With industrial development, more and more chemicals are coming into use, which to a certain extent enter the environment and pollute drinking water and other water sources. In developing countries, the use of chemicals has increased significantly, while environmental concerns are low, making drinking water, rivers, lakes, and the sea extremely polluted in some places. An example of harmful chemicals is hormone disruptors, which increase the risk of infertility, cancer, metabolic and cognitive disorders even in low concentrations. To solve this problem, new effective methods for the removal of pollutants from the environment need to be developed. Advanced oxidation processes are often in use for water treatment since they can nonselectively degrade organic pollutants to H2O, CO2, and inorganic ions. As a part of advanced oxidation processes, heterogeneous photocatalysis is a promising method in which metal (TiO2, Cu2O, ZnO, ZnS) and nonmetal (graphitic carbon nitride) photocatalysts are used.
In the research project, various graphitic carbon nitride photocatalysts operating in visible light were prepared from different starting compounds (dicyandiamide, thiourea and melamine). Optical, surface, structure properties, and reactive oxygen species production effectiveness of prepared catalysts were determined by different characterization methods. Photocatalytic degradation activity was determined by the degradation of bisphenols in a batch reactor. Bisphenol concentrations at certain time intervals were measured by high performance liquid cromatography. To determine the mineralization percentage of different bisphenols total organic carbon was measured in the final and initial solution.
The prepared g-C3N4 photocatalysts showed different optical and surface properties. The production of reactive oxygen species and the percentage of photocatalytic degradation also differed significantly. Photocatalysts made from dicyandiamide and thiourea have more similar properties than the photocatalyst made from melamine. Photocatalyst, made from melamine, has the highest specific surface area and generates more hydroxyl radicals than other catalysts. Since melamine catalyst was most successful at removing bisphenol A from the reaction mixture (54%), we used it to degrade other bisphenols. After 120 minutes 51 % of bisphenol F, 28 % of bisphenol AF, and 8 % of bisphenol S were removed. Catalyst, made from melamine, proved to be useful for BPA and BPF removal, but inefficient for BPAF and BPS removal, as they are more resistant to photocatalytic degradation.
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