Influence of operating conditions on the rejection of cobalt and lead ions in aqueous solutions by a nanofiltration polyamide membrane

The potential use of nanofiltration polyamide membrane for removing cobalt and lead ions from wastewater was investigated. Rejection experiments were conducted with Pb(NO₃)₂ and Co(NO₃)₂ in both single-salt solutions and mixtures. Experimental rejection rates were corrected for concentration polarization phenomenon by means of film theory. The structural features of the membrane (pore radius and thickness-to-porosity ratio) were first estimated from the fitting of glucose rejection rates. Its surface charge properties were then investigated in single-salt solutions at pH values between 3 and 7. Rejection of both heavy metal ions was found to be influenced by operating conditions such as permeate flux, solution pH and feed salt concentration. In single-salt solutions, rejection of lead was higher than that of cobalt at pH ≥ 5. This behavior may be explained by (i) higher normalized volume charge density in the Pb(NO₃)₂ than in the Co(NO₃)₂ solution and (ii) lower ionic strength of the Pb(NO₃)₂ solution as compared with the Co(NO₃)₂ solution. At pH < 5, the dielectric exclusion would be more important for Co(NO₃)₂ than for Pb(NO₃). Lead rejection was almost the same in both single-salt solutions and ternary mixtures, whereas cobalt rejection was strongly affected by the presence of lead. Cobalt was found to be rejected much more than lead in mixtures at equal mass concentrations, the difference between rejections of the two cations being greater as pH increased.     

1,3-Thiazoline-2-thione-4,5-dithiolato, an efficient building block towards functionalized dithiadiazafulvalenes

The first synthesis and X-ray structural determination of the bis(tetraethylammonium) Zn dithiolene complex involving N-methyl-1,3-thiazoline-2-thione-4,5-dithiolate, [NEt₄]₂[Zn(Me-thiazdt)₂], are reported. The reactivity of this dithiolene complex as a nucleophilic dithiolate synthon and as a precursor of the air sensitive electron rich olefine, the bis ethylenedithiodithiadiazafulvalene (BEDT-DTDAF), is also described.     

Synthesis of monofunctional curcumin derivatives, clicked curcumin dimer, and a PAMAM dendrimer curcumin conjugate for therapeutic applications

Curcumin, the primary active ingredient in the spice turmeric, was converted to reactive monofunctional derivatives (carboxylic acid/azide/alkyne). The derivatives were employed to produce a 3 + 2 azide-alkyne "clicked" curcumin dimer and a poly(amidoamine) (PAMAM) dendrimer-curcumin conjugate. The monofunctional curcumin derivatives retain biological activity and are efficient for labeling and dissolving amyloid fibrils. The curcumin dimer selectively destroys human neurotumor cells. The synthetic methodology developed affords a general strategy for attaching curcumin to various macromolecular scaffolds.     

An efficient synthesis and reactions of novel indolylpyridazinone derivatives with expected biological activity

Reaction of 4-anthracen-9-yl-4-oxo-but-2-enoic acid (1) with indole gave the corresponding butanoic acid 2. Cyclocondensation of 2 with hydrazine hydrate, phenyl hydrazine, semicarbazide and thiosemicarbazide gave the pyridazinone derivatives 3a-d. Reaction of 3a with POCl(3) for 30 min gave the chloropyridazine derivative 4a, which was used to prepare the corresponding carbohydrate hydrazone derivatives 5a-d. Reaction of chloropyridazine 4a with some aliphatic or aromatic amines and anthranilic acid gave 6a-f and 7, respectively. When the reaction of the pyridazinone derivative 3a with POCl(3) was carried out for 3 hr an unexpected product 4b was obtained. The structure of 4b was confirmed by its reaction with hydrazine hydrate to give hydrazopyridazine derivative 9, which reacted in turn with acetyl acetone to afford 10. Reaction of 4b with methylamine gave 11, which reacted with methyl iodide to give the trimethylammonium iodide derivative 12. The pyridazinone 3a also reacted with benzene- or 4-toluenesulphonyl chloride to give 13a-b and with aliphatic or aromatic aldehydes to give 14a-g. All proposed structures were supported by IR, (1)H-NMR, (13)C-NMR, and MS spectroscopic data. Some of the new products showed antibacterial activity.     

Influence of the aryl substituent identity in 4-arylamino-3-nitrocoumarins on their thermal behavior

Thermal behavior of structurally similar 4-arylamino-3-nitrocoumarin derivatives substituted with different electron-donor and electron-acceptor substituents on the aryl side group was investigated. The thermal stability of these compounds was studied by non-isothermal thermo-gravimetric analysis, differential thermo-gravimetry, differential thermal analysis, and pyrolysis–gas chromatography–mass spectrometry. The thermal degradation of the three synthesized 4-arylamino-3-nitrocoumarins, possessing an iodine atom, a nitro or a methyl group, proceeds in three steps. The thermal stability of the coumarin derivative with the electron-donating methyl substituent is lower than that of the compounds with the electron-accepting nitro group or iodine atom. This least stable compound (4-[(4-methylphenyl)amino]-3-nitro-2H-chromen-2-one) was also characterized with the greatest loss in mass that accompanied the degradation, and all of the three degradation steps of this compound began at the lowest temperature in comparison to the other two.     

Chemical composition,antimicrobial and insecticidal activities of the essential oils of Conyza linifolia and Chenopodium ambrosioides

Two essential oil-containing plants growing wildly in Egypt: Conyza linifolia (Willd.) Täckh. (Asteraceae) and Chenopodium ambrosioides L. (Chenopodiaceae) were subjected to essential oil analysis and biological investigation. The essential oils from both plants were prepared by hydrodistillation, and GC/MS was employed for volatiles profiling. This study is the first to perform GC/MS analysis of C. linifolia essential oil growing in Egypt. C. linifolia essential oil contained mainly sesquiterpenes, while that of C. ambrosioides was rich in monoterpenes. Ascaridole, previously identified as the major component of the latter, was found at much lower levels. In addition, the oils were investigated for their antimicrobial activity against two Gram positive and two Gram negative bacteria, and one fungus. The insecticidal activities of both oils, including mosquitocidal and pesticidal potentials, were also evaluated. The results of biological activities encourage further investigation of the two oils as antimicrobial and insecticidal agents of natural origin.     

Rapid CE‐UV binding tests of environmentally hazardous compounds with polymer‐modified magnetic nanoparticles

Hazardous compounds and bacteria in water have an adverse impact on human health and environmental ecology. Polydopamine (or polypyrrole)‐coated magnetic nanoparticles and polymethacrylic acid‐co‐ethylene glycol dimethacrylate submicron particles were investigated for their fast binding kinetics with bisphenol A, proflavine, naphthalene acetic acid, and Escherichia coli. A new method was developed for the rapid determination of % binding by sequential injection of particles first and compounds (or E. coli) next into a fused‐silica capillary for overlap binding during electrophoretic migration. Only nanolitre volumes of compounds and particles were sufficient to complete a rapid binding test. After heterogeneous binding, separation of the compounds from the particles was afforded by capillary electrophoresis. % binding was influenced by applied voltage but not current flow. In‐capillary coating of particles affected the % binding of compounds.     

Design of fractional-order variants of complex LMS and NLMS algorithms for adaptive channel equalization

Equalization filtering is an effective technique applied to minimize the inter-symbol interference (ISI) in multipath fading channels; the problem gets worse for higher-order constellations which are required for high data rates in today’s communication systems. The least mean square (LMS) filter is a computationally efficient and easily implementable algorithm but suffers from slow convergence; highly complex filters are required to nullify the effects of ISI. In this paper, we develop complex modified fractional-order (FO) nonlinear variants of the LMS and the NLMS algorithms and apply in adaptive channel equalization, in both feed-forward and decision feedback configurations. In addition to the standard first-order derivative, the update in the modified LMS also depends on the FO derivative of the mean square error, the final update is formed using a combination of conventional update term and a nonlinear term obtained through Riemann–Liouville fractional derivative. The step size of the FNLMS scheme in fractional part is not only a function of the input energy but also the FO. The differintegral operator working as differentiator helps improve the convergence rate because the algorithm becomes nonlinear; the fractional algorithms provide more parameters to control the rate of convergence and have simple implementation with almost similar complexity. The performances of the schemes are validated through extensive simulation results for block fading channels (frequency flat and selective) to evaluate the symbol error rate for higher-order quadrature amplitude modulation schemes, mean square error and combined channel and equalizer responses to show the improved inverse modeling of the channel. Simulation experiments confirm the superiority of the proposed algorithm over the traditional counterparts.     

Thermal stability of CR/CSM rubber blends filled with nano- and micro-silica particles

The properties of filled polymers depend on the properties of the matrix and the filler, the concentration of the components and their interactions. In this research we investigated the rheological and mechanical properties and thermal stability of polychloroprene/chlorosulfonated polyethylene (CR/CSM) rubber blends filled with nano- and micro-silica particles. The density of the nano-silica filled CR/CSM rubber blends was lower than that of the micro-silica filled samples but the tensile strength and elongation at break were much higher. The nano-silica filled CR/CSM rubber blend has higher V _r0/V _rf values than micro-silica composites and show better polymer–filler interaction according to Kraus equation. The nano-silica filled CR/CSM rubber blends were transparent at all filler concentration, and have higher glass transition values than micro-silica filled compounds. The higher values of the glass transition temperatures for the nano- than the micro-filled cross-linked systems are indicated by DMA analysis. The nano-filled cross-linked systems have a larger number of SiO–C links than micro-filled cross-linked systems and hence increased stability.     

Microstructure and corrosion properties of diode laser melted friction stir weld of aluminum alloy 2024 T351

Friction stir welding is a promising solid state joining process for high strength aluminum alloys. Though friction stir welding eliminates the problems of fusion welding as it is performed below melting temperature (T_m), it creates severe plastic deformation. Friction stir welds of some aluminum alloys exhibit relatively poor corrosion resistance. This research enhanced the corrosion properties of such welds through diode laser surface melting.A friction stir weld of aluminum alloy 2024 T351 was laser melted using a 1 kW diode laser. The melt-depth and microstructure were investigated using optical and scanning electron microscopy. The melt zone exhibited epitaxially grown columnar grains. At the interface between the melted and the un-melted zone, a thick planar boundary was observed. Energy dispersive spectroscopy analyzed the redistribution of elemental composition. The corrosion properties of the laser melted and native welds were studied in aqueous 0.5 M sodium chloride solution using open circuit potential and cyclic potentiodynamic polarization. The results show noticeable increase in the pit nucleation resistance (390 mV) after the laser surface treatment. The repassivation potential was nobler to the corrosion potential after the laser treatment, which confirmed that the resistance to pit growth was improved.