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.     

Sorption of radionuclides on inorganic sorbents

Inorganic sorbents are often used in separation of metals and radionuclides in radioanalytical application and they were also used in technological scale for separation of radionuclides in cleanup of Three Mile Island NPP. Inorganic sorbents become popular in the last years because no problem with organic contamination, there are stable against radiation, sorption efficiency can be tailor made for selective separation of chosen metal. Contrary to the organic sorbents they have usually lower capacity and chemical stability is limited to narrower pH. Nevertheless of some problems, many good properties of inorganic sorbents make them very attractive for sorption study.     

Sorption of methylxanthines by different sorbents

Sorption of caffeine, theophylline, theobromine, diprophylline, and pentoxyphylline on different sorbents (supercross-linked polystyrene, surface-modified copolymer of styrene and divinylbenzene Strata-X, and carbon nanomaterials Taunit and Diasorb-100-C₁₆T) was studied in a static mode in an effort to find new sorbents suitable for sorption isolation and concentration of methylxanthines. The peculiarities of sorption of methylxanthines were explained in relation to the solution acidity, the nature of the sorbates and their concentration, the nature of the solvent, and the structural characteristics of the sorbents.     

Sorption of organic dyes of various molecular weights on mineral sorbents and on sea and lake bottom sediments

The sorption of organic dyes of various molecular weights (from 100 to 700 amu) from aqueous solutions on minerals and on sea and lake bottom sediments was studied.     

Sorption of cesium on composite sorbents based on nickel ferrocyanide

Composite sorbents based on potassium nickel ferrocyanide embedded in silica gel matrix were prepared and characterised by powdered X-ray diffraction analysis, IR spectra, Mössbauer spectra and electron microscopy. The sorbent exhibits very good efficiency for cesium uptake and radiation resistance. The sorption capacity for cesium ions is comparable with the capacity for the pure ferrocyanides.     

Sorption characteristics ofN-alkylimidazoles under conditions of capillary chromatography

The retention indices forN-n-alkyl (C₁-C₅) substituted imidazoles with Me, Et, Pr, and Bu groups in different positions of the cycle were determined. Two capillary columns with OV-101/KF and PEG-40M/KF were used. The two nitrogen atoms of the imidazole molecule were shown to have different effects on the contributions of the alkyl groups to the retention indices. The maximum and minimum contributions are observed for the substituents at the 5 and 4 positions of the imidazole cycle, respectively. An increase in a size of the C _m H_2m+1 substituent attached to the N(1) atom has a notable effect only on the contributions of the alkyl groups at the 2 and 5 positions. The retention indices values for a homologous series with ann-alkyl group attached to the N or C(2) atom were described by a universal type equation. The obtained equations can be used for predicting the retention indices of new homologs and identification ofN-alkylimidazoles in complex mixtures.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 309–313, February, 1995.     

Sorption and kinetic properties of radiocesium-selective organomineral sorbents

Comparative analysis of the sorption and kinetic properties was carried out for organomineral sorbents synthesized by two routes: (1) from an organomineral suspension and (2) from aqueous-organic solutions.     

Sorption of benzotriazoles under the conditions of RP HPLC

The results of a chromatographic study of sorption of several benzotriazole derivatives on octadecyl silica gel were reported. The physicochemical and electronic parameters of benzotriazoles were calculated. The effect of the structure of analyte molecules and eluent composition on chromatographic retention of these substances was analyzed.     

Sorption of chromium(VI) on ion-exchange resins and sorbents

Sorption of Cr(VI) on AV-17 and EDE-10P anion exchangers, KU-2 and KB-4 cation exchangers, activated charcoal, and foamed graphite (STRG) is studied.     

常温常压下β沸石改性吸附剂脱除噻吩类硫的研究

在合成不同硅铝比Naβ沸石的基础上,采用固相离子交换方法制备了Cu(I)、Ag(I)离子改性的β沸石系列吸附剂。样品的结晶度和BET比表面积有所降低,XRD表征结果表明,所制备的样品保持了结构的完整性,随着硅铝比的增加,Naβ样品的BET比表面积增加。Cu(I)、Ag(I)离子的引入使样品的红外骨架振动峰向低波数移动,与相同硅铝比的Naβ沸石相比,吸附剂的BET比表面积有所降低。对模型油的静态吸附结果表明,硅铝摩尔比为25时Cu(I)β吸附性能最好,模型油中硫的质量分数降到10×10－6以下,脱除率达到95％,Ag(I)β次之,脱除率达到87％。常温常压下固定床动态吸附穿透实验得到Cu(I)β、Ag(I)β的穿透硫容分别为0.144mmol/g和0.132mmol/g。     

Sorption of catechins under conditions of reverse-phase high-efficiency liquid chromatography

The physico-chemical principles of catechin sorption from various polar solvents onto silica gel modified with octadecyl groups were studied. Thermodynamic characteristics of the sorption were calculated, and the applicability of different models of retention was demonstrated for catechins under the conditions of reverse-phase high-efficiency liquid chromatography.     

Sorption of arsenic onto inorganic sorbents modified with iron compounds

Granulated inorganic sorbents based on silica gel of KSKG grade and aluminum oxide and modified with Fe(III) compounds were developed for water treatment to remove As(V). The influence of the particle size of the modifying additive on the ability of silica gel to take up As(V) was examined. The KSKG-based sorbents modified with nanoparticles of Fe(III) compounds exhibit the highest sorption capacity. The capacity of silica gel based sorbents modified with nanoparticles of iron compounds for As(V) is higher than that of analogous sorbents modified with iron oxides prepared by thermal decomposition of Fe(III) nitrate.     

Sorption of strontium by sorbents on the base of di-(tert-butylcyclohexano)-18-crown-6 with use of various diluents

Journal of Radioanalytical and Nuclear Chemistry - Set of sorbents were obtained on the base of di-(tert-butylcyclohexano)-18-crown-6, various diluents and styrene–divinylbenzene support for...     

Comparative study of breakthrough volumes BTV on various sorbents

Summary Breakthrough volumes on ten sorbents (Chromosorb 102, 104, 105 and 106, Porapak R and S, XAD-2, XAD-7, Tenax GC and Carbosphere) have been determined for vapours of 15 volatile organic compounds (halogenated hydrocarbons, alcohols, etc.). The volumes were determined by an indirect method employing typical chromatographic parameters such as retention volume and peak width.The method seems to be useful for preliminary estimation of adsorption capacity of various sorbents. It is not suitable, however, for the investigation of the effect of various parameters on the breakthrough volume.

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Vergleichende Untersuchung des Durchbruchsvolumens an verschiedenen Sorbentien

Zusammenfassung An 10 verschiedenen Sorbentien (Chromosorb 102, 104, 105, 106; Porapak R und S; XAD-2; XAD-7; Tenax GC; Carbosphere) wurden für 15 flüchtige organische Verbindungen (halogenierte Kohlenwasserstoffe, Alkohole u. a.) die Durchbruchsvolumina bestimmt. Es wurde dafür ein indirektes Verfahren mit typischen chromatographischen Parametern (Retentionsvolumen, Peakbreite) benutzt. Die Methode erscheint nützlich für die vorläufige Abschätzung der Adsorptionskapazität von Sorbentien, eignet sich jedoch nicht für die Untersuchung des Einflusses verschiedener Parameter auf das Durchbruchsvolumen.

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Part of this research was supported by Institute of Oceanology, Polish Academy of Sciences, Gdask, grant MR. I-15.     

Sorption of Quillaja saponaria Molina saponin with chitosan under equilibrium conditions

Russian Journal of General Chemistry - Equilibrium sorption of saponin from Quillaja saponaria Molina with chitosan has been analyzed. The shape of the sorption isotherm is determined by the...     

Transesterification over various zeolites under liquid-phase conditions

Transesterification of β-keto esters with a variety of alcohols to the corresponding β-keto esters has been carried out efficiently over aluminosilicates simply by refluxing in toluene under liquid-phase conditions. Aliphatic β-keto esters exhibit the higher reactivity than the aromatic and/or cyclic β-keto esters, whereas other esters such as -keto esters, ,β-unsaturated esters, normal esters, and -halo esters fail to undergo the transesterification. The reaction proceeds smoothly with primary alcohols than the tertiary-, cyclic-, and allylic alcohols. The large-pore zeolites such as Y, mordenite, and β show higher activity than the medium-pore ZSM-5 and the partial removal of framework aluminum from the large-pore zeolites by dealumination increases their activity. The aluminum containing mesoporous MCM-41 shows poor activity. Among the different solvents used toluene leads to the highest activity and the optimum catalyst concentration found was ca. 20 wt.% of the substrate. The activity increases with increasing reaction temperature. The reaction pathway consists of formation of acyl ketene intermediate by the interaction of β-keto esters with Brønsted acid sites of the catalyst, followed by nucleophilic attack of the alcohol at the electrophilic center and successive elimination of the proton to give the product.     

Behaviour of protein-stabilised emulsions under various physiological conditions

Emulsion forms a major part of many processed food formulations. During the past few decades, the physico-chemical properties of oil-in-water emulsions under various food processing conditions have been extensively studied. However, over the recent years, interest has turned to understanding the behaviour of emulsions during consumption, i.e. physiological processing. In general, on ingestion, an emulsion is exposed to a relatively narrow range of physical (e.g. shear and temperature) and biochemical (e.g. dilution, pH, pepsin, pancreatin, mucins and bile salts) environments as it passes through the mouth into the stomach and then the intestines. There is currently limited knowledge of the physico-chemical and structural changes, which an emulsion may undergo when it passes through the physiologically active regime. A better understanding of the gastro-intestinal processing of emulsions would allow manipulation of physico-chemical and interfacial properties to modulate lipid ingestion, improve bioavailability of lipid soluble nutrients and reduce absorption of saturated fats, cholesterol and trans fats.Food emulsions are commonly stabilised by proteins, as they are not only excellent emulsifiers but also provide nutritional benefits to the product. The effects of digestion conditions on interfacial protein structures are complicated because of potential breakdown of these structures by proteolytic enzymes of the gastrointestinal tract. Studies dealing directly with the behaviour of protein-based emulsions under digestion conditions are very limited. This paper provides an overview of the behaviour of oil-in-water emulsions stabilised with globular proteins, namely lactoferrin and β-lactoglobulin. Recent advances in understanding the interactions between interfacial proteins on oil droplets and various physiological materials (e.g. enzymes and bile salts) in in vitro digestion systems are considered. Major emphasis is placed on the recent work carried out in our laboratory at Massey University on the behaviour of milk protein based emulsions (lactoferrin or β-lactoglobulin) during their passage through the gastro-intestinal tract.     

Thermal inactivation of alkali phosphatases under various conditions

The thermal inactivation of alkali phosphatases from bacteria Escherichia coli (ECAP), bovine intestines (bovine IAP), and chicken intestines (chicken IAP) was studied in different buffer solutions and in the solid state. The conclusion was made that these enzymes had maximum stability in the solid state, and, in a carbonate buffer solution, their activity decreased most rapidly. It was found that the bacterial enzyme was more stable than animal phosphatases. It was noted that, for ECAP, four intermediate stages preceded the loss of enzyme activity, and, for bovine and chicken IAPs, three intermediate stages were observed. The activation energy of thermal inactivation of ECAP over the range 25–70°C was determined to be 80 kJ/mol; it corresponded to the dissociation of active dimers into inactive monomers. Higher activation energies (∼200 kJ/mol) observed at the initial stage of thermal inactivation of animal phosphatases resulted from the simultaneous loss of enzyme activity caused by dimer dissociation and denaturation. It was shown that the activation energy of denaturation of monomeric animal alkali phosphatases ranged from 330 to 380 kJ/mol depending on buffer media. It was concluded that the inactivation of solid samples of alkali phosphatases at 95°C was accompanied by an about twofold decrease in the content of β structures in protein molecules. Original Russian Text ? L.F. Atyaksheva, B.N. Tarasevich, E.S. Chukhrai, O.M. Poltorak, 2009, published in Zhurnal Fizicheskoi Khimii, 2009, Vol. 83, No. 2, pp. 391–396.