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

FeO magnetic nanoparticles (MNPs) are attractive heterogeneous Fenton-like catalysts for oxidative degradation of organic pollutants with HO. Herein highly efficient and stable FeO MNPs (FeO-op-DES, ca. 10nm) were successfully prepared via a novel oxidative precipitation-combined ionothermal synthesis, which comprised oxidative precipitation of FeSO·7HO in choline chloride:2urea deep eutectic solvent. Among five different FeO particles tested, FeO-op-DES MNPs exhibited the highest catalytic activity with the activation energy of 47.6kJmol for degradation of Rhodamine B (RhB) with HO under the same conditions (FeO dosage of 0.50gL, HO concentration of 40mmolL, pH 6.4, 55°C, 2h). FeO-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 after having been continuously running for 12h). The superior catalytic performance of FeO-op-DES MNPs was attributed to the combination of multiple technologically important features, including the nanometer size, high Fe 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 FeO-op-DES MNPs was also demonstrated by the degradation of four other organic pollutants.