Modified Magnetite Nanoparticles for Hexavalent Chromium Removal from Water

Water treatment is an important concern of human societies. Using magnetic nanoparticles as adsorbents for metal removal has been greatly considered due to their particular characteristics such as small sizes, high surface area to volume ratios, and good magnetic properties. In the present study, a modification was implemented in magnetite particles by functionalized carbon nanotubes and carboxylic groups to enhance the performance of magnetite particles in removing hexavalent chromium from water using the adsorption method. The applicability of the nanoadsorbent and magnetic nanoparticles was compared based on adsorption factors affecting the chromium removal including pH, contact time, pollutant concentration, and the adsorbent amount. Properties of the nanocomposites were analyzed by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The results show that the highest percentage of Cr (VI) removal for both adsorbents was under acidic ambient conditions and lasted less than 45 minutes. The study of Langmuir, Freundlich, and Temkin isotherms in the prediction of adsorption behavior revealed that the Langmuir model better fitted the adsorption equilibrium data. The kinetic analysis of pseudo-first and second-order equations showed that the pseudo-second-order equation was more suitable for describing the kinetic behavior of data. Moreover, the obtained nanocomposite had a better performance in Cr (VI) removal from water in comparison to magnetite nanoparticles.     

Synthesis of 2-aroylfuran and novel 3,5-diaroyl-4-arylisoxazole derivatives by ring contraction of pyrylium salts

Research on Chemical Intermediates - Ring contraction of 2,4,6-triarylpyrylium perchlorates by use of sodium nitrite mediated by ionic liquid has been used as a new, direct, and environmentally...     

Ferrocene‐tagged ionic liquid stabilized on silica‐coated magnetic nanoparticles: Efficient catalyst for the synthesis of 2‐amino‐3‐cyano‐4H‐pyran derivatives under solvent‐free conditions

An advanced novel magnetic ionic liquid based on imidazolium tagged with ferrocene, a supported ionic liquid, is introduced as a recyclable heterogeneous catalyst. Catalytic activity of the novel nanocatalyst was investigated in one‐pot three‐component reactions of various aldehydes, malononitrile and 2‐naphthol for the facile synthesis of 2‐amino‐3‐cyano‐4H‐pyran derivatives under solvent‐free conditions without additional co‐catalyst or additive in air. For this purpose, we firstly synthesized and investigated 1‐(4‐ferrocenylbutyl)‐3‐methylimidazolium acetate, [FcBuMeIm][OAc], as a novel basic ferrocene‐tagged ionic liquid. This ferrocene‐tagged ionic liquid was then linked to silica‐coated nano‐Fe₃O₄ to afford a novel heterogeneous magnetic nanocatalyst, namely [Fe₃O₄@SiO₂@Im‐Fc][OAc]. The synthesized novel catalyst was characterized using ¹H NMR, ¹³C NMR, Fourier transform infrared and energy‐dispersive X‐ray spectroscopies, X‐ray diffraction, and transmission and field emission scanning electron microscopies. Combination of some unique characteristics of ferrocene and the supported ionic liquid developed the catalytic activity in a simple, efficient, green and eco‐friendly protocol. The catalyst could be reused several times without loss of activity.     

Silver nanoparticles modified with thiomalic acid as a colorimetric probe for determination of cystamine

Microchimica Acta - The authors describe a colorimetric method for highly selective determination of cystamine using silver nanoparticles capped with thiomalic acid (TMA-AgNPs). The TMA-AgNPs...     

Some results in BL ‐algebras

We define the set of double complemented elements in BL‐algebras and state and prove some theorems which determines properties of these sets. We introduce the notion of an almost top element and study the properties of these elements (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Equilibrium modeling of xylene adsorption on molecular sieves

The separation of xylene isomers is an important application in separation processes that is based on their adsorption properties on different adsorbents. In this work, the Price and Danner method was employed with a neural network to investigate the adsorption behavior of binary systems of p-xylene/m-xylene, p-diethyl benzene/m-xylene, and p-diethyl benzene/p-xylene and the ternary system of p-diethyl benzene/m-xylene/p-xylene at 130 and 175 °C. The Redlich–Kister, Wilson, and NRTL models were used to determine the activity coefficients in the adsorbed phase. Comparison with experimental data from the literature indicated that the proposed thermodynamic model would best determine surface excess when it is used along with the Redlich–Kister activity coefficient model.     

Design and Synthesis of Some Novel Oxiconazole‐Like Carboacyclic Nucleoside Analogues,as Potential Chemotherapeutic Agents

The syntheses of some novel carboacyclic nucleosides, 17a – 17o , containing oxiconazole‐like scaffolds, are described (Schemes 1–3). In this series of carboacyclic nucleosides, pyrimidine as well as purine and other imidazole derivatives were employed as an imidazole successor in oxiconazole. These compounds could be prepared in good yields by using two different strategies (Schemes 1 and 2). Due to Scheme 1, the N‐coupling of nucleobases with 2‐bromoacetophenones was attained for 18a – 18e , and their subsequent oximation affording 19a – 19e and finally O‐alkylation with diverse alkylating sources resulted in the products 17a – 17g, 17n , and 17o . In Scheme 2, use of 2‐bromoacetophenone oximes 20 , followed by N‐coupling of nucleobases, provided 19f – 19j whose final O‐alkylation produced 17h – 17m (Scheme 2). For the rational interpretation of the dominant formation of (E)‐oxime ethers rather than (Z)‐oxime isomers, PM3 semiempirical quantum‐mechanic calculations were discussed and the calculations indicated a lower heat of formation for (E)‐isomers.     

Sensitive,Fast, Solution‐Processed Ultraviolet Detectors Based on Passivated Zinc Oxide Nanorods

Solution‐processed ultraviolet photodetectors based on passivated and unpassivated zinc oxide (ZnO) nanorods, in which the ZnO nanoparticles are synthesized by a hydrothermal method, are demonstrated and characterized. Photoconductive photodetectors fabricated using simple solution processing have recently been shown to exhibit high gains and outstanding sensitivities. One ostensible disadvantage of exploiting photoconductive gain is that the temporal response is limited by the release of carriers from trap states. Herein, specific chemical species are introduced onto the surfaces of ZnO nanoparticles to produce desired trap states with a carefully selected lifetime. Compared with conventional photodetectors based on ZnO nanoparticles, the proposed UV photodetectors have much higher photoresponses and faster response times in the UV region. The photoconductive gain of the fabricated photodetectors varies from 26.83 to 2.32×10² for passivated samples, which indicates high gain. The best temporal response for the fabricated detectors is 34 ms rise time and 132 ms decay time for ZnO nanoparticles passivated by hexamethylenetetramine.     

Multiple Positive Solutions for Semilinear Elliptic Equations Involving Subcritical Nonlinearities in RN

In this paper, we study how the shape of the graph of a（z） affects on the number of positive solutions of -△v＋μb（z）v=a（z）vp-1＋λh（z）vq-1,inRN.（0.1） We prove for large enough λ,μ〉 0, there exist at least k＋ 1 positive solutions of the this semilinear elliptic equations where 1 ≤ q 〈 2 〈 p 〈 2＊ = 2N/（N-2） forN ≥ 3.     

A conductometric study of complexation reaction between dibenzo-24-crown-8 with yttrium cation in some binary mixed non-aqueous solvents

The complexation reaction of macrocyclic ligand, dibenzo-24-crown-8 (DB24C8) with Y⁺³ cation was studied in some binary mixtures of methanol (MeOH), ethanol (EtOH), acetonitrile (AN) and tetrahydrofuran (THF) with dimethylformamide (DMF) at different temperatures using the conductometric method. The conductance data show that in all solvent systems, the stoichiometry of the complex formed between DB24C8 and Y⁺³ cation is 1:1 (ML). The stability order of (DB24C8.Y)⁺³ complex in pure non-aqueous solvents was found to be: AN > EtOH > MeOH > DMF. A non-linear behaviour was observed for changes of log K_f of (DB24C8.Y)⁺³ complex versus the composition of the binary mixed solvents, which was explained in terms of solvent–solvent interactions and also the heteroselective solvation of the species involved in the complexation reaction. The obtained results show that the stability of (DB24C8.Y)⁺³ complex is sensitive to the mixed solvents composition. The values of thermodynamic parameters (?H°_c and ?S°_c) for formation of (DB24C8.Y)⁺³ complex were obtained from temperature dependence of the stability constant using the van’t Hoff plots. The results show that in most cases, the (DB24C8.Y)⁺³ complex is enthalpy destabilized but entropy stabilized and the values and also the sign of thermodynamic parameters are influenced by the nature and composition of the mixed solvents.