Fotokatalityczna degradacja herbicydów : nowe katalizatory na bazie TiO₂

Over the past few decades a rapid increase in standard of living is observed. Rapid urbanization and development of new technologies, which are focused on the needs of a modern society, influence negatively the environment. The present policy of sustainable development is focused on the principles of rational use of scarce resources and raw materials. New technologies should comply with a number of requirements: efficiency, low costs and a low impact on the environment. Photocatalytic processes are the answer for these requirements. Photocatalysis can be used in many aspects of everyday life, offering self-cleaning surfaces, photo-drugs (e.g. for photodynamic therapy) and even photovoltaic devices. Photocatalytic degradation of pollutants in the presence of inorganic photocatalysts (e.g. TiO₂ or ZnO) is one of the available methods of removing impurities from aqueous and gaseous phases. The main advantage of this process is the lack of wastes and formation of carbon dioxide, water and simple inorganic ions as end- -products. The aim of our work was to develop new TiO₂-based photocatalysts doped with tungsten and molybdenum oxides. A series of materials with different content of the dopants, calcined at various temperatures, was prepared. The photocatalytic activity of the materials was determined following the degradation of two model herbicides: 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T). These compounds are used for the control of weed growth on crop plantations, but in a high dosage they can lead to destruction of the plants. They are readily soluble in water, therefore their use is simple, but brings a great risk to aquatic organisms and people. Photocatalytic degradation of herbicides is the main goal of the 4G-PHOTOCAT project. The efforts are directed towards development of a low-cost photocatalytic paint, that could be used in reactors for groundwater purification. The active ingredient of the paint is a composite material based on TiO₂ modified with other metal oxides.