A biopolymer-based composite hydrogel for rhodamine 6G dye removal: its synthesis,adsorption isotherms and kinetics

The present study reports the preparation and application of a novel biopolymer-based composite hydrogel (BCH) for removal of synthetic dye rhodamine 6G (Rh6G). BCH was prepared from biopolymer chitosan and acrylic acid monomer, in the presence of initiator (K₂S₂O₈) and cross-linker thiourea using microwave irradiation. Synthesized chitosan-based composite hydrogel was characterized by using analytical techniques including Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), derivative thermogravimetric analysis (DTA) and differential thermal analysis (DTG). The stability of the adsorbent was demonstrated from its water uptake capacity. The dynamics of water sorption study showed the Fickian behavior. The investigations were continued to assess the adsorption potential of BCH for removal of Rh6G from aqueous solution. The effect of process parameters affecting the adsorption of rhodamine 6G (Rh6G), such as adsorbent dose, initial concentration of pollutant, contact time and pH of the solution was evaluated. Removal efficiency of chitosan-based composite hydrogel (BCH) was found to be 87.31% at pH 7 for BCH dose of 1 g/L after 8 h. The obtained data were fitted to adsorption isotherms and kinetics models. The adsorption equilibrium isotherm and kinetics studies indicated that the pseudo-second-order model and the Freundlich model well described the adsorption equilibrium of Rh6G on BCH.     

Microwave-assisted synthesis and characterization of tin oxide nanoparticles

Tin oxide nanoplatelets (SnO) and nanoparticles (SnO₂) were prepared by microwave assisted technique with an operating frequency of 2.45 GHz. This technique permits to produce gram quantity of homogeneous nanoparticles in just 10 min. The crystalline size was evaluated from XRD and found to range from 26 to 34 nm. SEM and TEM analyses showed that the nanoparticles present a platelet-like shaped particle or, a pseudo spherical morphology, after calcination at moderate temperature during which the phase transformation from SnO to SnO₂ takes place. Additional FT-IR, density and resistivity measurements were also presented.     

Studies on in vitro release of CPM from semi-interpenetrating polymer network (IPN) composed of chitosan and glutamic acid

Interpenetrating polymer network (IPN) beads consisting of chitosan-glutamic acid were prepared for in vitro study of controlled release of chlorpheniramine maleate (CPM). A viscous solution of chitosan-glutamic acid was prepared in 2% acetic acid solution, extruded as droplets through a syringe to alkalimethanol solution and the precipitated beads were crosslinked using glutaraldehyde solution. Swelling and drug release studies were carried out. Transport of release medium through the semi-IPN depended upon its pH and extent of crosslinking. The structural and morphological studies of beads were carried out by using a scanning electron microscope (SEM). The larger surface area of beads as well as their ease of handling makes them ideal agents of controlled release.     

Pumice stone supported titanium dioxide for removal of pathogen in drinking water and recalcitrant in wastewater

Bactericidal and organic degradation effects of TiO₂ on pumice stone are described in this paper. Immobilization of TiO₂ on pumice stone is easy and efficient method to obtain photocatalytic reactions without the problem of filtration. Pumice stone is soft and available as pellets that can be used in pellets fixed (with cement or poly carbonate) on a slanting plank/glass by coating the preformed TiO₂ over the pellets using simple paint brush for applying the photo catalyst. The treatment of inactivation of bacteria especially E. coli existing in real river waters and also different model organic substrate degradations like acid orange-7, resorcinol, 4, 6-dinitro-o-cresol, 4-nitrotoluene-2-sulfonicacid, isoproturan are studied. Furthermore, TiO₂ over pumice stone loaded in a multi tube reactor gave similar results for the disinfection and detoxification studies.     

Unsteady mixed convection flow of a thermomicropolar fluid on a long thin vertical cylinder

The unsteady laminar mixed convection boundary layer flow of a thermomicropolar fluid over a long thin vertical cylinder has been studied when the free stream velocity varies with time. The coupled nonlinear partial differential equations with three independent variables governing the flow have been solved numerically using an implicit finite difference scheme in combination with the quasilinearization technique. The results show that the buoyancy, curvature and suction parameters, in general, enhance the skin friction, heat transfer and gradient of microrotation, but the effect of injection is just opposite. The skin friction and heat transfer for the micropolar fluid are considerably less than those for the Newtonian fluids. The effect of microrotation parameter is appreciable only on the microrotation gradient. The effect of the Prandtl number is appreciable on the skin friction, heat transfer and gradient of microtation.     

Microwave assisted synthesis,spectroscopic, thermal,and antifungal studies of some lanthanide（Ⅲ） complexes with a heterocyclic bishydrazone

A bishydrazone formed by the condensation of isatinmonohydrazone and salicylaldehyde reacted with lanthanide（Ⅲ） chloride to form complexes of the type [Ln（HISA）2Cl3], where, Ln=La（Ⅲ）, Ce（Ⅲ）, Pr（Ⅲ）, Nd（Ⅲ）, Sm（Ⅲ）, Eu（Ⅲ）, or Gd（Ⅲ） and HISA= [（2-hydroxybenzaldehyde）-3-isatin]bishydrazone. Both reactions were carried out under microwave conditions. The ligand and the metal complexes were characterized on the basis of elemental analysis, molar conductance, magnetic susceptibility measurements, UV visible, infrared, far infrared, and proton NMR spectral data. The ligand acted as neutral tridentate, coordinating through the carbonyl oxygen, azomethine nitrogen, and phenolic oxygen without deprotonation. The ligand and lanthanum（Ⅲ） complex were subjected to X-ray diffraction studies. The X-ray diffraction pattern of ligand exhibited its crystalline nature and that of the lanthanum（Ⅲ） complex indicated its amorphous character. The thermal decomposition behaviour of the complex, [La（HISA）2Cl3], was examined in the temperature range of 40-800 ℃ using TG, DTG, and DTA. The ligand and the metal complexes were screened for their antifungal activities.     

Polymer-derived β-SiAlON:Eu2+ phosphors

A series of β-SiAlON:Eu²⁺ phosphors were synthesized from single-source precursors, perhydropolysilazane chemically modified with Al(OCH(CH₃)₂)₃, AlCl₃, and EuCl₂. The single-source precursors were converted to β-SiAlON:Eu²⁺ phosphors by pyrolysis under flowing N₂ or NH₃ at 1000°C, followed by heat treatment at 1800°C under an N₂ gas pressure at 980 kPa. By varying the molar ratio of the chemical modifiers, β-SiAlON:Eu²⁺ with the compositions close to the theoretical ones expressed as Si_6−zAl_zO_z−2yN_8−z+2y:yEu²⁺ were synthesized, where the z values and Eu²⁺ contents were controlled in the ranges of .44–.78 and .35–1.48 mol%, respectively. The polymer-derived β-SiAlON:Eu²⁺ phosphors exhibited green emission under excitation at 460 nm attributed to the 4f⁷–4f⁶(7f³)5d¹ transition of dopant Eu²⁺. High-angle annular dark-field-scanning transmission microscopy analysis confirmed that the doped-Eu²⁺ existed interstitially within the channels along the c axis of host β-SiAlON. Compared with the conventional powder metallurgy route, the polymer-derived ceramic route in this study offers some advantages in the grain growth of host β-SiAlON and photoluminescence properties in terms of green emission intensity under excitation at 460 nm, and the highest intensity was achieved for the polymer-derived β-SiAlON:Eu²⁺ with z = .64 and .37 mol% Eu²⁺.     

Enhanced Photovoltaic Performance of PEDOT:PSS/Si Heterojunction Solar Cell with ZnO BSF Layer: A Simulation Study using SCAPS-1D

Silicon - Here, we report an enhanced photovoltaic (PV) performance including open circuit voltage (Voc), short circuit current (Jsc), fill factor (FF) and power conversion efficiency (PCE) of...