Synthesis and Characterization of MXene/g-C3N4 Hybrid Nanocomposite for Photocatalytic Degradation of Ciprofloxacin Antibiotic

Background and Objective: The contamination of water resources with antibiotics has emerged as a significant global challenge due to its detrimental effects on both the environment and human health. Photocatalytic processes have been recognized as an effective strategy for removing these hazardous contaminants. In this study, a novel nanocomposite based on graphitic carbon nitride (g-C3N4) and MXene (Ti3C2) nanosheets was synthesized and evaluated for the photocatalytic degradation of the antibiotic ciprofloxacin.
Materials and Methods: Graphitic carbon nitride (g-C3N4) was synthesized through the thermal polymerization of melamine at 550°C in a tube furnace. MXene (Ti3C2) nanosheets were prepared by chemically etching the AlC2 MAX phase with a solution of HCl/LiF for 48 hours.
MXene/g-C3N4 nanocomposites were synthesized using a simple self-assembly method that relies on the electrostatic attraction between the graphitic carbon nitride nanosheets and varying weight percentages of MXene nanosheets (0.1%, 0.3%, 0.5%, 0.7%, and 0.9% by weight). The synthesized nanomaterials were characterized using XRD, BET, DRS, and PL analyses.
Results and Discussion: X-ray diffraction (XRD) analysis of the MXene/g-C3N4 nanocomposite revealed characteristic peaks at 13° and 27°, corresponding to graphitic carbon nitride, as well as peaks at 9° and 62°, attributable to MXene ((Ti3C2) nanosheets. These findings indicate the preservation of the primary structures of both nanomaterials within the composite and confirm the successful synthesis of the nanocomposite. Brunauer-Emmett-Teller (BET) analysis demonstrated that bulk Graphitic carbon nitride exhibited the lowest surface area of 6.3 m²/g among the samples, which resulted in negligible photocatalytic performance. Following protonation with hydrochloric acid and ultrasonic treatment, the surface area of the bulk sample increased to 25.6 m²/g for graphitic carbon nitride nanosheets. Furthermore, the specific surface areas of MXene nanosheets and the MXene/g-C3N4 nanocomposite with a 7 wt% MXene loading (CN/MX7) were measured at 20.2 m²/g and
18.3 m²/g, respectively. Diffuse reflectance spectroscopy (DRS) analysis indicated that the bandgap energy of the photocatalysts decreased from 2.72 eV for the bulk sample to 2.47 eV for the CN/MX7 nanocomposite, which enhances charge carrier separation and improves photocatalytic activity. The reduced intensity of the photoluminescence (PL) spectra of the synthesized photocatalysts confirmed a lower rate of electron-hole recombination. Results from ciprofloxacin antibiotic removal experiments demonstrated that the photocatalyst synthesized with a 7 wt% MXene loading (CN/MX7) achieved the highest removal percentage of 94.02% at a ciprofloxacin concentration of 10 mg/L, a photocatalyst dosage of 1 g/L, a pH of 5, and under 50 W LED visible light irradiation for 120 minutes. Kinetic studies revealed that the photocatalytic degradation of ciprofloxacin by the CN/MX7 photocatalyst followed a pseudo-first-order kinetic model. Additionally, recyclability and stability tests indicated that the CN/MX7 photocatalyst retained 96% of its photocatalytic degradation capability after five cycles of antibiotic removal and photocatalyst regeneration.
Conclusion: This research demonstrated that the CN/MX7 nanocomposite, due to the unique properties of graphitic carbon nitride and MXene (Ti3C2) nanosheets, serves as a highly efficient photocatalyst. The nanocomposite effectively removed the antibiotic ciprofloxacin from aqueous solutions, thereby presenting itself as a viable option for purifying water contaminated with pharmaceutical substances.