Removal of Brilliant Green from wastewater using conventional and ultrasonically prepared poly(acrylic acid) hydrogel loaded with kaolin clay: A comparative study

The present work deals with the removal of Brilliant Green dye from wastewater using a poly(acrylic acid) hydrogel composite (PAA-K hydrogel) prepared by incorporation of kaoline clay. The composite has been synthesized using ultrasound assisted polymerization process as well as the conventional process, with an objective of showing the better effectiveness of ultrasound assisted synthesis. It has been observed that the hydrogel prepared by ultrasound assisted polymerization process showed better results. The optimum conditions for the removal of dye are pH of 7, temperature of 35 °C, initial dye concentration of 30 mg/L and hydrogel loading of 1 g. The extent of removal of dye increased with an increase in the contact time and initial dye concentration. A pseudo-second-order kinetic model has been developed to explain the adsorption kinetics of dye on the PAA-K hydrogel. Thermodynamic and kinetic parameters indicate that the adsorption process is spontaneous in nature and the PAA-K hydrogel prepared by ultrasound process is a promising adsorbent compared to conventional process. The obtained adsorption data has also been fitted into commonly used adsorption isotherms and it has been found that Freundlich as well as Langmuir adsorption isotherm models fits well to the experimental results.     

Electroosmosis modulated peristaltic biorheological flow through an asymmetric microchannel: mathematical model

A theoretical study is presented of peristaltic hydrodynamics of an aqueous electrolytic non-Newtonian Jeffrey bio-rheological fluid through an asymmetric microchannel under an applied axial electric field. An analytical approach is adopted to obtain the closed form solution for velocity, volumetric flow, pressure difference and stream function. The analysis is also restricted under the low Reynolds number assumption (Stokes flow) and lubrication theory approximations (large wavelength). Small ionic Peclét number and Debye–Hückel linearization (i.e. wall zeta potential ≤ 25 mV) are also considered to simplify the Nernst–Planck and Poisson–Boltzmann equations. Streamline plots are also presented for the different electro-osmotic parameter, varying magnitudes of the electric field (both aiding and opposing cases) and for different values of the ratio of relaxation to retardation time parameter. Comparisons are also included between the Newtonian and general non-Newtonian Jeffrey fluid cases. The results presented here may be of fundamental interest towards designing lab-on-a-chip devices for flow mixing, cell manipulation, micro-scale pumps etc. Trapping is shown to be more sensitive to an electric field (aiding, opposing and neutral) rather than the electro-osmotic parameter and viscoelastic relaxation to retardation ratio parameter. The results may also help towards the design of organ-on-a-chip like devices for better drug design.     

Fly ash supported NiO as an efficient catalyst for the synthesis of xanthene and its molecular docking study against plasmodium glutathione reductase

A novel fly ash supported NiO (FA–NiO) nanocomposite solid heterogeneous catalyst has been prepared by impregnation of Ni(NO₃)₂ · 6H₂O on thermally activated fly ash (FA) support. FT-IR spectroscopy, X-ray diffraction analysis, scanning electron microscopy, TEM and BET techniques were employed to characterize the catalyst. The catalytic adeptness of FA–NiO was tested and optimized in xanthene formation. Catalyst gave very high yield and good purity. Stability of the catalyst could be promising as it easily recovered and reused giving a similar yield up to four cycles. FA–NiO is an efficient catalyst providing an environmentally clean process for xanthene formation and for developing a revolutionary way to use the majority of waste fly ash. Further, we have also performed docking simulation between 1ONF and a xanthene molecule to evaluate binding orientation and affinity of the ligand.     

Pyrolysis-controlled synthesis and magnetic properties of sol–gel electrospun nickel cobaltite nanostructures

Poly(chloropropyl-methyl)silsesquioxanes (PCMSQ) were prepared using the base catalyzed sol–gel processing on methyltrimethoxysilane (MTMS) and 3-chloropropyltriethoxysilane (CPTES) with 5:5, 6:4, and 7:3 molar ratios in methanol and water. The PCMSQ with 6:4 molar ratio of MTMS:CPTES, which has the maximum yield, according to the elemental analysis, was chosen and some chlorine atoms of the chloropropyl groups were changed to different amines by refluxing it with ethylenediamine (en), diethylenetriamine (dien), ortho-phenylenediamine (opda), and 2-imidazolidinethion (imt). The amine grafted PCMSQ were then used to support MoO₂(acac)₂ complex and dien grafted PCMSQ with higher metal content was applied to the epoxidation of cis-cyclooctene with TBHP. The product yields were studied by gas liquid chromatography and the catalytic procedure was optimized for the parameters involved such as the solvent and oxidant. The catalytic activity of this catalyst also was investigated toward epoxidation of some other alkenes. It was also applied to check its reuse ability.

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In this research, micro-spherical poly-organo-silsesquioxane was prepared using the base catalyzed sol–gel processing of methyltrimethoxysilane and 3-chloropropyltriethoxysilane with different molar ratios. The sample which has the maximum yield, was used to graft MoO₂(acac)₂ and for the successful anchoring, some chlorine atoms of the chloropropyl side groups were changed to amines. Then the prepared catalyst with higher molybdenum content was used for the epoxidation of cis-cyclooctene and some other alkenes with TBHP.

     

Compact Rack Shaped MIMO Dielectric Resonator Antenna with Improved Axial Ratio for UWB Applications

Wireless Personal Communications - In this paper, a rack shaped two radiator element multiple input multiple output (MIMO) dielectric resonator antenna (DRA) is reported with improved axial ratio...     

Bandwidth packing problem with queueing delays: modelling and exact solution approach

In this paper we develop a general but smooth global optimization strategy for nonlinear multilevel programming problems with polyhedral constraints. At each decision level successive convex relaxations are applied over the non-convex terms in combination with a multi-parametric programming approach. The proposed algorithm reaches the approximate global optimum in a finite number of steps through the successive subdivision of the optimization variables that contribute to the non-convexity of the problem and partitioning of the parameter space. The method is implemented and tested for a variety of bilevel, trilevel and fifth level problems which have non-convexity formulation at their inner levels.     

Palladium complexes of amido-functionalized N-heterocyclic carbenes as effective precatalysts for the Suzuki-Miyaura C-C cross-coupling reactions of aryl bromides and iodides

A series of air-stable, robust and highly active palladium based precatalysts of amido-functionalized N-heterocyclic carbenes for the Suzuki-Miyaura C-C cross-coupling reaction has been designed. In particular, the [1-R-3-{N-(benzylacetamido)imidazol-2-ylidene]₂PdCl₂ [R = i-Pr (1c) and CH₂Ph (2c)] complexes efficiently carried out the Suzuki-Miyaura coupling of the aryl bromide and iodide substrates with phenyl boronic acid in good to excellent yields in air at 90 °C in 12 h. Quite interestingly, of these palladium precatalysts, the i-propyl derivative (1c) exhibited superior activity as compared to the benzyl derivative (2c). The density functional theory (DFT) studies carried out on the 1c and 2c complexes revealed the strong σ-donating nature of the NHC ligand as reflected in their high d/b ratio [i.e. forward σ-donation (d) to backward π-donation (b)] of these complexes and, thus, point towards greater stability of the Pd-NHC interaction in these complexes.     

Spontaneous CdTe --> alloy --> CdS transition of stabilizer-depleted CdTe nanoparticles induced by EDTA

CdTe nanoparticles stabilized by l-cysteine are chemically transformed into CdS nanoparticles of the same diameter via an intermediate CdTeS alloy without any auxiliary source of sulfur. The reaction is induced by ethylenediaminetetraacetic acid dipotassium salt dehydrate (EDTA), which was demonstrated experimentally to act as a catalyst by partially removing thiol stabilizers from the nanoparticle surface. It is hypothesized that addition of EDTA facilitates Te(2-) release, and oxidation of Te(2-) drives the nanoparticle transition process. Unlike many reports on reactions catalyzed by nanocolloids, this is likely to be the first observation of a catalytic reaction in which nanoparticles function as a substrate rather than a catalyst. It opens new pathways for the synthesis of novel nanoscale II-VI and other semiconductors and represents an interesting case of chemical processes in nanocolloids with reactivity increased by depletion of the surface layer of thiol stabilizers. This includes but is not limited to accurate control over the particle composition and crystallization rate. The slow rate of the CdTe --> alloy --> CdS transition is important for minimizing defects in the crystal lattice and results in a substantial increase of the quantum yield of photoluminescence over the course of the transition.