Introduction: Sulfonamide antibiotics represent an important group of pharmaceutical contaminants that enter aquatic environments due to their widespread use in human and veterinary medicine. Conventional wastewater treatment methods often fail to remove them effectively, which has created the need for advanced oxidation processes such as photocatalysis using titanium dioxide. The efficiency of these processes strongly depends on the composition of the water matrix. Purpose: The aim of this master’s thesis was to investigate the influence of wastewater composition on the photocatalytic degradation of two sulfonamide antibiotics (sulfisoxazole and sulfamethoxazole) and to compare their degradation kinetics in distilled water, synthetic and real wastewaters. Methods: The experiments were conducted in a laboratory photoreactor equipped with ultraviolet A light using titanium dioxide at a concentration of one gram per liter as a photocatalyst. Three water matrices were prepared: distilled water, synthetic wastewater, and real municipal wastewater. The concentrations of the antibiotics were determined using high-performance liquid chromatography with diode array detection. The degradation kinetics were described using a first-order kinetic model, and reaction rate constants and half-lives were calculated. Results: The results showed that photocatalytic degradation was most efficient in synthetic wastewater, where almost complete degradation of sulfamethoxazole and 75 to 80 % removal of sulfisoxazole were achieved after 120 minutes. In distilled water, degradation proceeded more slowly, with approximately 50 % removal of both antibiotics after 120 minutes. The lowest efficiency was observed in real municipal wastewater, where the presence of organic matter, ions, and turbidity significantly inhibited the process, particularly in the case of sulfisoxazole, whose half-life was approximately 407 minutes. Sulfamethoxazole degraded faster than sulfisoxazole in all water matrices. Discussion and Conclusion: The composition of the water matrix significantly affects the efficiency of photocatalytic degradation of sulfonamide antibiotics. The presence of organic matter, inorganic ions, and suspended particles reduces the formation and effectiveness of reactive oxygen species and limits light penetration to the catalyst surface. The results confirm that photocatalysis using titanium dioxide represents a promising method for the removal of sulfonamides; however, optimization of process parameters and potential pre-treatment of wastewater are required for effective application in real systems.
|
