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  • Author or Editor: S. M. Aly x
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Abstract  

The solid-state thermal reactions of 2,6-diamino-4-chloropyrimidine, 3,3-dimethoxybenzidine and of thiosemicarbazide with each of 2-hydroxy-1-naphthaldehyde and 2,4-dihydroxybenzaldehyde in a mole ratio of 1∶1 produced (1+1) condensation products (‘half units’). These solid state reactions have been studied by means of differential thermal analysis (DTA). The products of the reactions were identified using elemental analysis and IR spectroscopy. Some kinetic parameters such as orders and activation energies of the reactions were evaluated form the DTA curves.

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Summary  

Many studies have shown that water hyacinth (Eichhornia crassipes) roots can be used to accumulate high concentrations of organic as well as inorganic pollutants. They are currently used to remediate aquatic environments and aqueous solutions. In the present study, sorption of uranium from aqueous solutions by using dried roots of water hyacinth has been investigated. The sorption of uranium was examined as a function of initial concentration, pH, weight of roots and contact time. Five different concentrations 20, 40, 60, 80, and 100 μg . ml-1 were used. Sorption proves to be very rapid and depend on pH, weight of roots and concentration of uranium. Maximum sorption capacity of water hyacinth roots was 64,000 U6+ μg/g. The sorption of uranium by water hyacinth roots follows a Langmuir isotherm.

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Abstract  

Synergic extraction of trivalent iron and cobalt with thenoyltriflouroacetone (HTTA) and the synergic bases (B) benzylamine (BA), dibenzylamine (DBA) and tribenzylamine (TBA) was studied. The extracted adducts proved to have the general formula M(TTA)3·B for all the amines investigated. The formation constants of the mixed-ligand complexes decrease in the order DBA>TBA>BA. While equilibrium constant β3,1 for the Co(TTA)3·DBA complex is higher than the corresponding iron adduct, β3,1 for the iron adducts with BA and TBA are higher than those for cobalt.

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Abstract  

The effect of ten pure diluents and different mixtures of nitrobenzene and toluene on the synergic extraction of Co2+ by the thenoyltrifluoroacetone (HTTA)-tribenzylamine (TBA) mixture is studied. The logarithm of the extraction constant of Co(TTA)2 increases with increasing dielectric constant of the diluent, whereas the logarithm of the formation constant of the extracted adduct Co(TTA)2TBA decreases with increasing dielectric constant of the diluent. This behaviour is explained by changes in the hydrophobic character of the extracted species. The theory of regular solutions is successfully applied to the extracted adduct. Consideration of the self-association of the amine salt is necessary in the treatment of the equilibria involved.

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Abstract  

Chromatographic column investigations were performed for the recovery of uranium from aqueous medium of pH 1.0 and ionic strength of 0.6M/NaNO3/, which is comparable /in its chemical activity/ to certain high active waste solutions. Six different active beds were tested and compared in terms of their capacity for uranium, height equivalent to theoretical plate and their numbers. The main uranium species present in the medium were elucidated.

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Abstract  

The effect of temperature on the extraction of Co2+, Zn2+, Cd1+ and Hg2+ by salicylaldoxime diluted with carbon tetrachloride was investigated radiometrically. It is found that the extraction constants at 25°C increase linearly with l/r, where r is the effective coordination radius of the metal cation. The thermodynamic data calculated from the effect of temperature on the extraction showed that, 1) the extraction process is endothermic, 2) the dehydration of the metal cation in the extraction process is the predominating factor in determining the enthalpy variation and 3) the entropy variation is a contribution of the degree of order caused by the hydration of the proton and the highly ordered chelate structure of the extracted species.

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Abstract  

The solvent extraction of divalent iron, cobalt, copper and zinc from perchlorate medium of constant ionic strength (0.1 H+, NaClO4) into a mixture of thenoyltrifluoroacetone (HTTA) and dibenzylamine (DBA) in chloroform has been studied. The extraction of the different cations were found to increase by more than 103 order of magnitude in presence of DBA. Slope analysis of the extraction results assumed a general formula of M(TTA)2·DBA for the extractable adduct. A stability order of Fe(TTA)2·DBA>Co(TTA)2 ·DBA>Zn(TTA)2·DBA>Cu(TTA)2·DBA has been decumented.

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The toxicity of Melissa officinalis L. essential oil and its formulation (Melissacide) were evaluated against eggs and females of two predatory phytoseiid mites, Typhlodromips swirskii (Athias Henriot) and Neoseiulus barkeri (Hughes), using direct spray. Results indicate that both tested materials were potent on predatory females than egg stage. Typhlodromips swirskii was proved to be more sensitive to the oil and formulation than N. barkeri.

Females mortality were (62-100%) in T. swirskii, and (46-69%) in N. barkeri, when both predatory mites were sprayed with LC50 and LC90 of the oil and Melissacide reported on Tetranychus urticae Koch. Females of both predators were suffered from reduction in food consumption when sprayed with two sublethal concentrations of Melissacide, while insignificant differences reported in daily number of eggs deposited by females of T. swirskii, when sprayed with its LC25 value of Melissacide and control.

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Seed-bone infection level of watermelon with F. oxysporum f. sp. niveum has a significant effect on wilt incidence. When high (23-31.5%) or mo­de­­rate (8.5-9.5%) seed-borne infection occurred, wilt incidence reached up to 47.5-57.5% and 45-55%, respectively. However, when low (1.5-2.5%) seed borne levels occurred wilt incidence did not increase more than 5-10%. It is recommended to use seeds of free or low infection levels of Fusarium to minimize watermelon wilt incidence.

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The thermal decompositions of nine mixed ligand complexes of Mn(II) containing picrate and mono- or bidentate nitrogen ligands were studied by thermogravimetry. The kinetics of decomposition were examined by using the Coats-Redfern and Horowitz-Metzger equations; the decomposition was in all cases of the first order. The activation energies and other kinetic parameters were computed. The decomposition mechanisms exhibited a similar character for all the studied compounds. It was observed from the TG curves that the complexes decomposed to give six-coordinate intermediates, formed from substitution of the picrate into the inner coordination sphere. These intermediates decomposed to Mn(II) picrate and finally to Mn2O3.

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