Facile synthesis,characterization and application of magnetic Fe3O4-coir pith composites for the removal of methyl violet from aqueous solution: Kinetics,isotherm, thermodynamics and parametric optimization

Dyes are commonly used in coloring clothes; in fertilizers, as anti-freezers, as detergents and so on. The use of such dyes has carcinogenic and genotoxic effects. These dyes require proper removal from the environment. Subsequently, a green and low-cost approach promises to adhere to sustainability of the environment while maximum removal of these toxic dyes. The present study describes removal of methyl violet (MV) dye by adsorption process magnetically separable Fe₃O₄-coir pith composites. The study was evaluated in batch system taking the optimum conditions as: pH: 7, contact time: 12 h, stirring speed: 200 rpm, concentration of dye: 100 mg/L, adsorbent weight: 3 g/L, temp.: 308 K. The central composite design approach of response surface methodology in design-expert software showed maximum removal efficiency (>98%) for optimal parameters. The experimental equilibrium data fitted reasonably well to Langmuir isotherm model. ANOVA analysis along with Fisher's statistical test was also performed to validate the model. The predicted model was at par with the experimental values with adjusted R² of 0.9914. A thorough investigation of kinetic ($R_{\text{Pseudo second order}}^2$ = 0.99; $R_{\text{Pseudo second order}}^2=0.97;R_{\text{intra}?\text{particle diffusion}}^2=0.98)$, thermodynamic, adsorption isotherm $(R_{\text{Langmuir isotherm}}^2=0.997$ $R_{\text{Freundlich isotherm}}^2=0.99$ and eco-toxicological characteristics were performed for proper evaluations of the properties as well as sustainability of the adsorbent material. The whole research indicated encouraging potential of the developed material for adsorption, reusability and sustainability in applications for industrial scale wastewater treatment.     

Rheological behavior of viscoelastic wormlike micelles in mixed sodium dodecyl trioxyethylene sulfate–monolaurin aqueous system

Rheological behavior of viscoelastic wormlike micelles in an aqueous system of mixed sodium dodecyl trioxyethylene sulfate (SDES)–monolaurin (ML) is presented. Dilute aqueous solution of SDES has a high fluidity and follows Newtonian liquid-like behavior due to formation of small globular type of micellar structure. Addition of lipophilic nonionic cosurfactant ML to dilute or semidilute solution of SDES decreases the interfacial curvature of the aggregates favoring one dimensional micellar growth, and hence, viscosity increases. After a certain concentration of ML, the elongated micelles get entangled with each other leading to the formation of viscoelastic wormlike micelles. The viscoelastic solution follows Maxwell model of a single stress relaxation mode at low-frequency region. Further addition of ML decreases the viscosity of the solution due to formation of micellar joints in the network structure. The viscosity of the viscoelastic wormlike micelles decreases upon heating, and the system with poor viscoelastic character is observed at higher temperatures.     

Molecular structure and spectra of bis (1,4-dimethylpyridinium)-tetrachlorocuprate(II)

Reaction of 1,4-dimethylpyridinium chlorosulphite with anhydrous copper(II) chloride in an atmosphere of dry nitrogen yields an ionic complex containing discrete [CuCl₄]^2– anions and 1,4-dimethylpyridinium cations. Electronic (solid and in solution), far infrared and¹H NMR spectral data predict a distortedT _d structure which has been confirmed by X-ray crystallography. The crystal structure was solved by the heavy-atom method and refined by full-matrix least squares toR=0.059 for 1685 observed reflections. The [CuCl₄]^2– anions exhibit twofold symmetry and there are no unusual interactions with the cations. Bond lengths and angles place it in the select class of complexes with the least flattenedT _d structure.     

Polyoxyethylene cholesteryl ether-based aqueous wormlike micelles

Formation of wormlike micelles (WLMs) in an aqueous mixture of polyoxyethylene cholesteryl ether (ChEO_n; where n = 20 and 30) and polyoxyethylene dodecyl ether (C₁₂EO_m; where m = 3 and 4) has been reported; rheological and small angle X-ray scattering (SAXS) measurements have been performed in the micellar solutions of ChEO_n as a function of C₁₂EO_m for the structural elucidation. When lipophilic cosurfactant, C₁₂EO_m is added to the micellar solutions of ChEO_n, it favors the sphere-to-cylinder transition due to the penetration of C₁₂EO_m in the palisade layer of ChEO_n micelle accompanying an increase in viscosity. When the concentration of C₁₂EO_m is increased, entangled network of WLMs is formed. A strong shear thinning has been observed in highly viscous samples indicating the presence of transient networks. Such samples exhibited viscoelastic behavior and could be described by the Maxwell model with a single stress relaxation mode. A maximum is observed in zero-shear viscosity-C₁₂EO_m plot. With further addition of C₁₂EO_m, viscosity declines and ultimately a phase separation occurs with the formation of turbid solution of vesicular dispersion. This decline has been interpreted in terms of micellar branching induced by an increase in endcap energy, E _c (which is compensated by the formation of branch points, having a mean curvature opposite to that of endcaps). The C₁₂EO_m induced one-dimensional micellar growth has been confirmed by SAXS.     

Polyfluorophenylamino Germanes and Their Titanium (IV) Chloride Adducts

Disproportionation reactions between (CF ₃ CH ₂ O) ₃ GeNHC ₆ H _{5 ? n} F _n and TiCl ₄ in petroleum ether (40?60°C) at 0° to ?10°C give (CF ₃ CH ₂ O) ₂ Ge(NHC ₆ H _{5 ? n} F _n ) ₂ ^.2TiCl ₄ and (CF ₃ CH ₂ O)Ge(NHC ₆ H _{5 ? n} F _n ) ₃ ^. 2TiCl ₄ adducts. However, complete disproportionation of (CF ₃ CH ₂ O) ₃ Ge(NHC ₆ H _{5 ? n} F _n ) (n = 1,2) occurs at ?55 to ?60°C to give Ge(NHC ₆ H _{5 ? n} F _n ) ₄ ^.3TiCl ₄ . These complexes give double adducts on reactions with CH ₃ NO ₂ and CH ₃ CN. All the products are characterized by elemental analyses and IR, ¹ H, and ¹⁹ F NMR spectroscopy. A comparative disproportionation of the germanamines and analogous silanamines is discussed.     

Interfacial Properties of Aqueous Nonionic Fluorocarbon Surfactant Solutions

The equilibrium, dynamic surface tensions, and surface dilatational elasticity of aqueous solutions of nonionic fluorocarbon surfactant are reported. The critical micellar concentration, CMC (0.023 mM) and equilibrium surface tension (24.6 m N . m^?1) at CMC were measured by Wilhelmy plate method for aqueous solution of C₈F₁₇SO₂N(C₃H₇)(C₂H₄O)_nH (n=20), abbreviated as EF122A. The surface tension decay is slower for C₈F₁₇SO₂N(C₃H₇)(C₂H₄O)_nH (n=10) system, abbreviated as EF122B compared to the EF122A system over short time region, which indicates the slow transport of the surfactant molecules to the surface. The relaxation time for surface tension decay is estimated by fitting a series of exponentials to the dynamic surface tension data and it decreases with temperature for EF122A. Slow exchange of monomers between bulk and interface is reflected in the high elasticity value of the air‐liquid interface for EF122B compared with EF122A within measured frequency window (0.125–1.25 Hz).     

Nonlinear Dynamic Bending Analysis of Plates Using a Higher-Order Shear Deformation Theory

The transient dynamic elastoplastic bending analysis of plates is investigated. Higher-order shear deformation theory is employed for the purpose, so as to have more realistic transverse shear representation. The formulation requires C⁰ continuity for nodal variables. Isoparametric parabolic finite element discretization is adopted. The yield criteria incorporated are von Mises and Tresca along with associated flow rules. The isotropic hardening is also included. Equations of motion are satisfied at discrete time intervals using direct integration method and central difference scheme. A special mass lumping scheme is adopted. As critical time step is very important in explicit integration scheme, precaution has been taken so as to have the time step smaller than the critical one. Numerical examples are solved and compared with solutions from literature. The formulation is shown to be superior in comparison to previous formulations, being more generic in all respects.     

The effect of peripheral bipyridine ligands on the photocatalytic hydrogen production activity of Ru/Pd catalysts

A pyrazine bridged ruthenium/palladium bimetallic photocatalyst with peripheral 4,4'-dicarboxyethyl-2,2'-bipyridine ligands, EtOOC-RuPd, is reported, together with its 2,2'-bipyridine analogue. Upon irradiation with visible light, EtOOC-RuPd catalyses the production of hydrogen gas whereas the complex RuPd does not.     

Fabrication and optical study of Ag@SnO<Subscript>2</Subscript> core-shell structure nanoparticle thin films

Ag@SnO₂ core-shell nanoparticles dispersed in poly-(vinyl) alcohol films were fabricated on glass substrate by employing a dip-coating technique. Synthesis of Ag@SnO₂ nanoparticles with core-shell morphology is carried out by a soft-chemical technique in aqueous phase at 60°C. Formation of core-shell structure is monitored by the red-shift of the surface plasmon band of Ag nanoparticles (from 390 to 410 nm) in the UV-visible spectrum. These nanoparticles are deposited on the glass substrate. The structure and morphology of these films were investigated by X-ray diffraction technique and field-emission transmission electron microscopy, respectively. Optical properties of these pseudo-solids were studied by UV-visible spectroscopy. Surface plasmon spectrum of the core-shell nanoparticles film remained unaltered with increase in the number of layers. However, silver nanoparticles films have shown peak broadening and development of additional peaks with increase in the number of layers. Our investigations showed that the surface plasmon band of the silver nanoparticles could be preserved by controlled deposition of the tin dioxide shell.