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

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.