Ultrasound assisted Fenton-like degradation of dyes using copper doped graphitic carbon nitride

A novel copper doped graphitic carbon nitride (Cu-C₃N₄) was successfully synthesized and used as an effective Fenton-like catalyst. Cu-C₃N₄ was characterized by scanning electron microscopy, surface area analyzer, Fourier transform infrared spectroscopy, X-ray diffractometer, and X-ray photoelectron spectroscopy. Effect of process parameters including catalyst dosage, hydrogen peroxide (H₂O₂) concentration, solution pH, and initial methylene blue (MB) concentration was investigated to evaluate catalytic performance. The pseudo first-order kinetic model was used to describe the catalytic process. The enhancement of MB degradation is observed assisted by ultrasound. MB degradation of 96% is obtained within 30 min in Cu-C₃N₄/H₂O₂/ultrasound system, and the corresponding rate constant is 0.099 min^-1. Effective MB degradation is obtained over a broad pH range (3.3-9.9). The catalytic mechanism is examined by ultraviolet-visible spectra, quenching test, and electron spin resonance determination. The dominant mechanism of MB degradation is ascribed to the ultrasonic H₂O₂ activation by Cu-C₃N₄ for hydroxyl radical generation. Cu-C₃N₄ has good reusability and is effective to degrade rhodamine B and acid orange 7. This work not only contributes to the field of wastewater treatment, but also provides insights into the synthesis of Fenton-like catalysts. The results manifest that Cu-C₃N₄ is a promising Fenton-like catalyst for dye degradation in the field of environmental pollution remediation.