Comparison of polymeric and ceramic membranes performance in the process of micellar enhanced ultrafiltration of cadmium(II) ions from aqueous solutions

A comparison of polymeric and ceramic membranes in the ultrafiltration process was studied and presented. This study was conducted on the separation of cadmium(II) ions, with particular reference to parameters such as hydrodynamic permeability coefficient, membrane fouling, amount of surfactant in the permeate, efficiency, and effectiveness of the process. The effect of ionic (SDS) and non-ionic (Rofam 10) surfactants or their mixture was investigated. The hydrodynamic permeability coefficient of the ceramic membrane was found to be much lower in comparison to those of the polymeric ones (1.69 × 10^?7 m³ h^?1 m^?2 Pa^?1, 5.66 × 10^?7 m³ h^?1 m^?2 Pa^?1, and 9.26 × 10^?7 m³ h^?1 m^?2 Pa^?1 for ceramic, CA, and PVDF, respectively). However, filtration of the surfactants solutions did not cause permanent blocking of pores and the surface of the ceramic membrane in contrast to the polymeric ones. No significant differences in surfactants permeation through the membranes tested were observed. Concentration of the surfactant in the permeate was lower than 1 CMC for the Rofam 10 solution and exceeded the CMC by about 40 % for the SDS solution. Better separation properties of polymer membranes for the separation of cadmium(II) ions from micellar systems were identified.     

Reactivity of 2-formylphenylboronic acid toward secondary aromatic amines in amination-reduction reactions

The synthesis of 2-(arylaminomethyl)phenylboronic acid via an amination-reduction reaction has been investigated within a model system comprising 2-formylphenylboronic acid and N-ethylaniline. Adoption of the appropriate reaction conditions influences the reactivity of 2-formylphenylboronic acid, enabling efficient synthesis of so-far unobtainable 2-(arylaminomethyl)phenylboronic compounds. The first crystal structure of the aromatic amine derivative has been determined and described.     

On Trivial Extensions of 2-Fundamental Algebras #

There are considered trivial extensions of minimal 2-fundamental algebras. It is shown that if the Auslander–Reiten quiver Γ _A of a minimal 2-fundamental algebra A contains a starting component or an ending component which is not generalized standard, then the Auslander–Reiten quiver Γ _T(A) of the trivial extension T(A) of A contains also a component that is not a generalized standard.     

Raman study of KMnF3 perovskite crystals doped by Na+

A study of the influence of cationic Na⁺ substitution in the archetype KMnF₃ perovskite crystal was performed using the Raman method. The Raman spectra of mixed K_1-xNa_xMnF₃ crystals with x = 0.029, 0.048 and 0.065 were recorded versus temperature and fully interpreted in terms of a “one mode” behaviour. In addition to the soft mode not completely vanishing close to Tc, attention was especially paid to evidence of static and dynamical disorder. From this point of view the behaviour of the hard Raman modes versus temperature has been studied together with two unexpected Raman bands in the cubic phase. The interpretation has been made within the more general framework of structural disorder existing in such perovskites with anisotropic interactions.     

Diamond Composites with TiC,SiC and Ti 3 SiC 2 Bonding Phase

The problems connected with producing diamond composites with 30 wt.% of bonding phase in form of: SiC, TiC, and Ti 3 SiC 2 are presented in the paper. Increasing the fraction of the bonding phase within the composite generally helps to reduce internal stresses. Composites were sintered at pressure 8.0 - 0.2 GPa and temperature of 2070 - 50 K using the Bridgman type high pressure apparatus. Interactions in the diamond-SiC, the diamond-TiC, and the diamond-Ti 3 SiC 2 systems were studied by means of transmission electron microscope (TEM) and X-ray diffraction. Density was measured pycnometrically. The wear resistance studies of these composites were carried out using pin - on disc type laboratory equipment. Hardness was measured with Vickers apparatus. Results of measurements of physical and mechanical properties are reported.     

Zinc-mediated allylation of aldoxime esters

A facile zinc-mediated Barbier-type allylation of aromatic aldoxime esters, producing the corresponding protected homoallylic hydroxylamines, which are readily converted into homoallylic hydroxamic acids, is described.     

Radioactivity of honey from northern Poland

This work shows significant variations in the values of ²¹⁰Po in different analyzed Polish voivodeships. Statistical analysis of ²¹⁰Po activity concentrations in honey samples showed significant differences between place of honey collecting, kind of honey and morphological structure of plants from which bees collected nectar.

     

Direct Comparison of the Reactivity of Model Complexes for Compounds 0, I,and II in Oxygenation,Hydrogen‐Abstraction,and Hydride‐Transfer Processes

The iron(III) meso‐tetramesitylporphyrin complex is a good biomimetic to study the catalytic reactions of cytochrome P450. All of the three most discussed reactive intermediates concerning P450 catalysis (namely, Cpd 0, Cpd I, and Cpd II) can be selectively produced, identified, and stabilized for many minutes in solution at low temperature by choosing appropriate reaction conditions. In this way, their reactivity against various substrates was determined by utilizing low‐temperature rapid‐scan UV/Vis spectroscopy. Since all reactive intermediates are derived from a single model complex, the results of these kinetic measurements provide for the first time a full comparability of the determined rate constants for the three intermediates. The rate constants reveal a significant dependence of the reactivity on the type of reaction (e.g., oxygenation, hydrogen abstraction, or hydride transfer), which closely correlates with the chemical nature of Cpds 0, I, and II. The detailed knowledge of the reactivity of these intermediates provides a valuable tool to evaluate their particular role in biological systems.     

The self‐disproportionation of enantiomers (SDE): The effect of scaling down,potential problems versus prospective applications,possible new occurrences,and unrealized opportunities?

This commentary discusses an important, though not widely appreciated, chiral phenomenon of molecular chirality that effectively always occurs whenever nonracemic samples are subjected to practically any physicochemical process (e.g., force field, recrystallization, sublimation, even distillation, etc.) under totally achiral conditions external to the sample itself. The phenomenon is termed as the self‐disproportionation of enantiomers (SDE) and though ubiquitous, its presence may not always be readily apparent, or workers may be otherwise oblivious to its effects. In the particular case of chromatography, when the SDE is apparent, the enantiomeric excess (ee) of the chiral compound is observed to vary across an eluted peak, with anterior eluted portions either enantioenriched or enantiodepleted relative to the ee of the starting material, and conversely for the posterior eluted portions. Herein, we highlight various aspects of the SDE phenomenon as it pertains to chromatography and, in particular, the effect of scaling down chromatographic systems, the potential risk of problems that the SDE can cause, as well as opportunities for practical applications of the phenomenon, possible new occurrences of the SDE phenomenon to be searched for, and unrealized opportunities.     

Advantages of Amperometric Readout Mode of Ion‐selective Electrodes under Potentiostatic Conditions

Amperometric responses of all‐solid‐state ion‐selective electrodes, recorded under potentiostatic conditions, were studied on example of potassium‐selective sensors with polypyrrole solid contact, at potential corresponding to reduction of the solid contact material and accompanying transfer of potassium ions across the membrane. Selective and stable in time linear dependences of current vs. logarithm of analyte concentration were recorded, resulting from high membrane resistance and changing membrane potential. The influence of experimental parameters as applied potential or thickness of the membrane was discussed. Advantages of the amperometric mode compared to potentiometric one relate to possibility of tailoring analytical parameters (sensitivity, magnitude of the signal) as well as over one order of magnitude decrease of the detection limit. The latter effect is achieved due to externally forced incorporation of potassium ions from the solution to the membrane, compensating their spontaneous release to the sample solution. A method of experimental setup simplification was proposed, with application of two‐electrode system, which can be used in the absence of external polarization source. The required driving force for the current flow was assured by spontaneous oxidation process occurring at the second electrode, coupled with reduction of the solid contact material of the ion‐selective electrode. In this case also stable in time calibration plots can be recorded.