A rotating magnetic field propelled photocatalytic Fe3O4/g-C3N4 microrobot for degrading phenol and methylene blue: kinetics, mechanisms, and effect of water matrices

Abstract

Graphitic carbon nitride (g-C₃N₄) has attracted widespread attention in the photocatalytic degradation of pollutants due to its unique thermal and physicochemical properties, whereas the low photocatalytic efficiency and difficulties in recycling limit its use. To improve the photodegradation of phenol and methylene blue in water, a new rotating magnetic field (RMF) propelled photocatalytic Fe₃O₄/g-C₃N₄ (FC) microrobot system has been created. The results demonstrated that the integration of RMF significantly enhanced the photocatalytic degradation of phenol and methylene blue by the Fe₃O₄/g-C₃N₄ microrobot. Under conditions of 1 g/L catalyst dosage and 2 A RMF excitation current, the Fe₃O₄/g-C₃N₄ microrobot with 20 % (w/w) Fe₃O₄ content (FC20) exhibited the highest photocatalytic activity, achieving 92.8 % degradation of phenol and >99.9 % degradation of methylene blue within 300 min. Furthermore, FC20 demonstrated excellent reusability, maintaining high degradation efficiency after four consecutive cycles. Factors such as magnetic induction, photocatalyst dosage, and pH were found to influence the degradation efficiency of phenol and methylene blue by Fe₃O₄/g-C₃N₄ microrobots. Additionally, the effects of inorganic ions and water matrices on the degradation of phenol and methylene blue were investigated. By studying the degradation mechanisms, it was revealed that the order of influence of reactive species during the photodegradation process was: h⁺>·O₂⁻>·OH. In conclusion, the combined FC-RMF system has great potential for improving the removal of phenol and methylene blue pollutants from water.