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Lincomycin belongs to the antibiotics commonly used in veterinary medicine. Its residues are easily spread in the environment because of its physicochemical properties, including resistance to biodegradation and good solubility in water. One of the effective methods for the removal of lincomycin from wastewater is the photocatalytic process, but it is not widely used due to the price of photocatalysts. The aim of this work was to compare the photocatalytic efficiency and the mechanism of lincomycin degradation initiated by UVa radiation in the presence of TiO2-P25 and ZnO, as well as in the presence of industrial pigments commonly used in construction and containing TiO2. Lincomycin was found to undergo efficient photocatalytic degradation in the presence of a commercial TiO2-P25 photocatalyst, industrial pigments containing only anatase, and in the presence of ZnO. On the contrary, industrial pigments containing only rutile or a mixture of rutile and anatase practically did not show any photocatalytic activity. The composition of the solutions after the degradation of lincomycin in the presence of TiO2-P25 and ZnO differed significantly. Most of the identified organic degradation products contained conserved pharmacophores, and some of them could have been highly ecotoxic. [ABSTRACT FROM AUTHOR]

Sulfonamides can be effectively removed from wastewater through a photocatalytic process. However, the mineralization achieved by this method is a long-term and expensive process. The effect of shortening the photocatalytic process is the partial degradation and formation of intermediates. The purpose of this study was to evaluate the sensitivity and transformation of photocatalytic reaction intermediates in aerobic biological processes. Sulfadiazine and sulfamethoxazole solutions were used in the study, which were irradiated in the presence of a TiO2-P25 catalyst. The resulting solutions were then aerated after the addition of river water or activated sludge suspension from a commercial wastewater treatment plant. The reaction kinetics were determined and fifteen products of photocatalytic degradation of sulfonamides were identified. Most of these products were further transformed in the presence of activated sludge suspension or in water taken from the river. They may have been decomposed into other organic and inorganic compounds. The formation of biologically inactive acyl derivatives was observed in the biological process. However, compounds that are more toxic to aquatic organisms than the initial drugs can also be formed. After 28 days, the sulfamethoxazole concentration in the presence of activated sludge was reduced by 66 ± 7%. Sulfadiazine was practically non-biodegradable under the conditions used. The presented results confirm the advisability of using photocatalysis as a process preceding biodegradation. [ABSTRACT FROM AUTHOR]

The mechanism of sulfisoxazole (SFF) selective removal by photocatalysis in the presence of titanium (IV) oxide (TiO2) and iron (III) chloride (FeCl3) was explained and the kinetics and degradation pathways of SFF and other antibiotics were compared. The effects of selected inorganic ions, oxygen conditions, pH, sorption processes and formation of coordination compounds on the photocatalytic process in the presence of TiO2 were also determined. The Fe3+ compounds added to the irradiated sulfonamide (SN) solution underwent surface sorption on TiO2 particles and act as acceptors of excited electrons. Most likely, the SFF degradation is also intensified by organic radicals or cation organic radicals. These radicals can be initially generated by reaction with electron holes, hydroxyl radicals and as a result of electron transfer mediated by iron ions and then participate in propagation processes. The high sensitivity of SFF to decomposition caused by organic radicals is associated with the steric effect and the high bond polarity of the amide substituent. [ABSTRACT FROM AUTHOR]