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A mixed metal oxide W-TiO2 nanopowder photocatalyst was prepared by using the sol–gel method with a broad range of elemental compositions x = CW/(CW + CTi), including TiO2 and WO3. The material was structurally characterized and evaluated in adsorption and photocatalytic processes by testing its removal capacity of a representative pollutant methylene blue (MB) in aqueous solutions and under UV-A and sunlight illuminations. The nanopowders appeared to be more effective adsorbents than pure TiO2 and WO3 materials, showing a maximum at 15 mol% W, which was set as the tungsten solubility limit in anatase titania. At the same time, the photocatalytic decomposition of MB peaked at 2 mol% W. The examination of different compositions showed that the most effective MB removal took place at 15 mol% W, which was attributed to the combined action of adsorption and heterogeneous photocatalysis. Moreover, MB decomposition under sunlight was stronger than under UV-A, suggesting photocatalyst activation by visible light. The pollutant removal efficiency of the material with 15 mol% W was enhanced by a factor of ~10 compared to pure TiO2 at the beginning of the process, which shows its high potential for use in depollution processes in emergency cases of a great pollutant leak. As a result, a Wx=0.15-TiO2 catalyst could be of high interest for wastewater purification in industrial plants. [ABSTRACT FROM AUTHOR]

In emergency, to produce safe water, that is "potable water free from harmful microorganisms and substances even if it may have colour, odour or taste problem due to dissolved minerals", applied methods should be immediately available to treat contaminated water, to reach at least a microbiological pollution in terms of bacteria concentration is maximum 108 UFC/mL and a maximum concentration of As and COD are 0.1 mg/L and 20 mg/L, respectively. In this work, the treatment of contaminated water to use in environmental and sanitary emergency is performed by the production and employment of proper nanomaterials produced locally. The development of a novel equipment capable to produce quickly and continuously these specific nanomaterials is necessary. Therefore, it was suggested to perform continuous production of the materials by means of process intensification techniques such as the spinning disk reactor (SDR) or the T-mixer reactor (TMR), respectively. Both equipment performed well in producing the required nanomaterials. Concerning the efficiency of the produced materials to lead to safe water in case of emergency, three main parameters were considered: organic matter degradation, heavy metal elimination and anti-bacterial properties. The final results showed that the produced materials are capable to guarantee the required treatment, and it is suggested to use an SDR to produce ferromagnetic core silica shell Al2O3 and Zr/TiO2 coated nanoparticles; the first capable to remove 59.6% of the organic matter, 59.5% of heavy metals and more than 99% of bacteria after 24h. Finally, the nanomaterial can be removed with ease from the water by magnets at 99.1%. This appears to be very good in terms of ease of the emergency handling. Nowadays, the adopted procedure concerns only bacteria and coarse material removal, performed by addition of toxic chlorine. Since the bacteria content is not known, this requires time lasting "trial & error" procedures to adjust the right amount of added chlorine, since it should be sufficient to deactivate 99% of the bacteria but should not exceed specific residual concentration values due to high toxicity. The new approach suggested in this work permits the immediate use of nanomaterials for contaminated water treatment in emergency to a safe one. [ABSTRACT FROM AUTHOR]

The nucleation-growth of titanium oxo-alkoxy (TOA) nanoparticles was studied in n-propanol and isopropanol solvents. A common feature is quasi-instantaneous appearance of stable clusters with the hydrodynamic radius 1.6 nm, which form nanoparticles aggregated during the induction period. In contrast to clusters, the nanoparticle size and growth kinetics were affected by solvent: their size was 3.8 nm in n-propanol and 5.2 nm in isopropanol and the growth kinetics in isopropanol was significantly faster. The results suggest that the stability of the growing TOA units decreases with an increase of size, supporting the hierarchical model of the sol-gel growth. [ABSTRACT FROM AUTHOR]