Fabrication of chitosan-MnO2‑iridium/nanoceria supported nanoparticles: Catalytic and anti-radical activities

Chitosan capped MnO2‑iridium nanoparticles supported on nanoceria (Ch-MnO2-Ir/CeO2) were fabricated by using combination of colloidal solution and metal displacement galvanic methods. The oxidative degradation of acid orange 7 in aqueous solution by activated persulfate with the as-prepared nanoparticles was studied. The resulting Ch-MnO2-Ir/CeO2 with S2O82-, 80 % degraded 70.06 mg/L of acid orange 7 within 100 min, while at the same time, Ch-Ir, Ch-MnO2, and Ch-Ir-MnO2 remained inactive. CeO2 increased the surface of the catalyst, and also improved the reactive oxygen species site of Ch-Ir-MnO2 through the activation of S2O82- with CeO2. The reversible redox cycle reaction, Ce (III) ↔ Ce (IV) and strong synergistic effect of MnO2-Ir are responsible for the remarkable catalytic performance of Ch-MnO2-Ir/CeO2/S2O82- system. The degradation of acid orange 7 could be significantly retarded with inorganic (NO3- < Cl- < SO42- < H2PO4- < HCO3-) and organic scavengers (ethanol < tertiary butanol < benzoquinone < phenol). Ch-MnO2-Ir/CeO2 exhibited excellent stability and reusability. Anti-radical activity of chitosan and Ch-MnO2-Ir/CeO2 was evaluated with 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical. The free radical properties increase with concentration of chitosan and Ch-MnO2-Ir/CeO2.