Photocatalytic degradation of levofloxacin using ZnO/hydroxyapatite nanocomposite: Optimization using response surface methodology

Abstract

In this study, zinc oxide-hydroxyapatite (ZnO-HAp) nanocomposite was prepared via hydrothermal method for the photodegradation of levofloxacin. The effect of different HAp loadings of the nanocomposite showed that 90 % ZnOHAp has the highest % degradation toward levofloxacin (88.65 %). Then, the 90 % ZnOHAp was characterized with scanning electron microscopy (SEM) and transmission electron microscopy (TEM) which a revealed rod shaped ZnO (70–150 nm) adsorbed on hydroxyapatite plates (500 nm). X-ray diffraction (XRD) and Infrared spectroscopy (FTIR-ATR) confirmed the successful synthesis of ZnOHAp. The 90 % ZnOHAp nanocomposite was used as a photocatalyst to degrade aqueous levofloxacin under UV irradiation. Optimization of the photodegradation was performed using the response surface methodology (Box Behnken model). Analysis of variance of the model showed good predictability and goodness of fit (R² = 99.05 %, adjusted R² = 97.33 %, predicted R² = 91.54 %). The optimum parameters generated were 1.32 g/L catalyst dose, 4 ppm levofloxacin, pH 7.7 and the predicted photodegradation response was 99.99 % using 90 % ZnOHAp. Subsequent experimental verification yielded an actual % degradation of 91.69 % under the obtained optimized conditions. Additionally, the 90 % ZnOHAp phtocatalyst exhibited good recyclability over four cycles.