Ionothermal synthesis of Fe3O4 magnetic nanoparticles as efficient heterogeneous Fenton-like catalysts for degradation of organic pollutants with H2O2.

Fe3O4 magnetic nanoparticles (MNPs) are attractive heterogeneous Fenton-like catalysts for oxidative degradation of organic pollutants with H2O2. Herein highly efficient and stable Fe3O4 MNPs (Fe3O4-op-DES, ca. 10nm) were successfully prepared via a novel oxidative precipitation-combined ionothermal synthesis, which comprised oxidative precipitation of FeSO4·7H2O in choline chloride:2urea deep eutectic solvent. Among five different Fe3O4 particles tested, Fe3O4-op-DES MNPs exhibited the highest catalytic activity with the activation energy of 47.6kJmol-1 for degradation of Rhodamine B (RhB) with H2O2 under the same conditions (Fe3O4 dosage of 0.50gL-1, H2O2 concentration of 40mmolL-1, pH 6.4, 55°C, 2h). Fe3O4-op-DES MNPs were magnetically recoverable, and had good catalytic stability and recyclability without the need of regeneration (>98% degradation efficiency of RhB in 2h and pseudo-first-order rate constant of 0.0376min-1 after having been continuously running for 12h). The superior catalytic performance of Fe3O4-op-DES MNPs was attributed to the combination of multiple technologically important features, including the nanometer size, high Fe2+ content, large surface area, high density of surface active sites and stable crystal structure (no phase transformation, negligible iron leaching and particle aggregation after reaction). The wide applicability of Fe3O4-op-DES MNPs was also demonstrated by the degradation of four other organic pollutants.