Emerging NiO–rGO Nanohybrids for Antibiotic Pollutant Degradation under Visible-Light Irradiation

The continuous increase in the discharge of unregulated chemical waste from various industries has prompted the need to remove organic pollutants. Photocatalysts have garnered tremendous attention owing to their advantages of eliminating pollutants without harmful products, low cost, and easy control. In this study, NiO nanocubes and NiO–reduced graphene oxide (rGO) nanohybrids were fabricated using a simple hydrothermal method. The chemical bonding and structural, morphological, absorption, and photocatalytic properties of the prepared NiO–rGO nanohybrids were characterized. The results showed that graphene could be successfully hybridized with the NiO nanocubes. The surface area supported the better light absorption perfromnace of the NiO–rGO nanohybrids. Hence, the separation rate of electron-hole pairs has been accelerated. The NiO-rGO nanohybrids significantly improved the degradation efficiency of the antibiotics, such as ciprofloxacin (Cipxn) and tetracycline (TetC), compared to pure NiO. NiO–rGO with 20 mg rGO exhibited the highest degradation efficiency for Cipxn (91.5%) and TetC (94.75%) under visible light irradiation. Further, the impact of several variables, such as the catalyst dose and starting solution concentration, on the pollutant degradation and related first-order kinetic constants were assessed. The trapping test results showed that the •OH and •O2 radicals are involved in the photocatalytic activity. Moreover, the catalysts exhibited good reusability and stability over four cycles. Therefore, the NiO–rGO nanohybrids can be potential photocatalysts for converting energy and cleaning the environment.