EDTA络合滴定法测定锆英石中的锆铪合量

本文介绍了一种测定锆英石中锆铪合量的EDTA络合滴定法,分析了标准样品及实际样品,并验证了该方法的可行性。结果表明,该方法准确、简单、可行性较强。     

Mechanistic study of hafnium and zirconium extraction with organophosphorus extractants

Research on the purification of Zr has increased in the last few decades and although effective processes have been developed, little is known about the mechanism of Hf and Zr extraction; particularly, at low acid concentrations. This study’s aim was to determine the influence of alterations in alkyl substituents on the extraction mechanism of Hf and Zr from sulfate media. Seven organophosphorus extractants (Dio-PA, TPPA, DPPA, TPPO, TPPS, D2EHPA and Ionquest 801) were screened with four of them (Dio-PA, DPPA, D2EHPA and Ionquest 801) resulting in promising extraction results. This was attributed to the activity of the acidic hydroxy phosphinyl (=P(O)OH) group which is responsible for the dimerization and cation exchange properties of the extractant. The extractant and hydrogen ion stoichiometries involved in the extraction mechanism were determined for these four extractants by slope analysis from extractant- and acid-variation experiments. It was found that Dio-PA, D2EHPA, and Ionquest 801 extract via a cation-exchange mechanism, according to [M(OH)₂]²⁺ + 2 HA ? M(OH)₂A₂ + 2 H⁺. In contrast, the extraction with DPPA was best described by a solvated cation exchange (SCE) mechanism, according to [M(OH)]³⁺ + 6 HA ? M(OH)A₃.3HA + 3 H⁺. It was concluded that the presence of electron-withdrawing substituents produced softer Lewis base extractants, which favored the extraction of Hf over Zr from acidic sulfate media.     

钛,锆,铪取代的膦叶立德的合成及应用

简介了ⅣＢ族金属－钛、锆和铪取代的膦叶立德的各种合成方法及它们与酮、醇和一氧化碳的反应。     

Anodic growth of passive films on zirconium and hafnium

Galvanostatic potential-time curves on passive zirconium and hafnium electrodes are recorded and analysed in the light of the Cabrera—Mott equation and the high-field ion migration equation. For both metals, the kink-site density in the reacting metal surface (s) and the oxygen vacancy density in the passive film at the metal—oxide interface (N_o) appear to attain steady values which depend on the current density of metal oxidation (j) according to d log s/d log j ≈ 1/2 and d log N_o/d log j ≈ 3/4. Possible effects of space charge in the passive film are considered and found to be negligible under the conditions covered. Comparisons are made to the corresponding behaviour of some other passive metals and to the anodic dissolution of some active metals.     

D296树脂分离锆、铪洗脱的效果

介绍了在离子交换固定床上用D296强碱性阴离子交换树脂分离锆、铪的洗脱实验研究。吸附与洗脱实验的温度均控制在2~5℃,洗脱实验在饱和吸附的离子交换柱、过漏的离子交换柱、未过漏的离子交换柱中进行。研究结果表明:离子交换柱吸附状态以及洗脱剂酸度对分离效果有显著的影响。当离子交换柱存在交换区时,用任何酸度的硫酸作为洗脱剂,铪均被先洗脱出来,但高酸度的洗脱剂对分离锆、铪更有利;当离子交换柱为饱和状态时,低酸度和高酸度的洗脱剂洗脱,锆、铪不能得到分离。实验证明了单一的固定床分离锆、铪的效率低,要成功实现锆、铪的分离,需采用连续分离的离子交换移动床。     

邻碘苯甲酸铵循环去除粗氧化钪中的锆和铪

锆、铪与钪物理化学性质相似且难以分离,是导致氧化钪纯度不高的主要原因之一。为解决这一问题,本文采用邻碘苯甲酸铵作为沉淀剂,去除粗氧化钪中的锆、铪杂质,通过优化不同实验参数得到最佳工艺条件。在实验研发基础上本工艺进行工业生产,进一步验证及完善了工艺条件。得出在溶液酸度为0.1mol/L、沉淀剂加入量为理论量的1.1倍、100℃保温条件下搅拌30min时处理效果最佳。利用氨水与锆、铪沉淀反应回收沉淀剂,通过FTIR和SEM对锆和铪原沉淀与现沉淀进行表征,高效液相色谱对滤液进行分析,结果表明原沉淀物反应生成氢氧化物和邻碘苯甲酸铵。工业实验中钪和邻碘苯甲酸铵回收率分别为99.54%和95.19%,锆、铪去除率均为99.6%。     

锆及锆合金管道焊接技术探讨

在对锆及锆合金材料焊接性能进行分析的基础上,通过焊接试验研究,摸索和总结出锆及锆合金管道焊接工艺,制定相应的焊接工艺评定,为锆及锆合金材料的焊接积累了丰富的经验。     

锆/铪基催化剂催化转移加氢反应的研究进展

催化转化是可再生生物质资源利用的重要途径,高效催化剂的构建是生物质及其衍生物催化转化的关键环节.生物质衍生羰基类化合物加氢转化为醇或酯类化合物是生物质催化转化利用过程中重要的反应步骤.由于氢转移加氢反应过程具有反应条件温和的优点,因此非均相氢转移加氢催化剂在羰基类生物质平台分子转化中得到广泛应用.过渡金属锆、铪是常用的...     

高纯氯氧化锆和二氧化锆的制备

研究了工业氯氧化锆重结晶制备高纯氯氧化锆的过程，通过选择，确定氯氧化锆溶液浓度为160g/L，结晶酸度为5.5-6.0mol/L，煅烧过程中盛装高纯氯氧化锆匣钵为石英匣钵，从而得到产品纯度为99．9％的高纯二氧化锆。     

压力容器用锆及锆复合板的特性与应用

简述压力容器用锆材优异的耐腐蚀性能，分析锆／钢复合板的爆炸复合固体焊接技术与特性，提出质量控制要点，对其在化工设备中的应用进行简要介绍。     

锆和锆合金在化工设备中的应用

介绍锆和锆合金的性能及在设计、制造、检验中的特点。     

Pyrolysis—gas chromatography of Australian coals. 2. Bituminous coals

Pyrolysis—gas chromatography (Py—g.c.) was used to characterize quantitatively a series of high- to low-volatile bituminous Permian Australian coals. The levels of n-alkanes, n-alkenes and triterpenoids released by pyrolysis all decrease as a function of increasing rank and thus, the coal samples can be classified into three distinct groups. Carbon Preference Indices (CPI's) for alkanes and alkene/alkane ratios also decrease as a function of rank. The triterpenoids have exclusively the hopane skeleton. The hopane isomeric distributions exemplify the geological maturity of bituminous coals relative to brown coal (lignite). A significant correlation has been established between the level of n-alkanes and n-alkenes released under Py-g.c. conditions and the predicted oil yield by pyrolysis of these coals. Further development and application of the techniqueshould enable much to be learnt relating to the quality and yield of flash pyrolysis tars as well as the original coal macromolecular structure.     

Selective Biosorption of Zirconium and Hafnium from Acidic Aqueous Solutions by Rice Bran,Wheat Bran and Platanus Orientalis Tree Leaves

Abstract

The Zr(IV) and Hf(IV) biosorption characteristics of rice bran, wheat bran and Platanus orientalis tree leaves were examined as a function of initial pH, contact time, temperature, and initial metal ions concentration. Adsorption equilibriums were achieved in about 1, 5 and 40 min for rice bran, wheat bran, and leaves respectively. The biosorption behavior of leaves was significantly affected by solution pH whereas rice bran and wheat bran adsorption efficiencies were slightly affected by solution pH. The Freundlich and Langmuir adsorption equations, which are commonly used to describe sorption equilibrium for metals removal by biomasses, were use to represent the experimental and equilibrium data fitted well to the Langmuir isotherm model. The negative Gibbs free energy values obtained in this study with rice bran wheat bran and Platanus orientalis tree leaves confirmed the feasibility of the process and the spontaneous nature of sorption. In the optimum conditions, the adsorption efficiencies of other metal ions such as Fe³⁺, Cu²⁺, Pb²⁺, Hg²⁺, La³⁺, Ce³⁺ were significantly lower than Zr(IV) and Hf(IV) ions and these biomasses are excellent sorbents for the selective uptake of proposed ions from acidic aqueous solutions.     

Direct determination of organic sulphur in raw and chemically desulphurized coals

An electron beam technique has been developed for the direct determination of organic sulphur in coal, using a scanning electron microscope coupled with an energy-dispersive X-ray analysis system with quantitative data reduction capabilities. The direct measurement of organic sulphur is performed on a number of particles of the maceral vitrinite, previously located within the mounted coal sample by reflected light microscopy. The particles are first examined by SEM at ≈5000 × magnification to allow proper identification of most mineral inclusions and to avoid these areas during analysis. The X-rays generated from an area 3 μm in diameter are monitored quantitatively by EDX for sulphur and iron, as well as for calcium, aluminium and silicon. After ensuring that no other elements, indicating mineral matter, are present at the point of analysis, the sulphur value obtained is taken as a measure of the organic sulphur in coal. The results obtained by this technique also allow estimation of the intra- and inter-particle variation in the organic sulphur level. Statistical methods can be used to construct confidence bands about the mean sulphur levels and estimate standard deviations within and between particles. This permits evaluation of the precision of the analysis on a sample-by-sample basis and provides a measure of the heterogeneity of the coal. The SEM-EDX method has been applied to a large number of raw coals and coals chemically desulphurized by the Ames, PETC and Ledgemont oxydesulphurization processes, as well as the molten caustic (Gravimelt) process of TRW Systems Inc. The results of this direct technique agree fairly well with those of the ASTM procedure, for both raw and chemically processed coals, although for the latter the SEM values often show less desulphurization than the ASTM values.     

Trace element geochemistry of the Obed Mountain deposit coals, Alberta, Canada

This study reports on the elemental concentrations and vertical variation of coal seams from the Obed Mountain deposit, Alberta Foothills, Canada. Results from two sections of Seam 1 show that the major elements (i.e. Al, Fe, Mg, K, Na, Ti, and Si) have high concentrations in intervals having high ash content, with the only exception of Ca. Similarities are apparent, in both sections, in the vertical variations of Th, U, Se, and Zn; Rb, Cs, and K; Sb, Mo, and W; Mn and Sr; and Ba, Cr, Co, Hf, and Sc. These similarities are also evident among the REEs, notably between Ce and La; also between Dy, Eu, and Sm. Most elements, with the exception of Ba and Sr are slightly more concentrated in Section 2 of Seam 1, located approximately 1.5Fig. km away from Section 1. Compared to Seam 1, Seam 2 has lower mean concentrations of elements. Boron in the coal ranges from 27 to 100 ppmw, though most values are less than 50 ppmw. Boron concentrations suggest a freshwater depositional environment. The element is depleted in the sedimentary partings (12–29 ppmw only) and is enriched in the coal interval near the roof and immediately beneath the partings. This enrichment shows possible downward mobilization of boron. Vertical variations of elements are helpful in delineating the boundaries between coal and sedimentary partings in the succession. The Obed Mountain coals are “clean” by world standards and their elemental concentrations are comparable with those in coals of a lower rank from the same coal formation used for power generation in Alberta. All sedimentary partings have low concentrations of Ba, Hf, Sc, Sr, Ta, Th, U, and REEs; this, along with the absence of an Eu negative anomaly suggests a non-volcanic origin for the partings.     

Ultimate analysis of coals and cokes using instrumental techniques

This Paper describes instrumental techniques for the rapid determination of carbon, hydrogen, nitrogen, oxygen and sulphur. Two Perkin-Elmer Model 240 elemental micro-analysers were used, one for the direct determination of oxygen and the other for the simultaneous analysis for carbon, hydrogen and nitrogen. The Leco Automatic Sulphur Titrator was used for the sulphur assay. Accuracy and repeatability similar to that obtained by the classical methods described in the relevant British Standards were found, and data are presented to illustrate the comparison. Special aspects of developed procedures are emphasized which are essential for the attainment of good precision and accuracy.     

Zirconium oxycarbides and oxycarbonitrides: A review

Zirconium oxycarbides and zirconium oxycarbonitrides are high-temperature ceramic materials with great potential for applications in advanced technologies due to their good refractoriness, mechanical and thermoelectric properties, and corrosion resistance. The properties of ZrCO(N) materials strongly depend on their composition. However, the stoichiometry of stable ZrCO(N) compounds, synthesis chemistry, and thermodynamics of the proceeding reactions require clarification. This review comprehensively interprets data for ZrCO and ZrCON ceramics, including studies that may not have been addressed in prior reviews. It summarizes the state-of-the-art synthesis procedures involving reactions between commonly used zirconia, zirconium carbide, and carbon black, along with other zirconium sources widely used in the last few decades for the preparation of ZrCO(N) materials. The controversial reaction mechanisms of carbothermal reduction of zirconia and the role of CO gas in this process are discussed. The properties of ZrCO and ZrCON and their possible applications are also summarized.     

Extraction of Zirconium and Hafnium in Polyethylene Glycol‐Based Aqueous Biphasic System

Abstract

The behavior of zirconium and hafnium in PEG 2000‐Na₂SO₄‐HCl aqueous biphasic system has been investigated. The dependences of HCl concentration (0.185–0.55 M), extraction temperature (298–318 K), and extraction time (5–120 min) on distribution ratios have been determined. Extraction of this metals in PEG 2000‐Na₂SO₄‐H₂SO₄ and PEG 2000‐Na₃Cit‐HCl systems has been also studied. The sulfate and citrate complexes of Zr and Hf prefer salt‐rich phase in contrast to chloride complexes which pass into PEG rich phase in about 50% (w/w) to the greatest degree in room temperature and at short extraction time. The increase of distribution ratios (D*_Zr=3.75, D*_Hf=4.31) was observed after addition of water soluble organic ligand ‐ tiron (4,5‐dihydroxy‐m benzenedisulfonic acid disodium salt). The results obtained in studied conditions are not very useful for the separation of zirconium and hafnium.     

Flow adsorption calorimetry of coals before and after heat and oxidation treatment

Flow microcalorimetry has been used to determine the heats of preferential adsorption of n-butanol and ammonium hydroxide on a number of coals immersed in n-heptane and water respectively. The determinations have also been carried out on the coals subjected to heating in air to temperatures ranging from 100 °C to 200 °C, to illustrate how the calorimetric technique can detect changes in the surface properties of the coals subjected to various treatments. The heats of adsorption have provided information on the relative surface acidities and hydrophobicities of the coals.     

Study of sulphur in Assam coals by X-ray photoelectron spectroscopy

X-ray photoelectron spectroscopy (XPS) has been used to study the nature and content of sulphur contained in coal samples from Assam. In each case two sulphur 2p (S 2p) peaks were observed. The 169–171 eV 2p peak corresponds to sulphate, whilst the 164–165 eV peak is assigned to S in iron sulphide compounds such as pyrite, marcasite, etc. and also organic sulphur. The complete absence of a 169–171 eV S peak from a coal sample from which both pyritic and sulphate sulphur were removed by hydrodesulphurization strongly indicates that the remaining 164.7 eV S 2p peak corresponds to the total organic sulphur present in the coal.