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The porous texture of CuO obtained from CuC2O4 • 0.5H2O 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 CuC2O4 • 0.5H2O 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 CuC2O4 • 0.5H2O 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 CuC2O4 • 0.5H2O, the mesoporosity of the prepared oxide also developed. However, the CuO component retained the textural type characteristic of the initial CuC2O4 • 0.5H2O.

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.

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Zinc oxide photocatalysts doped with manganese (0.04-1 at.%) were synthesized via precipitation technique. Their characteristics were studied by Xray diffraction (XRD) and BET analysis. The calculated mean size of the crystallites was in the range of 31-45 nm. Manganese doping of ZnO samples results in slight decrease in crystalline size. Increasing the Mn content in ZnO powders results in a lower photocatalytic activity. The pure ZnO nanopowders decolorate Reactive Black 5 dye under ultraviolet light to almost 92% for 2 h.

Activated ZnO powder has been prepared by procedures involving first its dissolution in nitric acid, then simultaneous treatment by adding NH4OH and CO2 bubbling leading to precipitation as Zn(OH)CO3 (ZH) and further thermal decomposition of ZH at 400 °C. The gas evolution leads to formation of pores and increase in the specific surface area. Chemically activated M/ZnO powders doped with Mn, Co, Ni, Cu, and Ag have been obtained by the impregnation method. The samples have been characterized by ultraviolet-visible (UV-Vis) spectroscopy, diffuse reflectance (DR) UV-Vis, X-ray diffraction (XRD), single point Brunauer-Emmet-Teller (BET), scanning electron microscope (SEM), and X-ray photoelectron spectroscopy (XPS) methods. The experiments have shown that metal-doped activated ZnO powders possess higher photocatalytic activities in oxidative discoloration of model contaminant textile coloring dye Reactive Black 5 in slurry reactor compared to that of the pure ZnO. The XRD and XPS data have shown the presence of defects, nonstoichiometricity implying the formation of solid solutions. Copper-doped (1.5 wt%) activated ZnO (Cu(2+) replaces Zn(2+)) is outstanding in its photocatalytic performance in discoloration of the dye due to the higher specific surface area and improved charge carrier separation.

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.

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