X射线荧光光谱法测定石灰岩和白云岩中主次量组分

建立用X射线荧光光谱法同时测定石灰岩和白云岩中主次量组分(CaO、MgO、Al2 O3、SiO2、Fe2O3、TiO2、K2O、Na2O、MnO、P2O5)的快速分析方法,在优化条件下,采用国家标准样品建立的标准工作曲线和基体校准一体回归方程进行谱线重叠干扰和基体效应校正.实验结果表明,各元素的检出限在80～280μg...     

Solid-gas reactions: Study of sulphation of limestone using thermogravimetry

Comparative data are presented on the absorption rate and capacity for SO₂ capture by a natural Polish limestone with and without sodium chloride additive. Two sets of experiments were carried out, under dry and wet conditions during limestone calcination and sulphation.The presence of water vapour brought about a higher reactivity of the sorbent, probably as a result of an effect on the sintering of lime and through the influence of the CaSO₄ layer. Further morphological investigations could provide confirmation of the present hypothesis.

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Zusammenfassung Absorptionsgeschwindigkeit und -kapazität für SO₂ an einem polnischen Kalkstein mit oder ohne NaCl-Zusatz werden verglichen. Zwei Reihen von Experimenten wurden in trockener bzw. wasserdampfhaltiger Atmosphäre bei der Calcination und Sulfatbildung durchgeführt. In Gegenwart von Wasserdampf wird die Reaktivität des Absorbens infolge Sinterung des Kalks und trotz des Einflusses der CaSO₄-Schicht erhöht. Künftige morphologische Untersuchungen sollen diese Hypothese eventuel bestätigen.

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The author would like to thank Prof. E. M. Bulewicz of this Institute for valuable discussions, and Mr. W. Balcerowiak for making available the facilities of the Laboratory of the Institute of Heavy Organic Synthesis in Kdzierzyn-Kole.     

Analysis of isothermal kinetic data from solid-state reactions

In most solid state reactions the reaction velocity can be described as a product of two functionsK(T) andf(1?α) whereT is the temperature and α the degree of conversion of the solid reactant. The physical interpretation of these functions is discussed, and a systematic method is described by whichf(1?α) of a reaction is identified from its kinetic data.K(T) and the reaction mechanism are then determined. This method has been successfully applied to analyse the kinetics of the thermal decomposition of silver azide.     

Multifunctional sorbents for the extraction of pesticide multiresidues from natural waters

In this work multifunctional sorbents, based on surfactant-coated mineral oxides, are assessed for the simultaneous extraction/preconcentration of pesticide multiresidues from aqueous environmental samples. Seventeen pesticides, representative of all the common groups (triazines, phenylureas, carbamates, azols, anilides, chloroacetanilides, organophosphorous, phenoxyacids, aryloxy acids and phenols), are selected for this study. The sorbents assessed are pure sodium dodecyl sulphate (SDS) and mixed tetrabutylammonium (TBA)-SDS hemimicelles and/or admicelles adsorbed onto alumina. Because of their multifunctional character, these sorbents provide different retention mechanisms (i.e. hydrophobic, ionic and/or π-cation interactions), which highly contribute to the efficient retention of pesticides with different polarities and acidities (bases, neutrals and acids). In addition, the low volume of eluent required for complete elution of analytes (typically 1-2 mL) avoided the need of using time-consuming and tedious evaporation steps that generally are needed when cross-linked polymeric resins or carbon materials are used as sorbents. The performance of two sorbents, i.e. SDS and TBA-SDS mixed hemimicelles/admicelles, for the admicellar solid-phase extraction (ASPE) of pesticide multiresidue was comparatively investigated. The latter was selected on the basis of the higher breakthrough volumes permitted, the lower volume of eluent required and the higher sample and eluent flow rates allowed. The proposed ASPE/LC/UV approach provided detection limits lower than 100 ng L⁻¹ for the determination of the 17 pesticides tested. Recoveries from spiked (at the ng L⁻¹ level) river and underground water samples was quantitative for most of the pesticides tested.     

Sorption of technetium and rhenium on natural sorbents under aerobic conditions

The uptake of technetium on bentonite materials has been studied from the point of view of the characterization of long-term radioactive elements behavior in nuclear waste repository. It is generally known that bentonite materials show an excellent cation-exchange capacity and on the other hand a poor uptake of anions. The aim of our research has been to find out the conditions suitable for technetium sorption on selected bentonite under oxidizing conditions. The influence of the addition of different materials (e.g., activated carbon, graphite, Fe²⁺, Fe) with bentonite, the effect of solid:aqueous phase ratio and a pH value on the percentage of technetium uptake and on the K _d values were tested.This revised version was published online in November 2005 with corrections to the Cover Date.     

The graphical representation of equilibrium for the isothermal and isobaric reactions of ideal gases

The equilibrium for the isothermal and isobaric reactions of ideal gases is investigated in virtue of the intuitionistic figure. The curve is similar to the curve of tangential function which has one inflection and two vertical asymptotes. The equation only has one root ξ _e and it is suitable to find ξ _e by dichotomy. For non-inert substance, when or x_i^0 $$" align="middle" border="0"> , to increase substance i will make an equilibrium shift in the direction to deplete substance i; when {\nu_i} \mathord{\left/ {\vphantom {{\nu_i} {\sum_i {\nu _i}}}} \right. \kern-\nulldelimiterspace} {\sum _i {\nu _i}}> 0$$" align="middle" border="0"> , to increase substance i will make an equilibrium shift in the direction to produce more substance i.     

Redox reactions of natural alkaloid lappaconitine

A review on redox reactions of natural alkaloid lappaconitine, a known sodium channel blocker, is presented. The NMR and CIDNP data on the mechanism of phototransformation of lappaconitine, in particular, of its paramagnetic species formed by both the direct photolysis and photoinitiated interaction with electron donors and acceptors, are analyzed. Special attention is given to the interaction of lappaconitine with amino acids, which are present in the active site of the sodium channel. Hypotheses about a relationship between this process and the mechanism of therapeutic activity of lappaconitine are discussed. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 608–619, April, 2007.     

Uptake of plutonium from nuclear waste water by natural and chemically modified sorbents

The uptake of plutonium from model solution of boric acid labelled with²³⁹Pu by natural sorbents was studied. The range of pH of solution was from 5.1 to 8. For the uptake of Pu were used different natural and chemically modified natural sorbents of different mineralogical composition and from different deposits. The distribution coefficients for plutonium uptake were calculated and the best conditions for uptake were evaluated.     

Conditions for calibration of an isothermal titration calorimeter using chemical reactions

The reaction of protonation of 2-amino-2-(hydroxymethyl)-1,3-propanediol (TRIS) is a suitable one for the calibration of isothermal titration calorimeter (ITC), providing that experimental conditions are appropriately chosen. The conditions and methods for handling experimental data from a nanowatt-ITC are discussed. Also, the binding of Ba²⁺ to 18-Crown-6 is successfully used to check the accuracy and precision of the chemical calibration performed with TRIS. This latter reaction has the additional advantage that the data can also be used for a check on the determination of the value of a binding constant. The anomaly of the first injection in ITC is analyzed and, by combining calorimetric and spectroscopic measurements, it is shown that it mainly results from a backlash effect of the syringe plunger rather than from a diffusion effect.     

Studies on isothermal kinetics of some reactions of aluminum oxides and hydroxides

Thermal decomposition and hydrothermal reactions of aluminum oxides and hydroxides were studied. The starting material was gibbsite pretreated by grinding in different ways. Sixteen kinetic models were fitted and the rate constants were estimated at different temperatures. Mechanical activation of the starting gibbsite had an effect on the reactivity of samples in several subsequent reactions.A new quantity, the relative residual variance is defined for comparison of different linearized models, and it is proposed as a criterion of fit. This was applied in making statistics in order to find the well-fitting models.

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Zusammenfassung Es wurden die thermische Zersetzung und hydrothermische Reaktionen von Aluminiumoxiden und -hydroxiden untersucht. Das Ausgangsmaterial war Gibbsit, welches durch Zerkleinern auf verschiedene Weise vorbereitet wurde. Es wurden sechzehn kinetische Modelle angewendet und bei verschiedenen Temperaturen die Gesch-windigkeitskonstanten geschätzt. Die mechanische Aktivierung des Ausgangsmateriales Gibbsit beeinflu\t die Reaktivität der Proben in einigen Folgereaktionen.Für den Vergleich verschiedener Linearisationsmodelle wurde eine neue Grö\e, die relative Restvarianz definiert, die als Kriterium für die Anpassungsgüte vorgeschlagen wird. Dies wurde bei statistischen Untersuchungen angewendet, um die bestangepa\ten Modelle zu finden.

     

Influence of natural sorbents on the immobilization of spent ion exchange resins in cement

Summary Leach characteristics of ¹³⁷Cs and ⁶⁰Co radionuclides from spent mix bead ion exchange resins and both ordinary Portland cement and cement mixed with two kind of natural sorbents (bentonite and clinoptilolite) have been studied using the International Atomic Energy's (IAEA) standard leach method. The waste immobilization performance of low-level wastes in natural sorbent mixtures was determined. The solidification matrix was a standard Portland cement mixed with 290-350 (kg/m³) spent mix bead exchange resins, with or without 1-10% of bentonite or/and clinoptilolite. The leaching rates from the cement-bentonite matrix were measured after 300 days as ⁶⁰Co: (1.20-9.72) ^. 10^-5 cm/d and ¹³⁷Cs: (1.00-9.22) ^. 10^-4 cm/d. From the leaching data, the apparent diffusivity of cobalt and cesium in cement-bentonite or/and clinoptilolite matrix with a waste load of 350 kg/m³ of spent mix bead exchange resin was calculated as ⁶⁰Co: (1.0-5.9) ^. 10^-6 cm²/d and ¹³⁷Cs: (0.48-2.4) ^. 10^-4 cm²/d. The compressive strength of these samples is determined according to the ASTM standards.     

Non isothermal heat capacities and chemical reactions using a modulated DSC

An evaluation of measurements of heat capacities by modulated differential scanning calorimetry, MDSC is presented. Heat capacities were obtained from 130 to 550 K by a non isothermal technique in which a periodic modulation was added to the linear heating rate. Effects of amplitude and period of modulation, sample weight, sample type, pan type, and cell imbalance are described. Results are compared with those obtained using the isothermal technique. Heat capacity could be measured well into the decomposition region and separated from the non reversing signal due to chemical reaction (degradation), thus allowing a precise detection of onsets of the thermal degradation. This additional information will aid in the interpretation of the degradation chemistry, a field vital for the petroleum-industry.Dedicated to Professor Bernhard Wunderlich on the occasion of his 65th birthdayPart of this paper was presented at the 23rd Conference of the North American Thermal Analysis Society, Toronto, Canada, September 25–28, 1994.The author (MVN) acknowledges the experimental assistance provided by J. Balogh of Exxon Research and Engineering Company, Linden. Helpful discussions with A. Boller of the University of Tennessee at Knoxville, Dr. Y. Jin, General Electrical, and Dr. S. Sauerbrunn formerly of TA Instruments are also acknowledged.     

Comprehensive kinetic studies on isothermal and non-isothermal reactions of some aluminium compounds

Residual differences after model fitting were investigated in both isothermal and non-isothermal kinetics in order to make numerical comparisons between several models and various parameter-estimating methods. Data from two independent experimental series were evaluated. A large data set, collected earlier under isothermal conditions from decompositions and hydrothermal reactions of aluminium hydroxides and oxides, was processed first. It showed that mechanical activation of the starting gibbsite affected reactivity of samples in several subsequent reactions for all model equations tried. The relative residual deviation concept is introduced, and statistics were applied to find a model that fits a certain reaction in most of the cases. In the second study, the sulphate decomposition step of aluminium sulphate octadecahydrate was investigated. TG curves were measured using a constant heating rate. Dynamic models were fitted by three mathematical methods, including a new general purpose one. Fitting ability of the methods with various complexity were compared on the basis of residual deviations obtained after integration of the model equations. As well as evaluating the best fit, this new parameter-estimating method provides a statistical analysis of the reliability of the whole model fitting process.     

Sorption of metal cations on natural sorbents: Current state,problems and prospects

Data obtained in recent years that characterize the sorption capacity of natural sorbents with respect to the cations of a number of metals from nonexchangeable solutions and working fluids are generalized. We develop a technique for estimating the slip of pollutants with solutions in which the concentration of toxic cations does not exceed regulatory requirements. A method for calculating the kinetic curves of sorption is considered, which makes it possible to estimate the concentration of the pollutant coming out of the adsorber and the specific dynamic capacity of the sorbent to any current point of time from the beginning of the process.     

Reactivity of natural phenols in radical reactions

Activation enthalpies and energies and the rate constants of reactions with peroxyl, alkyl, and thiyl radicals (76 reactions) were calculated for a group of natural antioxidants (19 monohydroxy and polyhydroxy phenols). The calculation was performed with the use of the model of a radical abstraction reaction as the intersection of two parabolic potential curves. The results of the calculation were compared with experimental data: the average discrepancy in the activation energies of the reactions RO ₂ ^? + ArOH was 0.8 kJ/mol. Interatomic distances in the reaction centers of the transition states of the test reactions were calculated. Factors affecting the reactivity of these compounds are discussed.     

Carbon,natural and synthetic sorbents for decontamination of objects of ecosystems from pathogenic microflora

Physico-chemical characteristics and sorption activity of carbon, organosilica sorbents and their modified forms towards proteins, possessing specific activity, and cholerae vibrio have been studied. It was found, that carbon materials modified by copper (II) effectively extracts cholerae vibrio (100%) and may be recommended for disinfection of drinking water. Sorption capacity of organosilica sorbents and their modified by copper (II) forms towards pathogenic microflora (E.coli, St.aureus, Ps.aeruginosa) depending on the composition of the sorbents, concentration of the modified reagent, pH of medium have been evaluated. The rows of the increase of sorption of pathogenic microorganisms by synthetic sorbents in water-salt solutions were established: Al(III)<Zn(II)<Cu (II). It was shown that inhibiting effect of modified synthetic organosilica and natural sorbents towards such pathogenic microorganisms as E-coli, St.aureus Ps.aeruginosa and fungus Bacillus pyocyaneus accordingly is equal 80–98%.     

The multicomponent reactions and their libraries for natural and preparative chemistry

It was recently recognized that three different types of multi-component reactions (MCRs) exist. In preparative chemistry, the MCRs of type II form their products particularly efficiently. These reactions correspond to equilibria of educts and intermediate products, whose final products are formed practically irreversibly. In recent years, the four component reaction of the isocyanides (U-4CR) of type II and their unions with various reactions and MCRs have become an important industrial process for preparing products and their libraries. It has been demonstrated that all conceivable collections of U-4CR educts can be converted into the corresponding products. In the usual chemical reactions, only the substituents of the products can be varied, whereas the U-4CR and related reactions can also produce skeletally different types of products with diverse substituents. The preparative advantages of forming products by the one-pot MCRs and the great variety of the possible products are illustrated in this review.     

New correlations for the analysis of isothermal critical phenomena in heterogeneous catalytic reactions

Abstracr The kinetic hysteresis was analyzed for the simplest particular mechanism of a catalytic reaction exhibiting isothermal critical phenomena (the Langmuir-Hinshelwood mechanism). New correlations between the kinetic characteristics at the critical points of kinetic hysteresis were obtained.Hyprotech, 400, 119 14th Street, N.-W., Calgary, Alberta, T2N 1Z6, Canada.Kiev Polytechnical Institute of Ukraine. Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 32, No. 3, pp. 153–156, May–June, 1996. Original article submitted September 13, 1995.