Spectrophotometric determination of selenium(IV) with 4-methyl-<Emphasis Type="Italic">o</Emphasis>-phenylenediamine based on piazselenol formation

A method has been developed for the spectrophotometric determination of selenium(IV) using 4-methyl-o-phenylenediamine (MOPDA) as a chromogenic reagent. In hydrochloric acid media at about pH 2, MOPDA forms a piazselenol complex with selenium(IV), which gives an absorption maximum at 332 nm. After transfer of the formed piazselenol complex into organic phase with n-hexane, the absorbance of the piazselenol complex was measured by a UV-Vis spectrophotometer. The effective parameters of the experimental conditions such as pH, formation time of the complex, amount of MOPDA, ionic strength, volume of sample and effects of diverse ions, were investigated. The detection limit of the proposed method was found to be 0.95 μg/L Se(IV) (n = 14, 3σ). The method was successfully applied to tap water, sea water and wastewater samples from washings of flue gases with satisfactory results.     

Cold valleys of superheavy elements with deformed targets and projectiles

The dependence of the cold driving potential on the deformation of the incoming target and projectile is investigated in the case of the synthesis of the superheavy nuclei ²⁵⁶No, ²⁸⁶112, ²⁹²114, ²⁹⁶116, and ³⁰⁶122. The occurrence of valleys in the driving potential as a function on the interfragment distance and the mass asymmetry is studied for different fixed orientations of the colliding nuclei such as the pole-pole, pole-equator, equator-equator, and equator-equator-crossed and compared to the case when the nuclei are assumed to be spherical or when the potential is averaged over the orientation.     

Synthesis and characterization of some <Emphasis Type="Italic">vic</Emphasis>-dioxime and its mononuclear complexes

In this study, acetophenone is used as a basis substance. ω-Isonitrosoacetophenone has been synthesized from nitrosyl with amyl nitrite of acetophenone in the presence of sodium ethoxide. Subsequently, anti-phenylglyoxime has been prepared by reacting ω-isonitrosoacetophenone with hydroxylamine and sodium acetate in a ethanolic media. Chlorophenylglyoxime has been obtained from reaction with chlorine gases. Then, three aminophenylglyoxime (ligands) have been prepared by the reaction of chlorophenylglyoxime and the corresponding amines. The Ni(II), Co(II), and Cu(II) complexes with BF²⁺-bridge of anilinophenylglyoxime and 2,4-dimethylanilinophenylglyoxime were prepared. Then polymeric metal complexes with BF²⁺-bridge of dopamiophenylglyoxime were prepared. Their structures were identified by FT-IR, ¹H NMR, and ICP-AES spectral data, elemental analysis and magnetic measurements. The article was submitted by the authors in English. An erratum to this article is available at .     

Collective excitations of the element <Emphasis Type="Italic">Z</Emphasis> = 120

The low-lying vibrational excitations of superheavy even-even nuclei around Z=120 and N=172, predicted to be spherical by the relativistic mean-field (RMF) model, are studied within a phenomenological collective approach. In the framework of the macroscopic model for giant resonances, we compute the transition densities of the isoscalar monopole, quadrupole, and octupole and isovector dipole modes for the superheavy nucleus ²⁹²120, whose ground-state density is determined from the RMF model. The results are also compared to those for²⁰⁸Pb.     

Calculated hyperfine coupling constants for 5,5-dimethyl-1-pyrroline N-oxide radical products in water and benzene

The optimized structures of some radical adducts of 5,5-dimethyl-1-pyrroline N-oxide were computed by different methods on ESR spectra. As trapped radicals, H, N₃, NH₂, CH₃, CCl₃, OOH in water and F, OH, CF₃, CH₂OH, OC₂H₅ in benzene solutions were used. The calculated isotropic hyperfine coupling constants of all the trapped radicals were compared with the corresponding experimental data. The hyperfine coupling constant due to the β proton of the nitroxide radical was seen to be consist with the McConnel’s relation α_β = B ₀ + B ₁cos²θ and, to be effected with the opposite spin density of oxygen nucleus bonded to the nitrogen. It was concluded that in hyperfine calculations the DFT(B3PW91)/LanL2DZ level is superior computational quantum model relative to the used other level. Also, the study has been enriched by the computational of the optimized geometrical parameters, the hyper conjugative interaction energies, the atomic charges and spin densities for all the radical adducts.     

Removal of Cu(II), Zn(II) and Co(II) ions from aqueous solutions by adsorption onto natural bentonite

In this study, the removal of Cu(II), Zn(II) and Co(II) ions from aqueous solutions using the adsorption process onto natural bentonite has been investigated as a function of initial metal concentration, pH and temperature. In order to find out the effect of temperature on adsorption, the experiments were conducted at 20, 50, 75 and 90 °C. For all the metal cations studied, the maximum adsorption was observed at 20 °C. The batch method has been employed using initial metal concentrations in solution ranging from 15 to 70 mg L⁻¹ at pH 3.0, 5.0, 7.0 and 9.0. A flame atomic absorption spectrometer was used for measuring the heavy metal concentrations before and after adsorption. The percentage adsorption and distribution coefficients (K _d) were determined for the adsorption system as a function of adsorbate concentration. In the ion exchange evaluation part of the study, it is determined that in every concentration range, adsorption ratios of bentonitic clay-heavy metal cations match to Langmuir, Freundlich and Dubinin-Kaganer-Radushkevich (DKR) adsorption isotherm data, adding to that every cation exchange capacity of metals has been calculated. It is shown that the bentonite is sensitive to pH changes, so that the amounts of heavy metal cations adsorbed increase as pH increase in adsorbent-adsorbate system. It is evident that the adsorption phenomena depend on the surface charge density of adsorbent and hydrated ion diameter depending upon the solution pH. According to the adsorption equilibrium studies, the selectivity order can be given as Zn²⁺>Cu²⁺>Co²⁺. These results show that bentonitic clay hold great potential to remove the relevant heavy metal cations from industrial wastewater. Also, from the results of the thermodynamic analysis, standard free energy ΔG ⁰, standard enthalpy ΔH ⁰ and standard entropy ΔS ⁰ of the adsorption process were calculated.     

Reversible film formation from nano-sized PNIPAM particles below glass transition

Reversible film formation process from nano-sized Poly(N-isopropylacrylamide) (PNIPAM) microgel particles were studied during heating-cooling cycles at various rates. Photon transmission technique was used and transmitted photon intensity I _tr was monitored during heating–cooling cycles. The increase and decrease in I _tr during heating and cooling was explained with the void closure and void reconstruction processes, and the corresponding activation energies were measured. It was observed that PNIPAM microgels required less energy during reconstruction of voids than their closure.