Precipitation separation of lead and calcium,strontium, barium from acidic solutions using crown ether and tungstosilicic acid

It was found that lead reacts with 18-crown-6 (L) and tungstosilicic acid (H₄A) in acidic solutions and a compound with low solubility is formed what was confirmed by radiometric titration methods. Coprecipitation of complexion cation of PbL²⁺ with similar complexion cations of calcium, strontium and barium was studied. Formation of low soluble salts was utilized for separation of Pb from Ca, Sr and Ba from 1 mol·dm^–3 HNO₃. The ratio of Pb/Ca, Pb/Sr and Pb/Ba in the precipitation or separation factors S_pb/M undoubted depends on the ratio of the stability constants of lead and metals with 18C6 (_Pb/_M), what can be used for determination of more precise constant stability _M.     

Thermal decomposition of mineral zircon by alkali metal hydroxides

Thermal decomposition of zircon mineral was studied in the presence of sodium and potassium hydroxides and in the presence of a waste mixture of hydroxides containing NaOH and KOH in a weight ratio of 23. The process was controlled in such a way that the decomposition products might contain the minimum possible amount of alkali and could thus be applied for the syntheses of zircon pigments without any further exacting treatment.

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Zusammenfassung Es wurde die thermische Zersetzung eines Zirkonminerals in Gegenwart von Natrium- und Kaliumhydroxid-sowie in Gegenwart einer Altlauge mit einem Gehalt an NaOH und KOH im Verhältnis zwei zu drei untersucht. Der Prozeß wird derart gesteuert, daß die Zersetzungsprodukte einen möglichst geringen Anteil an Lauge besitzen und so ohne weitere arbeitsaufwändige Behandlungen zur Synthese von Zirkonpigmenten verwendet werden können.

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, 23. , , , - .

     

Sulfide ion electrooxidation catalysed by cobalt phthalocyanine microcrystals

Electrooxidation of sulfide ion catalysed by microcrystals of cobalt phthalocyanine was investigated by cyclic voltammetry in 0.5M KNO₃ at pH 9.22. Traces of catalyst were immobilized at the surface of a paraffin-impregnated graphite electrode by the mechanical transfer of its powder. The electro-oxidation of HS^– proceeds in two irreversible steps, with the first peak between 0 V and –0.12 V and the second at 0.17 V. The first step is second order in HS^– and its product is the adsorbed disulfide, which may further dissociate to give adsorbed sulfur atoms. The reduction of sulfur occurs at –0.1 V.     

Exciton absorption spectra of optically excited linear molecular aggregates

Exciton absorption spectrum of optically excited linear molecular aggregate is theoretically investigated. The sum rules for the integral intensity of the absorption spectrum are derived. The dipole moments of the optical transitions from the one-exciton states to the two-exciton states are presented. The results obtained indicate an energy increase of the exciton transition after a single excitation of the aggregate. It accounts for the observed short-wavelength shift of the J-band of the pseudoisocyanine (PIC) J-aggregates after their optical excitation. The comparison of the experimental energy of the shift with its theoretical evaluation allows to estimate the number of monomers forming a typical PIC J-aggregate in the solutionN ?20–30.     

Photocatalytic TiO2 Coatings: Effect of Substrate and Template

Summary. Transparent TiO₂ films with a high photodegradation activity towards an azo dye in aqueous solution were prepared by sol–gel processing. Films on soda–lime glass supports protected with a thin silica barrier layer exhibited better crystallization and monodisperse nanoparticles, higher absorption of light below 370 nm, and higher photocatalytic activity than those films deposited on bare glass supports proving the detrimental effect of interdiffused sodium ions on the development of the anatase nanostructure. The effect of substrate was more pronounced in thinner films (300 nm) than in thicker ones (1200 nm), which were achieved by adding a template (i.e. Pluronic F127) to the sol.     

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.     

Correlation between Lipophilicity of the Ligands and the Hepatobiliary Properties of the Radiopharmaceuticals: Approach to the Development of New IDA Derivatives

The partition coefficient (log P) for n-octanol/water system was calculated applying PACO program for various theoretically possible mono and dihalogenated IDA derivatives. Some of the synthesized ligands (SOLCOIODIDA, IODIDA and DIIODIDA) were labeled with the technetium-99m. The biodistribution and influence of bilirubin on their biokinetics were investigated in rats. The correlation between partition coefficients of ligands increase (log P) and better hepatobiliary properties of ^99mTc-IDA derivatives was determined. The values of log P increase from 1.16 for SOLCOIODIDA, 3.11 for IODIDA to 3.47 for DIIODIDA. In correlation with these results, biliary excretion decreased for 59% for ^99mTc-SOLCOIODIDA and 11% for ^99mTc-IODIDA and ^99mTc-DIIODIDA under hyperbilirubinemia (3.5 min after injection) and 45%, 11% and 0.38% respectively (15 min after injection). The highest biliary excretion had ^99mTc-DIIODIDA (55.4% for 3.5 min). Considering the correlation between hepatobiliary properties and log P, the evaluation of biological properties for various trifluoromethyl mono and dihalogenated IDA derivatives was performed on the basis of the calculated log P in order to synthetize a new radiopharmaceutical for hepatobiliary scintigraphy.     

Liquid chromatography of benzene derivatives on a porous methacrylate copolymer containing epoxy groups

Summary The retention of benzene derivatives with nonpolar and polar substituents on a porous methacrylate copolymer containing epoxy groups using both nonpolar and polar eluents was investigated. When n-hexane is used as the eluent, the retention of n-alkylbenzenes and polymethylbenzenes is weaker than that of benzene. In the case of benzene derivatives containing polar functional groups their capacity ratios (k) on this porous polymer increases approximately linearly with the increase of the adsorbate molecules dipole moment. The retention characteristics of the methacrylate copolymer were compared with that of a styrene-divinylbenzene copolymer and silica gels with a hydroxylated surface and with a surface modified by chemically bonded alkylsilyl groups.     

Influence of the pyridine methyl substituent position on the chemical changes of the NCS groups in the thermal decomposition of coordination compounds of the type Cu(NCS)2L2

The influence of the position of the CH₃ group in picoline and lutidine ligands on the degree of chemical change of the NCS groups in coordination compounds of the type Cu(NCS)₂L₂ (whereL=2-, 3- and 4-picoline, and 2,3-, 2,4-, 2,5-, 2,6-, 3,4- and 3,5-lutidine) is dealt with. The most marked effect of the CH₃ group is found to be exerted in position 4. This effect of the methyl group on the degree of chemical change points to the mutual influence of the ligands in coordination compounds of Cu(II).

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Zusammenfassung Der Artikel befaßt sich mit dem Einfluß der Lage der CH₃ Gruppe in Pikolinen und Lutidinen als Liganden auf den Grad der chemischen Änderungen der Gruppen NSC in Koordinationsverbindungen des Typs Cu(NCS)₂L₂ (L=2-, 3- und 4-Pikoline, 2,3-, 2,4-, 2,5-, 2,6-, 3,4- und 3,5-Lutidine). Der ausgeprägteste Effekt der CH₃ Gruppe wurde in der Position 4 beobachtet. Dieser Einfluß der Methylgruppe auf das Ausmaß der chemischen Änderungen deutet auch auf die gegenseitige Wirkung der Liganden in Koordinationsverbindungen von Cu(II).

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Résumé L'article a trait à l'influence de la position du groupe CH₂ dans les picolines et lutidines, en tant que ligands, sur le degré des changements chimiques des groupes SCN dans les composés de coordination du type Cu(SCN)₂L₂ (L=2-, 3 et 4-picoline, 2,3-, 2,4-,2,5-, 2,6-, 3,4- et 3,6-lutidine). L'effet le plus prononcé du groupe CH₃ s'observe en position 4. Cette influence du groupe méthyle sur le degré des changements chimiques indique aussi l'influence mutuelle des ligands dans les composés de coordination du Cu(II).

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- , , NCS Cu(NCS)₂,L₂, L=2-, 3- 4- , 2.3-, 2.4-, 2.5-, 2.6-, 3.4- 3.5-. , 4. Cu(II).

     

Pulse plating effect on microstructure and corrosion properties of Zn–Ni alloy coatings

The influence of pulse plating parameters on the surface morphology, grain size, lattice imperfection and corrosion properties of Zn–Ni alloy has been studied. The coatings were electrodeposited in an alkaline cyanide-free solution. AFM was applied for surface morphology examination, XRD measurements were carried out for phase composition and texture analysis, electron probe microanalysis was used for alloy chemical composition studies, while electrochemical techniques were applied for corrosion performance evaluation. The pulse plated Zn–Ni coatings appeared to consist of the γ-Zn₂₁Ni₅ phase and the composition of the alloy depended on the plating parameters. The grain size, lattice imperfection and homogeneity of grain distribution were established to be the main factors determining corrosion behaviour of the coating. Presented at the 4th Baltic Conference on Electrochemistry, Greifswald, March 13–16, 2005