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Advanced catalytic processes for wastewater treatment

We develop nanocrystalline and nanostructured heterogeneous catalysts, preferably based on titanium dioxide, which are used in advanced oxidation processes (such as heterogeneous photocatalytic oxidation, catalytic wet air oxidation and wet peroxide oxidation) for efficient removal of priority organic pollutants from wastewater. Synthesis of catalysts is based on quantitative determination of structure-activity and structure-selectivity relationships. We also perform research regarding the design of advanced reactor systems aimed to conduct these processes.

Catalytic wet air oxidation (CWAO)

The presence of pesticides, pharmaceuticals, hormones, endocrine disruptors (EDCs) as well as personal care products in the outflow of water treatment plants, rivers, drinking water and groundwater increases the concern of the international community and consequently intensifies activities in this field. Biological treatment processes do not always give satisfactory results, because many organic pollutants are either toxic or persistant and therefore not suitable for biological degradation. Therefore, advanced oxidation processes (AOPs), based on chemical oxidation, represent the only option for the elimination of liquid-dissolved organic pollutants, such as pesticides and endocrine disruptors. This group of treatment techniques also includes the process of catalytic wet-air oxidation (CWAO), which is based on the oxidation of organically polluted aqueous solutions and primarily involves the participation of hydroxyl radicals and energy (i.e. heat) in the oxidation reaction steps, leading ultimately to the degradation of pollutants. Complete mineralization of dissolved organic pollutants in water samples can be achieved by conducting the CWAO process in a bubble-column or trickle-bed reactor at high pressures and temperatures. In the Laboratory for Environmental Sciences and Engineering we develop new and economically more efficient catalysts based on titania, the effectiveness of which for the removal of priority organic pollutants from model solutions and real effluents is investigated in a three-phase trickle-bed reactor.

Heterogeneous photocatalytic oxidation

Titanium dioxide (TiO2) is the most widely used semiconductor material, which is due to a variety of its applications in different fields. It is an abundant, cheap and non-toxic material, with a high prospective for addressing environmental concerns. It can mainly be found in three different crystalline forms: anatase, rutile and brookite. Anatase is commonly known as the most active phase and therefore extensively used in a variety of photocatalytic applications. Its high activity is directly connected to prolonged lifetime of charge carriers and spatial charge separation. Efficiency of the photocatalytic process is largely limited by unfavourable electron-hole recombination, so coupling two different types of photoactive semiconductor materials can have a beneficial effect on enhancing charge separation, thus inhibiting rapid recombination of excited electrons with valence band holes. In the Laboratory for Environmental Sciences and Engineering we develop novel and efficient TiO2 nanocomposites consisting of either two or three polymorphs. Photocatalytic activity of synthesized solids is evaluated in advanced oxidation processes (AOPs) by investigating the removal of priority organic pollutants from wastewaters.

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