Active pharmaceutical ingredients in the aquatic environment are a major global problem today. Year by year, their consumption is increasing and so is their presence in environmental waters. There is a large body of research indicating the potential dangers of these substances to the environment, humans as well as animals. In recent decades, advanced oxidation processes (AOPs) have proven to be an effective method for removing active substances and other pollutants from wastewater. Among the advanced oxidation processes, the TiO2 photocatalysis and ultrafine ozone bubbles show great potential for degradation.
For the master’s thesis research, we collaborated with the Faculty of Chemistry and Chemical Technology of the University of Ljubljana and the Slovenian company Waboost d.o.o. The company is developing an innovative apparatus for increasing the efficiency of pollutant degradation by generating ozone in ultrafine bubbles, while research on photocatalytically active TiO2 is ongoing at the Faculty of Chemistry and Chemical Technology.
We prepared nitrogen-doped TiO2, which is activated by UV light irradiation, selected ten pollutants of environmental concern from different sources and carried out their degradation using photocatalysis and ultrafine bubbles of ozone. For both methods, ultra-high performance liquid chromatography (UHPLC) with a diode array detector (DAD) was used to monitor the degradation efficiency and the concentration of the pollutants at the end of the analysis.
The UHPLC method was validated in the study by a three-day partial validation, where the linearity, accuracy, detection limit and limit of quantification of the method were determined, as well as the reproducibility of the injection of the standards and their stability after 72 hours.
Contaminants were successfully degraded using both photocatalytically active TiO2 thin films and ultrafine ozone bubbles. The introduction of the ultrafine bubbles achieved 100 % degradation for bisphenol A, diclofenac, estradiol, carbamazepine, naproxen, propyphenazone, sulfamethoxazole, tramadol, trimethoprim and valsartan during the 60 minutes of the experiment. 100 % degradation was achieved for nine out of ten analytes already within the first three minutes. In the degradation using the TiO2 photocatalyst, 100 % degradation was achieved for naproxen, tramadol, trimethoprim and valsartan during the 90 minutes of the experiment. For bisphenol A, diclofenac, propyphenazone, sulfamethoxazole and carbamazepine the degradation was 90 % and 71 % for estradiol.
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