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

## TL;DR

This study shows that a composite of reduced graphene oxide and SnO2 can efficiently break down tetracycline in water under visible light, with high degradation rates and potential for reuse.

## Contribution

The novel contribution is the development of a SnO2/reduced graphene oxide composite that achieves rapid and efficient tetracycline degradation under visible light.

## Key findings

- The SnO2/RGO composite achieved 92% tetracycline degradation under optimized conditions in just 10 minutes.
- The composite showed good reusability, maintaining over 90% efficiency in the first cycle and remaining effective for five cycles.
- The system outperformed previous methods in terms of reaction time while maintaining comparable removal efficiency.

## 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, SnO2/reduced graphene oxide (RGO) composite was applied for tetracycline removal from water under visible light irradiation. The photocatalytic performance of RGO was enhanced through SnO2 deposition. RGO was synthesized using Hummer’s method and subsequently impregnated with SnCl2 solution to deposit SnO2. The effect of SnO2 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 SnO2/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 SnO2/RGO composite compared to pristine SnO2 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 SnO2/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−, Mg2+, and NO3−, 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.

The online version contains supplementary material available at 10.1038/s41598-025-32230-4.