Photo-assisted removal of doxycycline using H2O2 and simulated sunlight: Operational parameters optimization and ecotoxicity assessment

Abstract

The presence of antibiotics in different environmental matrices is a problem of great concern. Doxycycline (DOX) is an antibiotic belonging to the family of tetracyclines, whose use has been extensive in the treatment of different diseases. DOX residues have been found in different water bodies, which implies that conventional water treatment technologies are not enough to remove these types of pollutants. This study sought to evaluate the application of simulated sunlight and H2O2 in the removal of DOX at laboratory scale. Effects of different operational parameters including the solution initial pH and the peroxide concentration were studied. The results indicated that DOX elimination was higher at alkaline conditions and that increasing the H2O2 concentration has a positive effect. Pollutant total elimination was achieved in 40 min of reaction under optimized conditions. Additionally, the assessment of the effect of the initial DOX concentration allowed to establish that a pseudo-first order kinetic model fits the experimental data adequately. Data related to the dissolved organic carbon (DOC) and nitrates present in the treated samples were also analyzed. Finally, in terms of the solution ecotoxicity, variation on the bioluminescence of Vibrio fischeri bacteria, showed that evaluated photo-treatment is efficient not only to reduce the DOX presence but also, to inhibit samples toxicity.