Reduced graphene oxide promoted by SnO2 for photodegradation of tetracycline in water

Abstract

Abstract Reduced graphene oxide, with a high specific surface area and conductivity, also exhibits photocatalytic activity, and its photocatalytic performance improves with the addition of semiconductors. In this study, SnO 2 /reduced graphene oxide (RGO) composite was applied for tetracycline removal from water under visible light irradiation. The photocatalytic performance of RGO was enhanced through SnO 2 deposition. RGO was synthesized using Hummer’s method and subsequently impregnated with SnCl 2 solution to deposit SnO 2 . The effect of SnO 2 loading was investigated, and the calcination temperature was set at 400 °C. FTIR, XRD, Raman spectroscopy, SEM, TEM, BET, PL, and DRS analyses characterized the SnO 2 /RGO photocatalyst. SEM and TEM confirmed RGO layered morphology. PL analysis revealed an electron-hole recombination peak at 394 nm. DRS results showed a reduction in the band gap of SnO 2 /RGO composite compared to pristine SnO 2 and RGO. The effects of photocatalyst dosage, initial tetracycline concentration, and pH were studied and optimized using Design-Expert software (version 11) to maximize degradation efficiency. Under optimized conditions, with a tetracycline concentration of 10 mg/L, catalyst dosage of 4 g/L, pH of 7, and 10 min exposure to a 125 W LED lamp, 92% degradation was achieved. Kinetic analysis followed a second-order rate model. The reusability and regenerability of the SnO 2 /RGO composite were evaluated over five cycles, yielding tetracycline removal efficiencies of 91%, 73.25%, 65.7%, 60.3%, and 57%, respectively. Tetracycline removal was further assessed in the presence of Na + , Cl − , Mg 2+ , and NO 3 − , as well as using tap water. Compared with previous studies, this system demonstrated comparable removal efficiency within a substantially shorter reaction time under visible light irradiation, underscoring its economic potential for water treatment applications.