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Abstract : UV-vis Investigation of β-Carotene in Presence of AOT/n-Heptane, Cyclohexane, Tetrahydrofuran/Water System
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Abstract: The precise measurements of β–carotene absorbance in presence of AOT/solvent/water systems at 25oC by UV-vis technique are reported. The solvents selected were: n-heptane, cyclohexane, and tetrahydrofuran. The concentrations of AOT [Aerosol-OT (sodium bis(2-ethylhexyl) sulfosuccinate)] were varied from 0.01 to 0.2mol/kg. β–carotene concentration in quvette during UV-vis spectrum registration was not the same in each solvents because of different absorption intensity depending on the solvent. Water concentration in the studied systems was defined by R parameter according to relation: R=[H2O]/[AOT] and was equal 0; 5; 10 both in n-heptane and cyclohexane, and 0; 10 and 20 in tetrahydrofuran. Obtained results showed a noticeable decreasing of β–carotene absorbance as a function of AOT concentration. There is evidenced red shift of β–carotene absorbance depending on the solvent in the following order: tetrahydrofuran >cyclohexane>n-heptane. Presented results show that β–carotene absorbance decreased with water concentration in the system. It had been happened because the water molecules located in the core of micelles make its curvature bigger and the hydrocarbon chains forming palisade layer in AOT reversed micelles get more space. As a consequence β–carotene molecules penetrated this layer dipper comparing to systems without water. Keywords: β–carotene, AOT, n-heptane, cyclohexane , tetrahydrofuran, UV-vis.Download Full Article |
Abstract : Amidoalkyl Naphthols: Trifluoroacetic Acid (TFA) Catalyzed One-Pot, Multi-Component Synthesis
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Abstract: Trifluoroacetic acid (TFA) was found as an efficient catalyst for the synthesis of amidoalkyl naphthols from aromatic aldehydes, β-naphthol and acetamide/benzamide under solvent free condition at 80o C. All the synthesized compounds were characterized by IR, 1H NMR and Mass spectra. The advantages of the new method were good yields, short reaction times, simple work-up, inexpensive and easily available catalyst and economical due to absence of solvent. Therefore, this method could be an attractive alternative to existing methods for the synthesis of biologically important amidoalkyl naphthols. Keywords: Amidoalkyl naphthols, multicomponent reaction, solvent-free conditions, trifluoroacetic acid.Download Full Article |
Abstract : The Regularities of Electrolytic Dissociation of Weak Dibasic and Tribasic Organic Wine Acids
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Abstract: The weak dibasic and tribasic organic acids in wine: tartaric, malic, citric and succinic acids are the important components having direct influence on various properties of wine. The regularities of electrolytic dissociation of these acids determine all their useful properties. With the aid of suggested by authors original method for analysis the complex equilibria of the processes of dissociation of weak multibasic organic acids the main dissociation parameters of tartaric, malic, citric and succinic acids in their dilute solutions: the values of usual and “partial” degrees of dissociation of all steps, the concentrations of all anions, hydrogen ions and undissociated acid molecules are determined. The concentration intervals of predominance of various charged and uncharged substances in dilute solutions of all above mentioned acids are also determined. The simple empirical equations for fast approximate calculation of the dissociation degrees and pH values are also suggested. Keywords: Tartaric acid, malic acid, citric acid, succinic acid, degree of dissociation, hydrogen ions concentration, dissociation step, dissociation constants, monoanion, dianion.Download Full Article |
Abstract : Optimising the Design of Fe0-Based Filtration Systems for Water Treatment: The Suitability of Porous Iron Composites
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Abstract: This study assessed the functionality of metallic iron (Fe0) filtration systems using porous iron composite (PIC) as an alternative to granular Fe0/aggregate mixtures. The usage of PIC for water treatment has many challenges which are related to the well-drained nature of highly porous filters and the corresponding increase in hydraulic conductivity (shorter contact time). In this article, the extent of (i) iron exhaustion and (ii) porosity loss in four filtration systems are critically discussed. The considered filtration systems are: (i) Fe0 alone, (ii) PIC alone, (iii) Fe0/sand and (iv) Fe0/pumice. In all four systems, mono-sized granular spherical particles are assumed. Sand and Fe0 are compact (f = 0 %) whereas PIC and pumice are porous (e.g. f = 40 %). Results demonstrated that under anoxic conditions (Fe3O4 as major corrosion products) Fe0 depletion is possible in all systems except Fe0 alone. Under oxic conditions (e.g. formation of Fe(OH)3), the PIC system exhibited the highest level of Fe0 depletion (58 %). The increasing order of sustainability was: Fe0 < Fe0/sand < Fe0/PM < PIC. These results suggested that manufacturing PIC with defined porosity and intrinsic reactivity is the key for more efficient usage of Fe0 for environmental remediation and water treatment. Keywords: Porous media, Permeability loss, Reactive filtration, Water treatment, Zero-valent iron.Download Full Article |
