Photocatalytic UV-Induced Approach for Discoloration of Bromocresol Purple, Bromothymol Blue Dyes and Their Mixture Using Nix Fe3−xO4/Fe2O3/AC Composites

The nickel ferrite-activated carbon samples NiFe2O4/Activated carbon and NixFe3−xO4/Fe2O3/AC, x = 0.25; 0.5 obtained by co-precipitation followed by thermal treatment in inert atmosphere, were studied for discoloration of Bromocresol Purple (BCP), Bromothymol Blue (BTB) dyes and their mixture as model contaminants under UV-A light. The prepared materials were investigated by XPS, PXRD and XRF analysis, FT-IR spectroscopy, SEM, EDX, BET method and TG analysis. The photocatalyst with composition NixFe3−xO4-AC, x = 1 has demonstrated the highest photocatalytic activity towards discoloration of the BTB in comparison with the others tested materials NixFe3−xO4/Fe2O3/AC, x = 0.25; 0.5. These results can be explained with the smaller particle sizes, the mesoporous structure, the higher degree of crystallinity and higher content of hydroxyl groups. This study proved that the obtained nickel ferrite-activated carbon materials are suitable as photocatalysts for discoloration of the BTB dye. They have demonstrated also relatively high adsorption ability towards BCP dye

DOPING SILVER TO ACTIVATED ZNO TO PROMOTE THE PHOTOCATALYTIC EFFICIENCY FOR AZO DYE DEGRADATION

Various silver doped ZnO activated powders were prepared through an original method of activation. The samples were characterized using XRD analysis, single point BET method, scanning electron microscopy (SEM). The photocatalytic properties of the samples were tested in the reaction of Reactive Black 5 azo dye (model waste water contaminant) oxidative discoloration in a semi-batch reactor. The silver doped samples have higher degree of cristallinity in comparison to the undoped sample and superior photocatalytic performance under UV-A light illumination. Another factor promoting the photocatalytic properties is the increase of the dopant content decreasing the ZnO particle mean size and increasing the specific surface area of the doped samples. The role of silver nanoparticles is to serve as traps for the photoexcited electrons thus preventing recombination and increasing the lifetime of the positively charged holes, acting as oxidation active sites

Porous Texture of CuO Prepared from Copper Oxalate Precursor

The porous texture of CuO obtained from CuC 2 O 4 • 0.5H 2 O as a precursor, as well as the interconnection between the texture of the initial oxalate and that of the copper oxide obtained, has been studied by physisorption, XRD, XPS and SEM methods. The dimensions of the particle aggregates and the crystalline particles were altered as a consequence of the thermal decomposition of CuC 2 O 4 • 0.5H 2 O to CuO, and this led to an increase of ca. 1.5-times in the specific surface of the CuO obtained relative to that of the initial substance. The comparatively non-uniform sizes of the intra-aggregate mesopores in CuC 2 O 4 • 0.5H 2 O were transformed into considerably smaller intra-aggregate mesopores in CuO. A finite increase in the volume of the intra-crystallite pores in CuO was also observed, although this did not change the average size of the intra-crystallite pores in the oxide obtained nor the character of the pore-size distribution with respect to the starting material. In addition, as a result of the thermal decomposition of CuC 2 O 4 • 0.5H 2 O, the mesoporosity of the prepared oxide also developed. However, the CuO component retained the textural type characteristic of the initial CuC 2 O 4 • 0.5H 2 O

PHYSICOCHEMICAL AND PHOTOCATALYTIC INVESTIGATIONS OF MECHANOCHEMICALLY TREATED TIO2-ZNO COMPOSITES

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Ozone decomposition on ZnO catalysts obtained from different precursors

Kinetic investigations for ozone conversion on three different series of zinc oxide catalysts, containing pure ZnO and doped with Mn or Cu one with dopant content less than 1 wt.% were carried out. The different samples were obtained from carbonate, nitrate and acetate precursors. The as prepared catalysts were characterized by AAS, XRD, IR, EPR and BET methods. The mean size of the crystallites determined by XRD data is in the range 27÷68 nm. The presence of Mn2+ and Cu2+ ions into the ZnO matrix was established by EPR. The ozone decomposition was investigated for 30÷75°C temperature range. The zinc carbonate precursor samples show highest activity, while the nitrate precursor ones show lowest activity toward reaction decomposition of ozone in the whole temperature range. At 75°C two of the catalyst, obtained from carbonate precursor - ZnO and CuZnO show 100% conversion

EFFECT OF LA DOPANT ON THE PHOTOCATALYTIC EFFICIENCY OF ACTIVATED ZNO NANOPOWDERS

Activated ZnO powder was obtained by an original patented procedure and doped with 0.5, 1 and 1.5 wt % La to improve the photocatalytic performance. The crystalline structure, surface morphology and specific surface area were investigated by X-ray diffractometer (XRD), scanning electron microscopy (SEM) and single point Brunauer-Emmett-Teller (BET) method. The XRD analysis of the oxide samples illustrates the formation of wurtzite ZnO. Increasing of La concentration results in higher degree crystallinity of the doped ZnO samples. The doped and non-doped ZnO crystallite sizes are in the range of 54÷57nm. Doping with La leads to increase of specific surface area compared to non-doped ZnO. The course of the photocatalytic reaction was followed spectrophotometrically based on the maximum absorbance wavelength of the model pollutant Reactive Black 5 (RB5). The samples doped with 1.5 wt % La exhibited the highest efficiency for the photocatalytic degradation of RB5 under UV illumination due to the higher degree of crystallinity, formation of solid solution and higher specific surface area

PHOTODISCOLORATION OF REACTIVE BLACK 5 DYE USING MECHANOCHEMICALLY ACTIVATED TiO 2 -CeO 2 PHOTOCATALYSTS

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PHOTODISCOLORATION OF REACTIVE BLACK 5 DYE USING MECHANOCHEMICALLY ACTIVATED TIO2-CEO2 PHOTOCATALYSTS

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DISCOLORATION OF REACTIVE DYES IN WASTEWATERS BY OZONATION

Three different reactive dyes - Reactive Blue 19, Reactive Orange 16 and Reactive Red 180 were dissolved in water separately in concentration 0.04g/l as model pollutants for contaminated wastewaters from textile industry. Every wastewater sample was treated by ozone with concentration 2000 ppm for 30 minutes at ambient temperature and the effect of discoloration was traced after 5, 10, 20 and 30 minutes. The highest degree of discoloration was obtained for Reactive Blue 19 model water pollutant dye where 98% discoloration was reached after 5 minutes ozonation and 99% after 30 minutes treatment, while the lowest discoloration was observed for Reactive Orange 16 – 84% after 30 minutes treatment. The discoloration degree for the three sample solutions in the whole time interval was as follows: Reactive Blue 19 > Reactive Red 180 > Reactive Orange 16. In summary it can be concluded than application of ozone treatment for wastewaters, containing different reactive dyes is very effective and practically applicable