The binding effect and photooxidation on oxytetracycline with algal extracellular polymeric substances and natural organic matter

Authors

Yu Wang, Xinye Gong, Deying Huang, Shuwen Yan, Jibiao Zhang

Surface water contains a large amount of dissolved organic matter (DOM). Interactions between DOM and micropollutants have a significant impact on micropollutant degradation. In this study, algal extracellular polymeric substances (EPS) and natural organic matter (NOM) were selected as two DOM sources and oxytetracycline (OTC) as a representative micropollutant. EPS was mainly composed of tryptophan and protein-like organics, while NOM was mainly composed of fulvic acid-like, humic acid-like, and hydrophobic acid components. In addition, OTC degradation significantly decreased when bound with EPS and the C=O and C–H bonds of CH₂ or CH₃ groups may be involved in binding EPS and OTC, respectively, while –COOH may be involved in the binding of NOM and OTC. Furthermore, triplet intermediates were found to play a major role in OTC photodegradation in both EPS and NOM, with the contribution calculated as 49.96% and 44.61%, respectively. Steady-state concentrations of ³EPS* in EPS and ³NOM* in NOM were 3.59 × 10⁻¹⁴ mol L⁻¹ and 5.54 × 10⁻¹⁵ mol L⁻¹, respectively. These results provide new insights into the degradation of antibiotic-containing wastewater in the natural environment or engineering applications.