Evaluation of water matrix effects, experimental parameters, and the degradation pathway during the TiO₂ photocatalytical treatment of the antibiotic dicloxacillin

Abstract

The photocalytic degradation of dicloxacillin (DXC) using TiO₂ was studied in synthetic and natural waters. The degradation route and the effect of different experimental variables such as pH, applied power, and the initial concentrations of DXC and the catalyst were investigated. The best performances were achieved at a natural pH 5.8 and using 2.0 g L⁻¹ of TiO₂ with 150 W of applied power. The photodegradation process followed Langmuir-Hinshelwood kinetics. The water matrix effect was evaluated in terms of degradation efficiency in the presence of organic compounds (oxalic acid, glucose), Fe²⁺ ion and natural water. An increase in degradation was observed when ferrous ion was part of the solution, but the process was inhibited with all evaluated organic compounds. Similarly, inhibition was observed when natural water was used instead of distilled water. The extent of degradation of the process was evaluated following the evolution of chemical oxygen demand (COD), antimicrobial activity (AA), total organic carbon (TOC) and biochemical oxygen demand (BOD₅). Total removal of DXC was achieved after 120 min of treatment and 95% mineralization was observed after 480 min of treatment. Additionally, the total removal of antimicrobial activity and a high level of biodegradability were observed after the photocalytical system had been operating for 240 min.

Keywords:

• Advanced oxidation process
• antibiotics
• dicloxacillin
• mineralization
• photocatalysis with TiO₂
• water matrix
• water treatment

Funding

The authors would like to thank the Administrative Department of Science, Technology and Innovation (Colciencias, Colombia) for its financial support through the project: “Implementación de metodologías eficientes y confiables para degradar residuos de antimicrobianos en el hogar y en efluentes industrials.”