The role of selected anions in the photodegradation of vancomycin in the aquatic environment

The efficiency of micropollutant photodegradation in aquatic matrices depends on several factors, including the presence of anions. They can act as radical scavengers and therefore inhibit the removal rate of micropollutants. Understanding the mechanisms of these interactions is crucial for the further development of advanced treatment technologies of water. Taking this into account, the main objective of the present study was to evaluate the effect of selected anions, such as Cl^- 2_-, SO₄, NO₃, and HCO₃, on the photolytic and photocatalytic degradation of vancomycin (VAN) in an aqueous matrix. The experiments were carried out in a solar simulator (Solarbox) using TiO₂ and ZnO as photocatalysts and Milli-Q water as an aquatic matrix. Additional tests were performed in the presence 2_- of peroxymonosulfate (PMS) and sulfate ions (SO₄) to assess their influence on VAN degradation efficiency in the sulfate radical-based advanced oxidation process. The results demonstrated that vancomycin photodegradation efficiency was significantly influenced by the type of anions present in the solution. The scavenging effects of reactive oxygen species increase in the following order: HCO₃-> NO₃ > Cl^- 2_- >SO₄. Moreover, the presence of sulfate ions adversely affected the PMS-assisted photodegradation, with a marked decrease in efficiency in most cases, except for TiO₂-based photocatalysis, where comparable removal was still achieved.