Synthesis of Mesoporous TiO2 Template-Free and Photocatalytic Activity for Azo Dye Degradation

Nanoporous titanium dioxide was prepared by sol-gel technique. To control the surface area, pore size and pore volume of the prepared TiO2, a catalyzed hydrolysis was carried out using different concentrations of silicotungstic acid (SWA) as a template. A fixed molar ratio of H2O/Ti was used. The prepared TiO2 was calcined at 400 or 600oC. Samples were characterized by nitrogen physic-sorption, X-ray powder diffraction (XRD), selected scattered electron diffraction, Raman spectroscopic analysis, Fourier Transform spectroscopy (FTIR), Thermo gravimetric analysis (TGA), Differential scanning calorimetry (DSC), scanning and transmission electron microscopy (SEM and TEM). The photocatalytic activity of the prepared samples was evaluated by the degradation of alizarin yellow under UV light. The results showed that the crystallinity increases as the concentration of SWA decreases. The presence of SWA during the precipitation of TiO2 prevents the formation of rutile phase and suppresses the crystal growth. The results showed also that the surface area increases as the concentration of SWA decreases. The samples prepared using 0.05M SWA and calcined at 600 oC showed a higher activity. Keywords: mesoporous TiO2, photocatalytic degradation, alizarin yellow, azodye

Sol–Gel and Thermally Evaporated Nanostructured Thin ZnO Films for Photocatalytic Degradation of Trichlorophenol

In the present work, thermal evaporation and sol–gel coating techniques were applied to fabricate nanostructured thin ZnO films. The phase structure and surface morphology of the obtained films were investigated by X-ray diffractometer (XRD) and scanning electron microscope (SEM), respectively. The topography and 2D profile of the thin ZnO films prepared by both techniques were studied by optical profiler. The results revealed that the thermally evaporated thin film has a comparatively smoother surface of hexagonal wurtzite structure with grain size 12 nm and 51 m2/g. On the other hand, sol–gel films exhibited rough surface with a strong preferred orientation of 25 nm grain size and 27 m2/g surface area. Following deposition process, the obtained films were applied for the photodegradation of 2,4,6-trichlorophenol (TCP) in water in presence of UV irradiation. The concentrations of TCP and its intermediates produced in the solution during the photodegradation were determined by high performance liquid chromatography (HPLC) at defined irradiation times. Complete decay of TCP and its intermediates was observed after 60 min when the thermal evaporated photocatalyst was applied. However, by operating sol–gel catalyst, the concentration of intermediates initially increased and then remained constant with irradiation time. Although the degradation of TCP followed first-order kinetic for both catalysts, higher photocatalytic activity was exhibited by the thermally evaporated ZnO thin film in comparison with sol–gel one

Platinum 1,10-phenanthroline: Photosensitizer for photocatalytic degradation of 4-chlorophenol

It is more economic to apply photodegradation of organic pollutants in presence of the visible light irradiation (sunlight) than applying more costfull ultraviolet lamps. Hence, platinum 1,10-phenanthroline complex has been prepared and tested as a photosensitizer for photodegrading 4-chlorophenol in water, which has been found almost completely achieved (98.5 %) after three hours of visible irradiation. Nevertheless, irradiation at 364 and 254 nm exhibits lower efficiencies. At visible irradiation, the platinum complex gives the highest activation of singlet state oxygen formation (1O2) compared to 364 and 254 nm irradiation as supported by electron para-magnetic resonance data. On the other hand, the behavior of formation and disappearance of photodegradation intermediates: hydroquinone, benzoquinone, hydroxybenzoquinone, using the platinum complex applying the three current irradiations are found to supports these findings. However, organic acids have accumulated as a function of irradiation time and hence considered to be rate-controlling

Investigation on oil absorption and microstructural properties of polyethylene composites reinforced with post-agricultural waste fillers

Conventional plastic made from polyethylene (PE) is not able to absorb excess oil from the fried food due to its nature to resist water and oil. As a result, oil inside fried food plastic packaging will be accumulated and will affect the freshness and shelf life of the product. To address this issue, polyethylene incorporated post-agricultural waste filler which is rice husk (RH) and rice husk ash (RHA) is produced. Five levels of filler loading which are 10, 15, 20, 25, and 30 in weight percent were incorporated into the PE to produce RH-PE and RHA-PE composites. Tests were performed to evaluate the oil absorption and microstructural properties of the composites. The results showed that the addition of fillers at any loading percentages resulted in significant improvement on the oil absorption of the composites as compared to control sample which is PE. The RH-PE and RHA-PE composites with 25% of fillers were found to possess the best oil absorption property as compared to other compositions. An increase in the loading of fillers would lead to some large agglomeration, high amount of spaces between rice husk and polyethylene and subsequently allow more oil to be absorbed into the composite. It proved that R RH-PE and RHA-PE composites with optimum composition have a great potential to be a good oil absorbent material

An Overview of Recent Development in Composite Catalysts from Porous Materials for Various Reactions and Processes

Catalysts are important to the chemical industry and environmental remediation due to their effective conversion of one chemical into another. Among them, composite catalysts have attracted continuous attention during the past decades. Nowadays, composite catalysts are being used more and more to meet the practical catalytic performance requirements in the chemical industry of high activity, high selectivity and good stability. In this paper, we reviewed our recent work on development of composite catalysts, mainly focusing on the composite catalysts obtained from porous materials such as zeolites, mesoporous materials, carbon nanotubes (CNT), etc. Six types of porous composite catalysts are discussed, including amorphous oxide modified zeolite composite catalysts, zeolite composites prepared by co-crystallization or overgrowth, hierarchical porous catalysts, host-guest porous composites, inorganic and organic mesoporous composite catalysts, and polymer/CNT composite catalysts