Chemical and toxicological evaluation along with unprecedented transformation products during photolysis and heterogeneous photocatalysis of chloramphenicol in different aqueous matrices

The entry of pharmaceuticals into the water cycle from sewage treatment plants is of growing concern because environmental effects are evident at trace levels. Ozonation, UV- and UV/H2O2-treatment were tested as an additional step in waste water treatment because they have been proven to be effective in eliminating aqueous organic contaminants. The pharmaceuticals carbamazepine, ciprofloxacin, diclofenac, metoprolol and sulfamethoxazole as well as the personal care products galaxolide and tonalide were investigated in terms of degradation efficiency and by-product formation in consideration of toxic effects. The substances were largely removed from treatment plant effluent by ozonation, UV- and UV/H2O2-treatment. Transformation products were detected in all tested treatment processes. Accompanying analysis showed no genotoxic, cytotoxic or estrogenic potential for the investigated compounds after oxidative treatment of real waste waters. The results indicate that by-product formation from ozonation and advanced oxidation processes does not have any negative environmental impact.

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Heterogeneous Photocatalysis of Metronidazole in Aquatic Samples

Molecules ◽

10.3390/molecules26247612 ◽

2021 ◽

Vol 26 (24) ◽

pp. 7612

Author(s):

Klaudia Stando ◽

Patrycja Kasprzyk ◽

Ewa Felis ◽

Sylwia Bajkacz

Keyword(s):

Degradation Products ◽

Transformation Products ◽

Heterogeneous Photocatalysis ◽

Bond Breaking ◽

Mass Ratio ◽

Purification Method ◽

Photocatalytic Removal ◽

Catalyst Type ◽

Mineralization Degree ◽

High Degree

Metronidazole (MET) is a commonly detected contaminant in the environment. The compound is classified as poorly biodegradable and highly soluble in water. Heterogeneous photocatalysis is the most promoted water purification method due to the possibility of using sunlight and small amounts of a catalyst needed for the process. The aim of this study was to select conditions for photocatalytic removal of metronidazole from aquatic samples. The effect of catalyst type, mass, and irradiance intensity on the efficiency of metronidazole removal was determined. For this purpose, TiO2, ZnO, ZrO2, WO3, PbS, and their mixtures in a mass ratio of 1:1 were used. In this study, the transformation products formed were identified, and the mineralization degree of compound was determined. The efficiency of metronidazole removal depending on the type of catalyst was in the range of 50–95%. The highest MET conversion (95%) combined with a high degree of mineralization (70.3%) was obtained by using a mixture of 12.5 g TiO2–P25 + PbS (1:1; v/v) and running the process for 60 min at an irradiance of 1000 W m−2. Four MET degradation products were identified by untargeted analysis, formed by the rearrangement of the metronidazole and the C-C bond breaking.

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