多羧基咪唑离子液体的酸性表征

通过电位滴定法测得多羧基咪唑离子液体的离解常数pKa值(25 ℃)在1.43～1.92范围内, 说明多羧基咪唑离子液体酸性接近乙二酸, 比丁二酸以及乙酸强. 由于多羧基咪唑离子液体结构中咪唑环具有较强的吸电子诱导效应, 使多羧基咪唑离子液体具有中等强度的酸性. 三羧基咪唑离子液体酸性比含相同阴离子的二羧基咪唑离子液体酸性强. 阳离子相同、阴离子不同的多羧基咪唑离子液体酸性强弱顺序为: HSO4－ ＞ NO3－ ＞ PF6－ ＞ H2PO4－＞ Cl－、Br－ ＞ CF3CO2－ ＞ BF4－ ＞ CF3SO3－. 同时, 吡啶红外光谱探针法研究表明, 多羧基咪唑离子液体具有Brønsted酸性.     

不同脱铝深度稀土超稳Y沸石的酸性质

用FT-IR和NH_2-TPD研究了稀土含量相同时脱铝程度不同的四种REUSY沸石的酸性质. 并对复杂羟基谱的归属进行了讨论. 同时将酸性质与骨架的Si、Al分布, 非骨架组份以及二次孔相关联, 提出浅、中度脱铝时主要脱除与超笼中HFOH相关联的Si(3Al)和Si(2Al)单元中的Al, 深度脱铝时则脱除与六方柱笼和方钠石笼中LFOH 羟基相关联的Si(1AI)中的铝和少量Si(2Al)中的铝. 另外发现, 非骨架组份使一部分HFOH羟基不能被吡啶分子接近. 而二次孔的形成使一部份LFOH 能被吡啶分子接近. 随着脱铝深度的加深, 总酸、B酸、L 酸量都减少. 但强酸和B酸的强度均相应增加.     

Flow‐Injection Chemiluminometric Analysis of Thyroxine Hormone in a KMnO,4‐Na2SO3 System

An analytical method consisting of flow injection sampling and chemiluminescence detection for the determination of thyroxine hormone is described. It is based on the weak chemiluminescent reaction of KMnO₄ ‐ Na₂SO₃ in acidic medium, which is enhanced by the addition of thyroxine hormone. The chemiluminescence intensity was correlated linearly with concentration of thyroxine in the range of 1.0 × 10^?7 – 2.0 × 10^?6 mol L^?1 (r² = 0.9976) with a relative standard deviation (n = 4) in the range of 1.0 – 1.9%. The limit of detection (3σ blank) is 5.0 × 10^?9 mol L^?1 with a sample throughput of 180 h^?1. The method has been applied to the determination of thyroxine in pharmaceutical preparations and the results are in good agreement with the value reported. Metal and non‐metal ions and some organic compounds commonly present in tablets and some amino acids were also studied for thyroxine determination.     

Solute-solvent effects in the acidic dissociation of the ampholyte N-tris(hydroxymethyl)methylglycine (“tricine”) in 50 mass % methanol-water solvent

The pK values for the two acidic dissociation steps of the ampholyte N-tris-(hydroxymethyl)methylglycine (tricine) in 50 mass % methanol-water solvent have been determined by emf measurements of cells of the type Pt|H₂(g, 1 atm), tricine buffer, Br^–, AgBr|Ag over the range 5 to 50°C (pK ₁)and 5 to 60°C (pK ₂).The standard thermodynamic quantities H^o, S^o, and C _p ^o for the two dissociation processes have been derived and are compared with the corresponding values for tricine and the parent glycine in water and with those for other acids in 50 mass % methanol-water solvent. Both tricine and protonated tricine become weaker acids when methanol is added to the aqueous solvent. It appears that a strong stabilization of the zwitterion in water is responsible for this behavior. This conclusion is supported by comparing the changes in entropy and heat capacity for the dissociation of tricine with the values of these quantities for the dissociation of model acids of simple structure, such as ammonium ion and acetic acid.On leave 1971–1973 from Drury College, Springfield, Missouri     

Quantification of the inorganic phase of the pelagic aggregates from an iron contaminated lake by means of Raman spectroscopy

A semi-quantitative investigation of the inorganic phase of pelagic, iron-rich aggregates (iron snow, IS) formed in an iron polluted aquatic environment was performed by means of Raman spectroscopy. IS samples were collected from two basins of an acidic lignite mine lake and at two different water depths. Although the water chemistry differed at all four sites with respect to oxygen, pH, and, Fe(II) concentrations, the Raman analyses showed that the main mineral formed was schwertmannite (ideal formula: Fe₈O₈(OH)₆SO₄) with concentrations of more than 88% in all IS samples. To determine potential differences in the microbial communities of the IS samples we used denaturing gradient gel electrophoresis. Microbial communities differed between two basins, but showed similarities between redoxcline and deeper water layers of IS samples from the same basin. Surprisingly, these microbiological differences did not lead to strikingly qualitative similarities in the mineral composition, although the initial step in mineral formation, the oxidation of Fe(II) to Fe(III), is a pure microbial process at low pH. Thus, a semi-quantitative method was necessary to elucidate differences in the consecutive mineralization process which is apparently more controlled by water geochemical conditions.     

Nature of the Ftir Band in Acidic Zeolites

The nature of a FTIR band (1490 cm ^-1 ) in the spectrum of zeolite HZSM-5 after pyridine adsorption was investigated. It is shown that the source of this band is not a combined contribution from Brönsted and Lewis acidic sites as widely believed.     

Computational modelling of variably saturated flow in porous media with complex three‐dimensional geometries

A computational procedure is presented for solving complex variably saturated flows in porous media, that may easily be implemented into existing conventional finite‐volume‐based computational fluid dynamics codes, so that their functionality might be geared upon to readily enable the modelling of a complex suite of interacting fluid, thermal and chemical reaction process physics. This procedure has been integrated within a multi‐physics finite volume unstructured mesh framework, allowing arbitrarily complex three‐dimensional geometries to be modelled. The model is particularly targeted at ore heap‐leaching processes, which encounter complex flow problems, such as infiltration into dry soil, drainage, perched water tables and flow through heterogeneous materials, but is equally applicable to any process involving flow through porous media, such as in environmental recovery processes. The computational procedure is based on the mixed form of the classical Richards equation, employing an adaptive transformed mixed algorithm that is numerically robust and significantly reduces compute (or CPU) time. The computational procedure is accurate (compares well with other methods and analytical data), comprehensive (representing any kind of porous flow model), and is computationally efficient. As such, this procedure provides a suitable basis for the implementation of large‐scale industrial heap‐leach models. Copyright © 2005 John Wiley & Sons, Ltd.     

A green and fast chromatographic method for determining organic compound mobility in soils

Soil leaching column chromatography (SLCC) employing totally aqueous mobile phases has been used for the estimation of retardation factors (R) of heterocyclic compounds and heteroatom-substituted aryl derivatives Aniline, Aniside, Cresol, Hydroquinone, p-Nitroaniline, Phenol, Phenylenediamine, Piridine, Sulfanilamide, Sulfathiazole, Sulfamethoxazole, Metolachlor and Toluene in soils with low fraction of organic carbon. Small columns (0.39 cm × 10 cm i.d.) were packed with soils of different compositions (alluvial sediment, coarse sand and standard Eurosoil4 mixed with quartz). The theory of linear chromatography was employed to correlate statistical peak moments to R. Rs estimated through SLCC were compared with those derived from water–organic carbon partitioning coefficient reported in the literature. The adsorption isotherm of Metolachlor was measured by frontal analysis on a small column packed with alluvial sediment. The approach proposed for measuring the adsorption isotherm requires small amounts of chemicals and soils and does not need fraction collection nor detector calibration. The information obtained by SLCC experiments was used to predict the elution of Metolachlor and Phenol on a large column (8.9 cm × 100 cm i.d.) packed with alluvial sediment. The method used in this work, not making use of any chemical solvents, respects the fundamental concepts of green chemistry.     

制备条件对Raney铁结构与性能的影响

描述新型Ｒａｎｅｙ铁催化剂在制备时的抽滤工艺、抽滤温度、碱液浓度及合金组成等因素对其结构参数和浆态相Ｆ－Ｔ合成反应性能的影响规律，得到了较优化的催化剂制备参数；采用常规的制备途径，合金铝铁比为４，抽滤温度为８５℃，碱液浓度为２５％ＮａＯＨ所制备的Ｒａｎｅｙ铁催化剂Ｆ－Ｔ活性可以达到催化剂的水平。     

银杏叶黄酮类化合物的提取分离Ⅰ.银杏黄酮化合物的提取

银杏叶为银杏科银杏属植物银杏（Ginkgo biloba L.)的叶子,银杏在植物学和化学上占有重要地位。据《本草纲目》记载,银杏果具有敛肺平喘,止遗尿,白带作用,近年来,国内外学者对银杏提取物（GBE）进行了大量的研究,发现其主要药用成分之一为黄酮类化合物,以银杏 叶为原料提取制成的药物,用于对心血管,脑血管,动脉硬化,高血压等疾病的治疗,有其他药物不能达到的特殊疗效^[1-4]。另外,银杏制剂长期服用几乎没有毒副作用,银杏叶制品还可用于生物农药,保健食品,化妆品等方面,如何从银杏叶中提取有效成分有研究的关键。银杏叶黄酮化合物的提取包括银杏叶黄酮化合物的浸取和浸出液的富集分离两大部分。本文主要讨论银杏叶黄酮类化合物的浸取。