Preparation and characterization of a clay-polyvinylpyridinium matrix for the removal of bacterial cells from water

Polyvinylpyridinium salts were immobilized onto a clay matrix and were then tested for their antibacterial properties. The clay-polyvinylpyridinium matrix was prepared by the copolymerization of γ-methacryloxypropyltriethoxy silane bonded covalently to clay and 4-vinylpyridine and subsequent quaternization with benzyl halides. Suspension tests for antibacterial properties of the immobilized bactericide against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa demonstrated the high activity of the pyridinium salts that are bonded to the polyacrylate spacer. Advantageously, these insoluble clay-polymer bactericides could be applied without any contamination by the substrate. This revised version was published online in November 2006 with corrections to the Cover Date.     

Nano-sized Spherical MgB2 Superconducting Powder Fabrication Using MHz Range Ultrasonic Spray Pyrolysis (USP) System

We have fabricated 40?C150 nm sized MgB₂ superconducting spherical powders by using a 2.4 MHz ultrasonic spray pyrolysis system and consecutive high temperature heating and powder collection chamber. Various chemical solutions, which contain Mg, B, de-ionized water, acetone and LAPSA in different concentrations and gas atmosphere, were used to obtain MgB₂ superconducting powders. Microstructural, transport and magnetic characterizations of the powders were performed using XRD, SEM-EDX, R-T, M-H analysis and critical current density calculations, which is found in the range of 10⁶ Acm^?2, indicating improved flux pinning properties.     

Monodisperse palladium nanoparticles assembled on graphene oxide with the high catalytic activity and reusability in the dehydrogenation of dimethylamine-borane

Highly effective and stable palladium nanoparticles (Pd NPs) supported on graphene oxide (GO) were synthesized, characterized and applied for dehydrogenation of dimethylamine-borane (DMAB). Monodisperse Pd NPs were synthesized with the ultrasonic reduction method in the presence of oleylamine and GO as support matrices at room temperature. Almost uniformly distributed Pd (0) nanoparticles in size of 3.89 nm were isolated in a reproducible manner by filtering through the reaction mixture. They were characterized by TEM, HRTEM, XRD, Raman, and XPS. It was found that Pd@GO NPs are stable and one of the most active catalysts in the dehydrogenation of DMAB. This catalyst with its turnover frequency of 38.02 h^?1 exhibits one of the good results among all the catalysts prepared in the literature for dehydrogeneration of DMAB. Significant activation parameters of the catalytic dehydrogenation reaction were also calculated, and the activation enthalpy (ΔH^#), activation entropy (ΔS^#) and the apparent activation energy (Ea) were found 16.5 kJ mol^?1, ?179 J mol^?1 K^?1, and 18.6 kJ mol^?1, respectively.     

Adsorptions of high concentration malachite green by two activated carbons having different porous structures

The adsorption of malachite green (MG) from aqueous solution by two different adsorbents (CZn5, PETNa8) were studied. Adsorbents were prepared from pine sawdust and polyethyleneterephatalate (PET) by chemical activation with ZnCl(2) and NaOH, respectively. The adsorption was carried out in a batch system as a function of dye concentration, pH and contact time. Both adsorbents were found to be very effective in removing the dye at high concentration with adsorption percentage in the order of CZn5 > PETNa8. The pH of dye solution in the range of 6-10, was found favorable for the removal of malachite green by using the two adsorbents at high concentrations. Equilibrium times were 120 and 90 min for CZN5 and PETNa8, respectively. Kinetics of removal MG was studied using Lagergren equation and diffusion phenomena was analyzed using Weber and Morris intraparticle diffusion plots. It was also showed that the adsorption isotherm followed Langmuir model.     

Electroinitiated and radiation-induced polymerisation of epoxycyclopentane

Liquid state radiation-induced and electroinitiated polymerisations of epoxycyclopentane (ECP) have been investigated. Dichloromethane and tetrabutylammonium hexafluoro-phosphate were employed as a solvent electrolyte couple. Temperature effects on the rate of electroinitiation were also studied. Apparent activation energy for the electroinitiated polymerisation was calculated from the Arrhenius plot. The propagation of the polymerisation for both methods was found to be through the opening of the epoxy ring, as verified by i.r. and n.m.r. spectra. Both methods of polymerisation yielded tacky, amorphous polymers.     

UV induced reversible chain extension of 1-(2-anthryl)-1-phenylethylene functionalized polyisobutylene

The synthesis of novel 1-(2-anthryl)-1-phenylethylene (APE) di-telechelic polyisobutylenes is described. Utilization of a difunctional cationic initiator and the in situ addition of the non-homopolymerizable APE lead to the formation of di-anthryl telechelic polyisobutylenes. Products were characterized by ¹H NMR spectroscopy and Size Exclusion Chromatography. The polymers were UV irradiated at 365 and 254 nm and the reversible photocycloaddition of anthryl moieties was investigated. The chain extension of di-anthryl telechelic PIBs through photocoupling at 365 nm produced higher molecular weight products from low molecular weight precursors. The effect of precursor polymer concentration on the degree of chain extension was investigated, and intermolecular interactions leading to the formation of tetramers was observed. The photocoupled products were UV irradiated at 254 nm to induce the reversal of photocycloaddition of anthryl groups and to follow the consequent photoscission of polymers.     

Oxidative coupling of methane over NbO (p-type) and Nb2O5 (n-type) semiconductor materials

Oxidative coupling of methane to higher hydrocarbons was investigated using two types of semiconductor catalysts, NbO (p-type) and Nb₂O₅ (n-type) at 1 atm pressure. The ratio of methane partial pressure to oxygen partial pressure was changed from 2 to 112 and the temperature was kept at 1023 K in the experiments conducted in a cofeed mode. The results indicated a strong correlation between C₂₊ selectivity performance and the electronic properties of the catalyst in terms of p-vs. n-type conductivity. The p-type semiconductor catalyst, NbO, had a larger selectivity (e.g. 95.92%) over the n-type Nb₂O₅ catalyst (23.08%) both at the same methane conversion of 0.64%. Catalyst characterization via X-ray diffraction, TGA and reaction studies indicated that NbO was transformed to Nb₂O₅ during the course of the reaction which limits catalyst life.     

SYNTHESIS OF ZSM-5 FROM MODIFIED CLINOPTILOLITE AND ITS CATALYTIC ACTIVITY IN ALKYLATION OF BENZENE TO ETHYLBENZENE

ZSM-5 catalysts were prepared by utilizing clinoptilolite found in Western Anatolia in abundant amounts as a type of natural zeolite. Hydrothermal reaction was conducted with HCl-treated clinoptilolite at 180°C. After characterizing the solid products obtained by this reaction as ZSM-5 by means of XRD, IR, TGA, surface area analyzer, and chemical analysis they were tested as catalysts in benzene alkylation reaction with ethylene leading to ethylbenzene. Catalytic performance of samples prepared in this study was investigated for benzene conversion, ethylbenzene yield, and selectivity. It was found that ZSM-5(A) sample showed performance similar to that of the reference sample (ZSM-5(C)) synthesized by using patented literature information in terms of benzene conversion. When the reaction temperature was increased from 400° to 425°C ethylbenzene yield and selectivity results of ZSM-5(A) sample were improved but coke formation increased. Catalyst test results indicated the possibility of using clinoptilolite as a raw material in the synthesis of ZSM-5 catalyst for alkylation of benzene with ethylene reaction.     

Studies on the applicability of alginate-entrapped Chryseomonas luteola TEM 05 for heavy metal biosorption

Chryseomonas luteola TEM 05 cells were entrapped both in alginate and chitosan coated alginate beads. Biosorption of metal ions on alginate beads was investigated by using a batch stirred system at pH 6.0, 25 degrees C, in initial metal concentration of 1.92 mM of Cr6+, 0.89 mM Cd2+ and 1.69 mM Co2+. Then, a process of competitive biosorption of these metal ions was described and compared to single metal ion adsorption in solution. The apparent equilibrium biosorption was reached within the 180 min of contact for all metals. Although the competitive biosorption capacities of the beads for all metal ions were lower than those of single conditions, Cd2+ biosorption on alginate and alginate-chitosan beads did not change significantly.