Heterogeneous photocatalytic degradation of 4-chlorophenol by immobilization of cobalt tetrasulphophthalocyanine onto MCM-41

The photocatalytic activity of cobalt tetrasulphophthalocyanine immobilized onto MCM-41 was investigated for photocatalytic degradation of 4-chlorophenol (4-CP) in aqueous solutions. Immobilization of cobalt tetrasulphophthalocyanine complex to the walls of MCM-41 was performed by pre-anchorage of 3-(aminopropyl)-triethoxysilane (APTES) onto MCM-41 via post-synthesis method. X-ray diffraction, nitrogen physisorption, diffuse reflectance spectroscopy, energy-dispersive X-ray and FT-IR methods were used to characterize the product. Photocatalytic efficiency of the prepared photocatalyst for degradation of 4-CP was tested under illumination of UV-A and visible light. The reaction intermediates were identified by gas chromatography-mass spectrometry (GC-MS) technique.     

The Acute Toxicity of SiO2 and Fe3O4 Nano-particles on Daphnia magna

Silicon - SiO2 nano-particles are applied in different industries such as ceramic producing, glass making, cosmetic products, medicines, magnetic mixtures, heat and electric insulators and glazing...     

Thermogravimetric Analysis of a Cellulosic Fabric Incorporated by Synthetic Ammonium Magnesium Phosphate as a Flame-Retardant

We have investigated the effect of synthetic struvite (MgNH₄PO₄·6H₂o) on the flammability of a cellulosic fabric. It was synthesized by means of the multiple-bath method and deposited onto a cotton fabric. Its uniformity was ensured by means of squeeze rolls, obtaining the optimum effective add-on value of ammonium magnesium phosphate to impart flame retardancy to cotton fabric in the range of around 12 g anhydrous salt per 100 g fabric. A thermogravimetric analysis of pure cotton, treated cotton, and the salt was accomplished, and their thermograms were compared and commented upon. The results obtained fortified the chemical theory expressing the promotion of the formation of solid char rather than the formation of volatile pyrolysis products, during the fulfillment of thermal decomposition of the cellulosic substrate.     

Direct determination of aluminium in foods and pharmaceutical preparations by potentiometry using an AlMCM-41 modified polymeric membrane sensor

A potentiometric aluminium sensor, based on the use AlMCM-41 as a neutral carrier, in poly(vinyl chloride) (PVC) matrix, is reported. The sensor exhibits significantly enhanced selectivity toward Al³⁺ ions over the concentration range 1.0 × 10⁻⁷ to 1.0 × 10⁻¹ M with a detection limit of 8.6 × 10⁻⁸ M and a Nernstian slope of 19.5 ± 0.4 mV/decade of activity. The best performance was obtained with membrane composition 30% poly(vinyl chloride), 67% acetophenone, 3% ionophore and 2 mL tetrahydrofuran. Fast and stable response, good reproducibility and long-term stability are demonstrated. The response time of the sensor is ∼10 s and membrane could be used over a period of 3 months without any considerable divergence in potentials. Selectivity coefficients were determined by matched potential method (MPM). The AlMCM-41-based sensor is suitable for use in aqueous solution of pH 3-6. The standard electrode potentials were determined at different temperatures and used to calculate the isothermal coefficient of the electrode. It was used to determine Al³⁺ in drugs and food products.     

Ethanol Gas Sensor Based on Pure and La-Doped Bismuth Vanadate

Bismuth vanadate (BiVO₄) and lanthanum-doped bismuth vanadate (La-doped BiVO₄) were prepared via the precipitation method. Their films were produced by simple drop-coating of the initial solutions over gold electrodes, which were coated over a glass substrate. The structural properties of BiVO₄ and La-doped BiVO₄ samples were studied using x-ray diffractometer, diffuse reflectance spectroscopy, scanning electron microscopy, atomic force microscopy, and compositional analysis. A chamber was designed to install the sensing device and also controllable tools for gas flow rate and temperature. Changes in the resistance of the prepared layers were recorded during exposure to various amounts of ethanol vapor at different temperatures. Both BiVO₄ and La-doped BiVO₄ layers showed measurable responses in the form of resistance drop (increased conductivity). The higher temperatures up to 450 °C led to stronger signals. The layer containing lanthanum showed signals with shorter recovery times. Introduction of lanthanum caused smaller crystallite sizes in addition to the formation of tetragonal phase of BiVO₄. Presence of lanthanum increased the amounts of grain boundaries, magnitude of the response, and sensitivity. Sensitivity of La-doped BiVO₄ was almost twice that of the BiVO₄ at concentrations of 150–500 ppm of ethanol. Also, the correlation of the response as a function of concentration of ethanol in gas phase was exploited, and two different linear ranges were observed for the lower and higher concentrations.     

Preparation and characterization of CoxMnmCrnNikFe3-(x+m+n+k)O4 ferrites and optimization of their structural and magnetic properties by Taguchi experimental design

Powders of spinel type ferrite, Co_xMn_mCr_nNi_kFe_3-(x+m+n+k)O₄, have been prepared by a coprecipitation method. The spinel type ferrite was obtained by pre-sintering at 200–1000 °C for 30–120 min in air. In order to optimize the conditions to prepare ferrites of the highest crystallinity, factors such as metal content, temperature and time of reaction, temperature and time of pre-sintering and concentration of NaOH were considered and optimized with Taguchi experimental design and regression analysis. Crystallinity was investigated by XRD analysis. Variation of crystallinity, the average size of crystallites, lattice constant, density and the initial permeability were studied against Mn, Cr and Ni contents. Characterization studies were made on the basis of IR, TG, UV-vis, EDX-SEM, XRF, AAS, XRD, and BET. It was found that the average size of crystallites is decreased when the crystallinity and initial permeability are increased. Some of the results obtained for the final samples were as follows: The X-ray density was 5.34 g cm^-3, the lattice constant, a=0.83662 nm, the average size of crystallites was 87.9 nm, the BET surface area was 1.4 m²g^-1 and the initial permeability was 36.14.     

Photocatalytic self-cleaning properties of cellulosic fibers modified by nano-sized zinc oxide

Nano-sized zinc oxide was synthesized and deposited onto cellulosic fibers using the sol-gel process at ambient temperature. The prepared materials were characterized using several techniques including scanning electron microscopy, transmission electron microscopy, diffuse reflectance spectroscopy, X-ray diffraction and thermogravimetric analysis. X-ray diffraction studies of the ZnO-coated fiber indicate formation of the hexagonal crystal phase which was satisfactory crystallized on the fiber surface. The electron micrographs show formation of zinc oxide nanoparticles within 10-15 nm in size which have been homogeneously dispersed on the fiber surface. The prepared materials show significant photocatalytic self-cleaning activity, which was monitored by diffuse reflectance spectroscopy. The photoactivity was studied upon measuring the photodegradation of methylene blue and eosin yellowish under UV-Vis irradiation. The photocatalytic activity of the treated fabrics was fully maintained performing several cycles of photodegradation.     

Photoactive behavior of polyacrylonitrile fibers based on silver and zirconium co‐doped titania nanocomposites: Synthesis,characterization, and comparative study of solid‐phase photocatalytic self‐cleaning

Silver and zirconium co‐doped and mono‐doped titania nanocomposites were synthesized and deposited onto polyacrylonitrile fibers via sol–gel dip‐coating method. The resulted coated‐fibers were characterized by X‐ray diffraction (XRD), scanning electron microscopy, energy dispersive spectroscopy, transmission electron microscopy, diffuse reflectance spectroscopy, thermogravimetric analysis, and BET surface area measurement. Photocatalytic activity of the TiO₂‐coated and TiO₂‐doped coated fibers were determined by photomineralization of methylene blue and Eosin Y under UV–vis light. The progress of photodegradation of dyes was monitored by diffuse reflectance spectroscopy. The XRD results of samples indicate that the TiO₂, Ag‐TiO₂, Zr‐TiO₂, and Ag‐Zr‐TiO₂ consist of anatase phase. All samples demonstrated photo‐assisted self‐cleaning properties when exposed to UV–vis irradiation. Evaluated by decomposing dyes, photocatalytic activity of Ag–Zr co‐doped TiO₂ coated fiber was obviously higher than that of pure TiO₂ and mono‐doped TiO₂. Our results showed that the synergistic action between the silver and zirconium species in the Ag‐Zr TiO₂ nanocomposite is due to both the structural and electronic properties of the photoactive anatase phase. These results clearly indicate that modification of semiconductor photocatalyst by co‐doping process is an effective method for increasing the photocatalytic activity. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Characterization and Photocatalytic Activities of Mesoporous Silica Containing BiVO4 or La‐BiVO4

Pure monoclinic BiVO₄, La‐doped BiVO₄ catalysts, and MCM‐41 samples containing BiVO₄ and La‐doped BiVO₄ were prepared via precipitation. An improved photocatalytic activity was observed in the degradation of 2,4,6‐trichlorophenol using La‐doped samples. With higher amounts of La, a partial tetragonal crystalline phase of bismuth vanadate was found. The pure and La‐doped BiVO₄ sample were loaded onto the mesoporous silica MCM‐41. Enhanced catalytic activity was achieved in comparison with those not being loaded onto MCM‐41. The lowered band gap following the introduction of La ions and also formation of higher amounts of surface complexes with pollutant molecules are the main reasons of the improved catalytic activity. A comparison of the extent of different chlorophenols toward degradation over the prepared catalysts revealed that under current experimental conditions the samples with more chloride groups suffer higher degradation.     

Semiconductor‐assisted self‐cleaning polymeric fibers based on zinc oxide nanoparticles

Self‐cleaning polymeric fibers have been successfully prepared by depositing ZnO nanoparticle onto wool and polyacrylonitrile (PAN) fibers with good compatibility and significant photocatalytic self‐cleaning activity using the sol‐gel process at ambient temperature. scanning electron microscopy, energy dispersive spectroscopy, transmission electron microscopy, diffuse reflectance spectroscopy, X‐ray diffraction, Brunauer‐Emmett‐Teller surface area analysis, and thermogravimetric analysis have been adopted as the characterization techniques. Transmission electron microscopy studies revealed presence of zinc oxide nanoparticles with 10–15 nm in size. Brunauer‐Emmett‐Teller measurement showed surface area of 48 m²/g for the ZnO nanoparticles. Photocatalytic activity of the self‐cleaning materials were tested by measuring the photo‐assisted degradation of methylene blue (MB) and eosin yellowish (EY) under ultraviolet‐visible illumination. The results indicate that both of the ZnO‐coated polyacrylonitrile and ZnO‐coated wool fibers acquire photocatalytic activity toward dyes degradation. The photocatalytic activity of the treated fibers is maintained upon several numbers of photodegradation cycles. This facile and cheap preparation technique can be also applied to new polymeric fabrics to produce self‐cleaning materials for industrial application. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011