In the present study, the coupling of adsorption capacity and photocatalytic efficiency of two different industrially produced titania catalysts was investigated and compared. The azo dye Reactive Red 195 was selected as a model compound. The tested catalysts, PK-10 and PK-180, exhibited different adsorption capacities due to their significant difference in their specific surface, but both have proven to be effective photocatalysts for photodegradation of the studied dye. PK-10 exhibited strong adsorption of the studied dye due to its high specific surface area, while the second studied catalyst, PK-180, demonstrated negligible adsorption of Reactive Red 195. The effect of the pH, the concentration of the catalyst and the initial concentration of the dye appear to affect the photocatalytic rate. The effect of the presence of humic acids and inorganic ions was also examined, while the contribution of various reactive species was indirectly evaluated through the addition of various scavengers. To evaluate the extent of mineralisation of the studied dye, total organic carbon (TOC) measurements during the experiment were also conducted. Besides total colour removal, evident reduction of TOC was also achieved using both catalysts.
The presented study is focused on optimization and characterization of a high-alumina refractory aggregate based on natural raw materials—kaolins, claystone, and mullite dust by-product (used to increase the alumina and mullite contents, respectively). In total, four individual formulas with the Al2O3 contents between 45 and 50 wt.% were designed; the samples were subsequently fired, both in a laboratory oven and an industrial tunnel furnace. The effects of repeated firing were examined during industrial pilot tests. Mineral and chemical compositions and microstructures, of both the raw materials and designed aggregates, were thoroughly investigated by the means of X-ray fluorescence spectroscopy, powder X-ray diffraction, and optical and scanning electron microscopies. Porosity, mineral composition, and mullite crystal-size development during the firing process were also studied. Based on the acquired results, the formula with the perspective to be used as a new mullite grog, featuring similar properties as the available commercial products, however, with reduced production expenses, was selected. The quality of grog determines to a large extent the properties of the final product. Hence, optimization of aggregates for specific refractories is of a great importance. The production of engineered aggregates provides the opportunity to utilize industrial by-products.
The kaolinite/TiO 2 composite (60 wt% of TiO 2 ) was prepared by thermal hydrolysis of a raw kaolin suspension in titanyl sulphate and calcined at different temperatures (600, 650 and 700°C) and for different times (1, 2 and 3 h). The obtained samples were characterized by XRPD, N 2 physical adsorption and SEM, and tested for photocatalytic reduction of CO 2 . The different calcination conditions did not influence TiO 2 phase composition, only slightly changed the specific surface area, and significantly affected crystallite size of kaolinite/TiO 2 composite. A higher temperature and longer duration of calcination lead to higher crystallinity of the powder. The photocatalytic results showed that the crystallite size determined the efficiency of kaolinite/TiO 2 photocatalysts.
AbstraktKompozit kaolinit/TiO 2 (60 hm% TiO 2 ) byl připraven termální hydrolýzou suspenze surového kaolinu v síranu titanylu a kalcinován při různých teplotách (600, 650 a 700°C) a po různou dobu (1, 2 a 3 h). Získaný vzorek byl charakterizován pomocí XRPD, N 2 fyzikální adsorpcí a SEM, a testován na fotokatalytickou redukci CO 2 . Rozdíl kalcinačních podmínek neovlivnil složení fáze TiO 2 , pouze se mírně pozměnila specifická povrchová plocha a výrazně byla ovlivněna velikost krystalitu kompozitu kaolinit/TiO 2 . Vyšší teplota a delší doba kalcinace vedly k vyšší krystalitě prášku. Fotokatalytické výsledky ukázaly, že velikost krystality určuje účinnost fotokatalyzítoru kaolinit/TiO 2 .
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