Nanocomposite hydrogel from grafting of acrylamide onto HPMC using sodium montmorillonite nanoclay and removal of crystal violet dye

Hydrogel nanocomposites were synthesized from grafting of acrylamide onto hydroxypropyl methylcellulose using methylenebisacrylamide crosslinker and sodium montmorillonite (Na-MMt) nanoclay. The effect of nanoclay content on the swelling of nanocomposites was investigated and an optimum swelling capacity was obtained at 12.7 wt% of Na-MMt. The effect of salt solutions on the swelling of nanocomposites revealed that the degree of swelling of samples depends only slightly on the salinity. The structure of nanocomposites was characterized by XRD, SEM, FTIR, and TEM techniques. The XRD and TEM results confirmed the exfoliation of Na-MMt nanoclay in nanocomposite matrix. The morphology of the nanocomposites was characterized by SEM technique and according to the results a loose surface was observed. The nanocomposite hydrogels were evaluated to remove cationic crystal violet dye from water. The investigation of the dye adsorption capacity and rate of nanocomposite hydrogels as a function of Na-MMt content revealed that the both adsorption capacity and rate is enhanced as the nanoclay content is increased in nanocomposite composition. The experimental equilibrated adsorption capacity of nanocomposites was analyzed using Freundlich and Langmuir isotherm models. The best fit to the experimental data was obtained with the Langmuir model.     

Development a robust ionic liquid-based dispersive liquid-liquid microextraction against high concentration of salt combined with flame atomic absorption spectrometry using microsample introduction system for preconcentration and determination of cobalt in water and saline samples

A robust ionic liquid-based method for dispersive liquid-liquid microextraction was developed for the determination of cobalt in saline samples. Its robustness was increased by introducing a common ion of the IL into the sample solution. The concentration of cobalt in the settled phase of the ionic liquid was determined by the FAAS using a homemade microsample injection valve. Under the optimized conditions, the calibration graph was linear in the concentration range from 0.4 to 120 ??g L^?1 with the detection limit of 0.1 ??g L^?1. Accuracy was checked against the ISO standard method. The method was successfully applied to the determination of cobalt in water and saline samples.     

Spectrophotometric determination of ternary mixtures of thiamin, riboflavin and pyridoxal in pharmaceutical and human plasma by least-squares support vector machines.

Ternary mixtures of thiamin, riboflavin and pyridoxal have been simultaneously determined in synthetic and real samples by applications of spectrophotometric and least-squares support vector machines. The calibration graphs were linear in the ranges of 1.0 - 20.0, 1.0 - 10.0 and 1.0 - 20.0 microg ml(-1) with detection limits of 0.6, 0.5 and 0.7 microg ml(-1) for thiamin, riboflavin and pyridoxal, respectively. The experimental calibration matrix was designed with 21 mixtures of these chemicals. The concentrations were varied between calibration graph concentrations of vitamins. The simultaneous determination of these vitamin mixtures by using spectrophotometric methods is a difficult problem, due to spectral interferences. The partial least squares (PLS) modeling and least-squares support vector machines were used for the multivariate calibration of the spectrophotometric data. An excellent model was built using LS-SVM, with low prediction errors and superior performance in relation to PLS. The root mean square errors of prediction (RMSEP) for thiamin, riboflavin and pyridoxal with PLS and LS-SVM were 0.6926, 0.3755, 0.4322 and 0.0421, 0.0318, 0.0457, respectively. The proposed method was satisfactorily applied to the rapid simultaneous determination of thiamin, riboflavin and pyridoxal in commercial pharmaceutical preparations and human plasma samples.     

Nanocrystalline magnesium oxide: a novel and efficient catalyst for facile synthesis of 2,4,5-trisubstituted imidazole derivatives

Abstract  

Nanocrystalline magnesium oxide with high specific surface area has been used as a novel and efficient catalyst for an improved and rapid synthesis of biologically active 2,4,5-trisubstituted imidazoles, by three-component, one-pot condensation of 1,2-diketones and aryl aldehydes, in excellent yields under solvent-free and conventional heating conditions. The method has several advantages, for example excellent yields, shorter reaction time, and use of a non-toxic and recyclable catalyst.     

A novel catalytic method for the regeneration of carbonyl compounds from oximes using aluminum nitrate and NaBr as catalyst

<正>A wide variety of aldoximes and ketoximes were regenerated to corresponding carbonyl compounds with Al(NO_3)_3·9H_2O in presence of catalytic amounts of NaBr in CH_2Cl_2 at room temperature.     

Ultrasound-enhanced Green Synthesis of 5,5-Diphenylhydantoin Derivatives Using Symmetrical or Unsymmetrical Benzils

A rapid, highly efficient and mild green synthesis of 5,5‐diphenylhydantoin derivatives was achieved from the reaction of symmetrical or unsymmetrical benzil derivatives with urea in the presence of ethanolic KOH under ultrasound irradiation. This simple method affords 5,5‐diphenylhydantoin derivatives at room temperature in short reaction time with high yield and purity. This study aimed to overcome the limitations and drawbacks of the reported methods such as tedious work‐up, low yield and long reaction time.     

A computational study of water adsorption on boron nitride nanotube

The effect of water molecule adsorption on the surface of (5,0) zigzag boron nitride nanotube was studied by density functional theory calculations. Geometrical optimizations were carried out at the B3LYP/6-31+G* level of theory. Six different configurations of water molecule(s) adsorption process including monomer (1WB and 1WN), dimer (2WB, 2WNN, and 2WBN), and trimer (3WB) clusters were obtained. The strengths of interactions were analyzed by the equilibrium geometries, binding energies, and charge transfer. The natural bonding analysis was also performed to investigate electronic properties. The results reveal that the adsorption of water is more favorable as the water cluster size increases.     

Thiomorpholine-functionalized nanoporous mesopore as a sensing material for Cd2+ carbon paste electrode

A new thiomorpholine-functionalized nanoporous mesopore Mobil Composition of Matter No. 41 (MCM-41), abbreviated as TMMCM-41, was synthesized and applied as a sensing material in construction of a cadmium carbon paste electrode. The electrode composition of 20.1%wt TMMCM-41, 54.0% graphite powder, 25.9% paraffin oil showed the stable potential response to Cd²⁺ ions with the Nernstian slope of 28.6 mV decade^?1 (±1.8 mV decade^?1) over a wide linear concentration range of 10^?6 to 10^?2?mol L^?1 with a detection limit of 6?×?10^?7 mol L^?1. The electrode has fast response time and long-term stability (more than 4 months). The proposed electrode was used to determine the concentration of cadmium in tap water contaminated by this metal and cadmium electroplating waste water samples.