Surface-modified carbon black for As(V) removal

This paper reports the results of the adsorption performance of As(V) removal by a commercial carbon black and its H2SO4-modified form in a single-ion situation. The influence of different process parameters and the physicochemical principles involved were studied in detail. Acid modification caused morphological changes in the virgin carbon black as evidenced by BET surface area measurements and SEM study. FTIR spectra showed the introduction of sulfonic acid group in the parent carbon due to H2SO4 treatment. TGA analysis revealed higher weight loss characteristics of the modified carbon, demonstrating the creation of functional groups. The point of zero charge (pH pzc) of the modified carbon black is highly acidic (3.5) compared to commercial carbon black (6.4). It directly infers the generation of acidic functional moieties in the carbon black. The adsorption experiments were carried out following batch equilibrium techniques. The kinetics and thermodynamics of adsorption were investigated to unveil the mechanism and nature of the adsorption process, respectively. The kinetic parameters of different models were calculated and discussed. The kinetics of adsorption can be expressed by a pseudo-second-order model and intraparticle diffusion was not the rate-determining step. Dependence of pH on adsorption showed maximum metal uptake in the range of 4-5 and inferred surface complexion as the principal mechanism of adsorption. The equilibrium adsorption data were modeled using Freundlich, Langmuir, and Dubinin-Kaganer-Radushkevich (DKR) isotherm equations and the corresponding isotherm parameters were calculated and discussed in detail.     

Reversal of Regioselectivity in Asymmetric C−H Bond Annulation with Bromoalkynes under Cobalt Catalysis**

Metal-catalyzed asymmetric C−H bond annulation strategy offers a versatile platform, allowing the construction of complex P-chiral molecules through atom- and step-economical fashion. However, regioselective insertion of π-coupling partner between M−C bond with high enantio-induction remain elusive. Using commercially available Co(II) salt and chiral-Salox ligands, we demonstrate an unusual protocol for the regio-reversal, enantioselective C−H bond annulation of phosphinamide with bromoalkyne through desymmetrization. The reaction proceeds through ligand-assisted enantiodetermining cyclocobaltation followed by regioselective insertion of bromoalkyne between Co−C, subsequent reductive elimination, and halogen exchange with carboxylate resulted in P-stereogenic compounds in excellent ee (up to >99 %). The isolation of cobaltacycle involved in the catalytic cycle and the outcome of control experiments provide support for a plausible mechanism.     

Reduced graphene oxide/iron oxide hybrid composite material as an efficient magnetically separable heterogeneous catalyst for transfer hydrogenation of ketones

Reduced graphene oxide was synthesized and functionalized with FeSO₄⋅7H₂O to form a reduced graphene oxide/iron oxide hybrid composite. The hybrid composite was extensively characterized using various techniques. Its application for transfer hydrogenation of various ketones was studied. The investigation showed that it serves as a good catalyst for transfer hydrogenation of aromatic and some aliphatic ketones resulting in excellent isolated yields (97–99%) of products. It is magnetically separable showing good reusability. The products were characterized and compared with authentic ones.     

Grafting a mesomorphic Schiff base onto gold nanoparticle via ester link – photoluminescence,mesomorphism, electrical conductivity and antioxidant activity

Liquid crystal-gold nanoparticle (GNP-LC) composite were accessed via covalent coupling of 4-mercaptophenol capped gold nanoparticles (GNP) and a carboxylic acid functionalised rod shaped mesomorphic Schiff base (LC). The Schiff base ligand and the composite both showed schlieren texture with distinct difference in phase transition temperature. The X-ray diffraction study suggested a smectic C mesophase for the compounds. The LC and GNP-LC, both exhibited room temperature photoluminescence when excited at 264nm.The transmission electron micrography revealed the composite to be nearly monodisphersed having almost spherical shape of ~ 2nm size. The composite material in addition to being mesomorphic exhibited pronounced AC conductivity in the semiconductor domain and antioxidant activity.     

2‐Methyl‐1,3‐disulfoimidazolium polyoxometalate hybrid catalytic systems as equivalent safer alternatives to concentrated sulfuric acid in nitration of aromatic compounds

Ionic liquid‐derived polyoxometalate salts [mdsim]₃[PM₁₂O₄₀] (where M = W and Mo) of two heteropolyacids H₃PW₁₂O₄₀.nH₂O and H₃PMo₁₂O₄₀.nH₂O were synthesized using 2‐methyl‐1,3‐disulfoimidazolium chloride ([mdsim][Cl]) ionic liquid and the corresponding heteropolyacids. Three equivalents of [mdsim][Cl] were treated with the respective Keggin‐structured heteropolyacids (one equivalent) in aqueous medium at room temperature to afford the water‐stable ionic polyoxometalates as acidic solids. They were completely characterized using spectroscopic and other analytical techniques including thermal analysis and Hammett acidity studies. The inherent Brønsted acidic properties of ─SO₃H group of these polyoxometalate salts were studied for the nitration of aromatic compounds with 69% HNO₃ at normal temperature and 80°C without use of any external concentrated sulfuric acid. These strongly acidic polyoxometalates display good recyclability and efficient reusability.     

Nonlinear pulsational eigenmodes of a planar collisional dust molecular cloud with grain-charge fluctuation

We try to present a theoretical evolutionary model leading to the excitations of nonlinear pulsational eigenmodes in a planar (1D) collisional dust molecular cloud (DMC) on the Jeans scale. The basis of the adopted model is the Jeans assumption of self-gravitating homogeneous uniform medium for simplification. It is a self-gravitating multi-fluid consisting of the Boltzmann distributed warm electrons and ions, and the inertial cold dust grains with partial ionization. Dust-charge fluctuations, convections and all the possible collisions are included. The grain-charge behaves as a dynamical variable owing mainly to the attachment of the electrons and ions to the grain-surfaces randomly. The adopted technique is centered around a mathematical model based on new solitary spectral patterns within the hydrodynamic framework. The collective dynamics of the patterns is governed by driven Korteweg-de Vries (d-KdV) and Korteweg-de Vries (KdV) equations obtained by a standard multiscale analysis. Then, simplified analytical and numerical solutions are presented. The grain-charge fluctuation and collision processes play a key role in the DMC stability. The sensitive dependence of the eigenmode amplitudes on diverse relevant plasma parameters is discussed. The significance of the main results in astrophysical, laboratory and space environments are concisely summarized.     

Low-molecular-weight poly-carboxylate as crystal growth modifier in biomineralization

Construction of modified inorganic mineral with controlled mineralization analogues of those produced by nature is now of current interest for understanding the mechanism of thein vivo biomineralization processes, as well as looking for fresh industrial and technological applications. Low-molecular-weight chiral poly-carboxylate ligands derived from naturally occurring L-α-amino acids have been used as model systems to study the effect of molecular properties on crystal growth modification.     

Development of hydrophobic polyurethane film from structurally modified castor oil and its anticorrosive performance

Hydrophobic polyurethane (PU) films are widely used for various commercial and industrial applications due to their excellent water repelling and self-cleaning property. Nevertheless, achieving appreciable hydrophobicity in PU film is quite a challenge. Herein, we report on the development of a novel hydrophobic PU (fluorinated polyurethane [FCO-PU]) film and comprehensively evaluate its anticorrosive property. The FCO-PU was prepared by structural modification of castor oil (CO) through attachment of long fluorocarbon chains as pendant groups onto the backbone of CO. A model PU film (CO-PU) was also prepared from unmodified CO to compare the properties of FCO-PU film. All intermediate compounds, FCO-PU and CO-PU films were characterized by various spectroscopic techniques. Morphological, thermal and mechanical properties of the PU films were analyzed by field emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and dynamic mechanical thermal analysis (DMTA) studies. Successful introduction of long fluorocarbon chains into the FCO-PU film is reflected by its high hydrophobicity with a water contact angle of 119.1°, compared to the model CO-PU film with a water contact angle of 84.4°. Anticorrosive properties of the PU films were evaluated by polarization technique and electrochemical impedance spectroscopy under corrosive environment and the obtained results reveal a significant corrosion resistance (corrosion rate: 6.72 × 10⁻⁶ mm/year) behavior by the FCO-PU film. This work represents an effective strategy for the backbone modification of CO to develop novel functional PU materials.     

Synthesis and Crystal Structure Determination of Dimeric Co(II) and Ni(II) with Pyridine 2,6-Dicarboxylic Acid

Abstract  

Two new dimeric complexes of Ni and Co with pyridine 2,6-dicarboxylic acid were synthesized, the structure of both these complexes were determined by single crystal X-ray crystallography and was characterized spectrally with the help of IR and UV spectrometers and the magnetic moments of both the reported complexes were recorded. Both of these complexes crystallize in the monoclinic space group P 2₁/c1. For the dimeric cobalt complex, formula C₁₄ H₂₁ Co₂ N₂ O₁₅; a = 8.3950(3) ?; α = 90°, b = 27.3702(8) ?; β = 98.211(2)°, c = 9.6235(3) ?; γ = 90° and Z = 3. For the dimeric Nickel complex, formula C₁₄ H₂₁ Ni₂ N₂ O₁₅, a = 8.330(10) A; α = 90°, b = 27.266(5) A; β = 98.61(10)^o, c = 9.653(10) A; γ = 90° and Z = 4. Both the dimeric complexes were observed to be hexa-coordinated with two different types of donor atoms (nitrogen and oxygen). Details of the synthesis, structures and spectroscopic properties have been discussed.