Pollution of fresh water poses a problem that has been present since the beginning of Industrial Revolution. Organisation of United Nations estimates that there are currently over one billion people in the world without access to fresh drinking water. A problem unto itself are persistent pollutants which are used in large quantities in various branches of industry. Most notable endocrine-disrupting chemicals that fall into this category are bisphenols, which are known to have a strong effect on physiological processes even in relatively small quantities. In the last years, advanced oxidation processes have emerged as a novel way of removing persistent pollutants from wastewater. A wide array of advanced oxidation processes allows for a high degree of adjustment to the specifications set by the user in wastewater treatment. One of the most useful techniques in this regard is heterogenous photocatalysis in which photocatalitically active TiO2 is used as the catalyst.
During the course of our experimental work, we prepared Au+TiO2 plasmonic catalysts. TiO2 nanoparticles were used as starting material in production of TiO2 nanorods with alkaline hydrothermal synthesis. Supported Au+TiO2 catalysts were produced from TiO2 nanorods and TiO2 nanoparticles in the process of deposition-precipitation. We evaluated physicochemical properties of Au+TiO2 catalysts and their photocatalytic performance upon irradiation with visible light. Furthermore, synthesized materials were used in photocatalytic oxidation reactions of four different bisphenols (bisphenol A, S, AF and F) under visible light. Concentrations of these pollutants during the experiment were monitored with the use of high performance liquid cromatography. Degrees of mineralization of organic pollutants were determined by measuring total organic carbon before and after experiments were conducted. Our research indicates that Au+TiO2 nanorods and Au+TiO2 nanoparticles differ in their physicochemical properties and in their photocatalytic performance under visible light. Presence of gold at the catalyst's surface has a significant impact on its catalytical performance under visible light. Our research also indicates that Au+TiO2 catalysts are suitable for use in degradation of organic pollutants such as bisphenols, although Au+TiO2 nanorods have proven to be a more effective catalyst than Au+TiO2 nanospheres in this regard. When using Au+TiO2 nanorods as the photocatalyst, 95 % of BPF, 80 % of BPA, slightly over 20 % of BPS and slightly under 20 % of BPAF were degraded during two hours of the reaction. Less successful degradation of the latter two pollutants can be attributed to their specific structural elements.
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