M(2)O(7) clusters, which can be viewed to be formed by M(2)O(5)(-/0) + O(2), are utilized as molecular models to understand dioxygen activation on M(2)O(5)(-) and M(2)O(5) clusters. The O(2) adsorption energies on the stoichiometric M(2)O(5) neutrals are shown to be surprisingly high (1.3-1.9 eV), suggesting strong capabilities to activate O(2) by structural defects in Nb and Ta oxides. The PES data also provides valuable benchmarks for various density functionals (B3LYP, BP86, and PW91) for the Nb and Ta oxides.