Removal of methyl violet from aqueous solution by perlite

The use of perlite for the removal of methyl violet from aqueous solutions at different concentration, pH, and temperature has been investigated. Adsorption equilibrium is reached within 1 h. The capacity of perlite samples for the adsorption of methyl violet was found to increase with increasing pH and temperature and decrease with expansion and increasing acid-activation. The adsorption isotherms are described by means of the Langmuir and Freundlich isotherms. The adsorption isotherm was measured experimentally at different conditions and the experimental data were correlated reasonably well by the adsorption isotherm of Langmuir. The order of heat of adsorption corresponds to a physical reaction. It is concluded that the methyl violet is physically adsorbed onto the perlite. The removal efficiency (P) and dimensionless separation factor (R) have shown that perlite can be used for removal of methyl violet from aqueous solutions, but unexpanded perlite is more effective.     

Synthesis, characterization, catalytic, electrochemical and thermal properties of tetradentate Schiff base complexes

In this study, the Schiff base ligands H₂L¹–H₂L³ and their Cu^II, Co^II, Ni^II, Fe^III Ru^III and VO^IV complexes have been prepared and characterized by spectroscopic and analytical techniques. All the complexes are mononuclear. Keto-enol tautomeric forms of the ligands have been investigated in polar and apolar solvents. The ligands favor the keto-form in the C₇H₈ and C₆H₁₄. The C–C coupling reaction of the 2,6-di-t-butylphenol has been investigated by the Co^II and Cu^II complexes. Thermal properties of the complexes have been assessed using thermal techniques and similar properties were found. In the Fe^III and Ru^III complexes, firstly, the coordinated water molecule is lost from the complex; in the second step, the chloride ion leaves the molecule in the 300–350 °C temperature range. Finally, the complexes decompose to the appropriate metal oxide at the higher temperature ranges. The electrochemical properties of the complexes have been studied in the two different solvents (DMF and CH₃CN).     

Optimization Strategy for Isocratic Separation of α-Aspartame and Its Breakdown Products by Reversed Phase Liquid Chromatography

α-Aspartame (L-α-aspartyl-L-phenylalanine methyl ester) is increasingly being used in wide variety of commonly consumed food products. This structure contains ester and peptide bonds. The ester linkage may hydrolyze to produce L-α-aspartyl-L-phenylalanine or cyclohydrolyze to produce the corresponding diketopiperazine ring. This ring can open to form L-α-aspartyl-L-phenylalanine and ultimately this compound can hydrolyze to L-phenylalanine and L-aspartic acid. The pH, buffer type, concentration, the presence of water and temperature are other important factors affecting its stability. Because α-aspartame can lose its sweetness under these conditions determination of aspartame and its breakdown products is extremely important for diet foods quality. The optimum mobile phase for the chromatographic separation was found to be acetonitrile-water (20:80, ν/ν) with 5.10^?3 M hexanesulfonic acid and a pH of 2.6.     

Measurement of absolute intensity of 1001 keV gamma-ray of 234mPa

The sorption behavior of ²³⁵U fission fission products ⁹⁹Mo and ¹³²Te was studied through batch and dynamic experiments when they were dissolved in 1 to 7M HNO₃ solutions. It was found that ⁹⁹Mo is always totally adsorbed on hydrated SnO₂, while ¹³²Te is rather weakly adsorbed, therefore they can be separated from each other although ¹³²Te in the solution still remains contaminated with other radionuclides as well as ⁹⁹Mo does in the solid.     

Determination of Na(2)O from sodium aluminate NaAlO(2)

The aim of the work was to find a suitable method and conditions for determining Na(2)O wt.% from NaAlO(2). Problems were encountered while titrating NaAlO(2) with hydrochloric acid. The problematic area was the pH range 4-10 where aluminum precipitates as hydroxides. The different species of the aluminate solution were determined using potentiometric and complexometric titrations. The equivalent point of the potentiometric titration was detected using Gran's plotting method. Precipitation of aluminum hydroxides did not interfere with titrations, because in potentiometric titrations the pH value was over 10 and in complexometric titrations the pH was 4. The results were accurate and determinations were easy to carry out. Sodium was also determined by DCP-AES.     

Hierarchical structure of the energy landscape of proteins revisited by time series analysis. I. Mimicking protein dynamics in different time scales

Time series models, which are constructed from the projections of the molecular-dynamics (MD) runs on principal components (modes), are used to mimic the dynamics of two proteins: tendamistat and immunity protein of colicin E7 (ImmE7). Four independent MD runs of tendamistat and three independent runs of ImmE7 protein in vacuum are used to investigate the energy landscapes of these proteins. It is found that mean-square displacements of residues along the modes in different time scales can be mimicked by time series models, which are utilized in dividing protein dynamics into different regimes with respect to the dominating motion type. The first two regimes constitute the dominance of intraminimum motions during the first 5 ps and the random walk motion in a hierarchically higher-level energy minimum, which comprise the initial time period of the trajectories up to 20-40 ps for tendamistat and 80-120 ps for ImmE7. These are also the time ranges within which the linear nonstationary time series are completely satisfactory in explaining protein dynamics. Encountering energy barriers enclosing higher-level energy minima constrains the random walk motion of the proteins, and pseudorelaxation processes at different levels of minima are detected in tendamistat, depending on the sampling window size. Correlation (relaxation) times of 30-40 ps and 150-200 ps are detected for two energy envelopes of successive levels for tendamistat, which gives an overall idea about the hierarchical structure of the energy landscape. However, it should be stressed that correlation times of the modes are highly variable with respect to conformational subspaces and sampling window sizes, indicating the absence of an actual relaxation. The random-walk step sizes and the time length of the second regime are used to illuminate an important difference between the dynamics of the two proteins, which cannot be clarified by the investigation of relaxation times alone: ImmE7 has lower-energy barriers enclosing the higher-level energy minimum, preventing the protein to relax and letting it move in a random-walk fashion for a longer period of time.     

Quantitative analysis of sea-bed sediments from Eastern Black Sea by EDXRF spectrometry

Sea-bed sediments from Eastern Black Sea have been analyzed for their Fe, Ba and Sr contents using the methods of standard addition and energy dispersive X-ray fluorescence (EDXRF). Samples were prepared from powder sifted by a 200 mesh sieve. An annular 100 mCi²⁴¹Am radioactive source emitting 59.543 keV photons was used for excitation and a Ge(Li) detector, which has a 190 eV FWHM for 5.9 keV photons was used for intensity measurements. 2048 channels of the MCA are employed for 20 or 30 min. Dried and ground sea-bed sediments are found to contain 2.95–7.50% Fe, 0.032–0.268% Ba and about 73–273 ppm Sr. These results agree with those obtained via atomic absorption methods.     

The Adsorption of Polyvinylpyrrolidone on Kaolinite Saturated with Sodium Chloride

The adsorption of two different molecular weights of polyvinylpyrrolidone (PVP) (M(w)=44,000 and M(w)=360,000 g mol(-1)) from water on kaolinite saturated with sodium chloride has been studied. The adsorption of PVP increases slowly as temperature increases. The adsorption of PVP on the kaolinite was studied by considering Fourier transform infrared (FTIR) spectra, X-ray diffraction patterns, and dielectric constants. During the adsorption process, PVP interacts with saturating sodium cations and possibly forces some of them onto the edges of the kaolinite; thus, the dielectric constant of saturated kaolinite is reduced after PVP adsorption. Copyright 2001 Academic Press.     

The inclusion complex of piromidic acid with dimethyl-β-cyclodextrin in aqueous solution and in the solid state

Inclusion complex formation of piromidic acid (PA) with dimethyl--cyclodextrin (DM--CD) in aqueous solution and in the solid state was confirmed by the solubility method, differential scanning calorimetry (DSC) and proton nuclear magnetic resonance (¹H-NMR) spectroscopy. The apparent stability constant,K _c , of the complex was estimated to be 244 M^–1. The stoichiometry of the complex was given as the ratio 1:2 of PA to DM--CD. The dissolution rate of the PA/DM--CD complex was much greater than that of intact PA.Presented at the Fourth International Symposium on Inclusion Phenomena and the Third International Symposium on Cyclodextrins, Lancaster, U.K., 20–25 July 1986.