REMOVAL OF VETERINARY ANTIBIOTICS BY USING LAYERED DOUBLE HYDROXIDE PHOTOCATALYSTS: EFFECTS OF REACTION PARAMETERS AND KINETIC MODELLING

The photocatalytic performances of Ni-Fe-LDH, Co-Fe-LDH, and Cu-Fe-LDH, (LDH: Layered Double Hydroxide) were investigated for the removal of oxytetracycline hydrochloride (OTC-HCl) from water. Layered double hydroxide materials were synthesized by using the co-precipitation method. The photocatalysts were characterized by SEM, XRD, XPS, and BET surface area analyses. The highest pharmaceutical removal efficiency was obtained by using Ni-Fe-LDH photocatalyst. Box-Behnken design was used to examine the influences of reaction parameters on OTC-HCl removal and to determine the optimal reaction conditions. In the parametric study, the interactive influences of photocatalyst loading, solution pH, and the initial oxidant concentration on oxytetracycline hydrochloride removal were investigated. Under visible light irradiation, the optimal conditions were determined to be 1.5 g/L catalyst loading, pH 5, and 1.48 mM H2O2 concentration by using Ni-Fe-LDH photocatalyst. OTC-HCl degradation was calculated as 67.1% under the optimal conditions. Hydroxyl radical was determined to be the main effective reactive. Phytotoxicity tests were performed using Lepidium sativum seeds. Veterinary antibiotic degradation fit to first order reaction. The Arrhenius constant and activation energy were evaluated as 2.6 min-1 and 14.21 kJ/mol, respectively.