Kinetics and thermodynamics of uranium ion adsorption from waste solution using Amberjet 1200 H as cation exchanger

The present work deals with the adsorption of uranium from a nitric acid waste solution using the cation exchange resin Amberjet 1200 H (AHR) . Batch experiments were performed in order to assess the performance of AHR in uranium adsorption. The influences of pH, contact time, initial uranium concentration and temperature have been enhanced. The physical parameters including the adsorption kinetics, the isotherm models and the thermodynamic data have also been determined to determine the nature of the uranium adsorption by AHR. The studied resin has been agreed with both the pseudo second order reaction and Langmuir isotherm.     

In situ crystallization of ZnAl2O4/ZnO nanocomposite on alumina granule for photocatalytic purification of wastewater

Research on Chemical Intermediates - ZnAl2O4/ZnO nanocomposites with different ZnO (20, 30, and 40 mol%) concentrations and coated samples on supports were successfully prepared through...     

Optimization and sensitivity analysis of magneto-hydrodynamic natural convection nanofluid flow inside a square enclosure using response surface methodology

This article studies buoyancy-driven natural convection of a nanofluid affected by a magnetic field within a square enclosure with an individual conductive pin fin. The effects of electromagnetic forces, thermal conductivity, and inclination angle of pin fin were investigated using non-dimensional parameters. An extensive sensitivity analysis was conducted seeking an optimal heat transfer setting. The novelty of this work lies in including different contributing factors in heat transfer analysis, rigorous analysis of design parameters, and comprehensive mathematical analysis of solution domain for optimization. Results showed that magnetic strength diminished the heat transfer efficacy, while higher relative thermal conductivity of pin fin improved it. Based on the problem settings, we also obtained the relative conductivity value in which the heat transfer is optimal. Higher sensitivity of heat transfer was, though, noticed for both magnetic strength and fin thermal conductivity in comparison to fin inclination angle. Further studies, specifically with realistic geometrical configurations and heat transfer settings, are urged to translate current findings to industrial applications.

     

MWCNTs@NHBut/PTA: New efficient solid acid catalyst for solvent free synthesis of benzochromenopyrimidines

In this study, a novel and eco‐friendly synthesis of benzochromenopyrimidines catalyzed by phosphotugstic acid immobilized on aminated multiwalled carbon nanotubes (MWCNTs@NHBut/PTA) is reported. New solid acid catalyst was prepared through a simple process with good percentage of organo metallic groups and characterized with FTIR, TEM, SEM, EDX and TGA techniques. Reusable catalytic system provides a convenient, safe and green pathway to generate a variety of benzochromenopyrimidines under mild conditions.     

Ag3[PMo12O40]: An efficient and green catalyst for the synthesis of highly functionalized pyran‐annulated heterocycles via multicomponent reaction

A facile, efficient and eco‐friendly catalytic protocol was developed for the synthesis of medicinally important pyran‐annulated heterocycles via multicomponent reaction (MCR). Cyclocondensation of differently substituted aromatic aldehydes, malononitrile/ethyl cyanoacetate and various β‐dicarbonyl compounds in the presence of Ag₃[PMo₁₂O₄₀]?nH₂O as heterogeneous catalyst, in EtOH–H₂O, afforded diverse pyran‐fused chromene analogues. The merits observed for this approach were it being conducted via MCR, using commercially available or easily accessible starting materials in the presence of a green and easily separable heterogeneous and reusable catalyst, and affording high yields of desired products in very short reaction times with high purity in one‐pot fashion, thus providing a superior alternative approach for the synthesis of pyran‐annulated heterocycles.     

Thermal and electrical conductivity properties of some CrIII, MnII and UO 2 II amino alcohol complexes

Cr^III, Mn^II and UO₂ ^II amino alcohol complexes were prepared and analyzed. The IR spectra proved that the ligation occurs via oxygen and nitrogen atoms. The nujol mull electronic absorption spectra joined with the room temperature magnetic moment values proved that the complexes are of O_h geometry. The thermal behaviour of the complexes was studied by DTA and TG techniques. The mechanism of the decomposition was suggested. The thermodynamic parameters of the decomposition were evaluated and discussed. The entropy of activation changes, S*, showed that the transition states are more ordered than the reacting complexes. The D.C. electrical conductivity measurements of Cr- and Mn-amino alcohol complexes are of semiconductor behaviour. Empirical equations were deduced for the conduction of the investigated complexes.This revised version was published online in November 2005 with corrections to the Cover Date.     

Organoplatinum(IV) tris-chelate complexes, each having a cyclic metallacarbonate ring: synthesis, characterization and kinetic studies of the formation

The complexes [Pt[(CH2)4](NN)], 1a (NN = 2,2'-bipyridine) and 1b (NN = 1,10-phenanthroline) react with 2,3-epoxypropylphenyl ether in the presence of CO2 to give tris-chelate platina(IV)cyclopentane complexes characterized by 1H and 13C NMR spectroscopy as [Pt[(CH2)4](CH2CHCH2OPhOCO2)(NN)], 2. The reactions proceed by the SN2 mechanism and the rates were independent of concentration of CO2. It is demonstrated that for 1a, the reaction proceeds 2.32 times faster than the similar reaction in which the dimethyl analog, [PtMe2(2,2'-bipyridine)], is used. The analog tris-chelate complex [Pt[(CH2)4](CH2CHPhOCO2)(phen)], 3a, was similarly synthesized.     

An optode membrane for determination of gold using a simple light-emitting diode-based device

Abstract  

A selective optode based on immobilization of 5-(p-dimethylaminobenzylidene)rhodanine on a triacetylcellulose membrane was developed for quantitative determination of Au(III). The determination procedure was performed using a simple light-emitting diode (LED)-based device as a new effort to overcome low reproducibility and repeatability problems which usually accompany optode-based determinations. The results obtained were compared with those of conventional spectrophotometric methods. The response characteristics of the sensor including dynamic range, reproducibility, response time, and lifetime are discussed in detail. This sensor was used for the determination of Au(III) in ore and electroplating liquid effluent samples with satisfactory results in comparison with flame atomic absorption spectroscopy as standard method. Under the optimum conditions, the calibration plot was linear in the concentration range of 0.3–6.0 μg cm⁻³. The relative standard deviations for five replicate determinations of 1.0 μg cm⁻³ Au(III) and the corresponding limits of detection were 1.76% and 0.12 μg cm⁻³, respectively.