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

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

Ozone Decomposition on the Surface of Metal Oxide Catalyst

The catalytic decomposition of ozone to molecular oxygen over catalytic mixture containing manganese, copper and nickel oxides was investigated in the present work. The catalytic activity was evaluated on the basis of the decomposition coefficient which is proportional to ozone decomposition rate, and it has been already used in other studies for catalytic activity estimation. The reaction was studied in the presence of thermally modified catalytic samples operating at different temperatures and ozone flow rates. The catalyst changes were followed by kinetic methods, surface measurements, temperature programmed reduction and IR-spectroscopy. The phase composition of the metal oxide catalyst was determined by X-ray diffraction. The catalyst mixture has shown high activity in ozone decomposition at wet and dry O3/O2 gas mixtures. The mechanism of catalytic ozone degradation was suggested

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