Carbon-nitride-based micromotor driven by chromate-hydrogen peroxide redox system: Application for removal of...

In this study, a Janus Fe/C₃N₄ micromotor driven by a chromate-hydrogen peroxide (Cr(VI)/H₂O₂) redox system was developed and its movement was analyzed. The motion of the micromotor was tracked via nanoparticle tracking analysis (NTA) and the corresponding diffusion coefficients (D) were determined. The NTA results revealed that D = 0 in water in the absence of additives (Cr(VI) or H₂O₂). The addition of H₂O₂ resulted in an increase in D from 0 to 12 × 10⁶ nm² s^-1, which further increased to 20 × 10⁶, 26.5 × 10⁶, 29 × 10⁶, and 44 × 10⁶ nm² s^-1 with the addition of 0.5, 1, 2, and 5 ppm of Cr(VI), respectively. Cr(VI) alone did not efficiently propel the Fe/C₃N₄-based micromotor. Therefore, it was proposed that the Cr(VI)/H₂O₂ redox system generates O₂, which plays a major role in the movement of the C₃N₄-based micromotor. In addition, the formation of reactive species, such as OH and ¹O₂, was confirmed through electron spin resonance experiments. The reactive species efficiently degraded sulfamethaxazole (SMX), an organic pollutant, as demonstrated through degradation studies and product analyses. The effects of various parameters, such as H₂O₂ concentration, Cr(VI) concentration, and initial pH on the movement of micromotor and degradation of SMX were also documented.