Enhanced formation of sulfate radicals by metal-doped BiFeO3 under visible light for improving photo-Fenton catalytic degradation of 2-chlorophenol

- HO or SO4- are important species in the photo-Fenton catalytic oxidation of 2-CP.
- The coupling of S2O82− with Fe2+ and Cu2+ led to the effective formation of SO4-.
- Cu or Ba-Cu-doped BFO MNPs completely degraded 2-CP in less than 30 min with SO4-.

Three metal doped BiFeO3 magnetic nanoparticles (BFO MNPs), namely Bi1−xBaxFeO3 (x = 0.03), BiFe1−yCuyO3 (y = 0.1) and Bi1−xBaxFe1−yCuyO3 (x = 0.03, y = 0.1), were successfully prepared by a novel and simple sol-gel method. Then, iron and iron-copper heterogeneous Fenton-like photocatalysts were applied to activate H2O2 to hydroxyl radicals (OH) and persulfate (S2O82−) to sulfate radical anions (SO4-) for enhanced degradation of 2-chlorophenol (2-CP) from aqueous solution. Both Fe3+/Fe2+ and Cu+/Cu2+ pairs in the BFO MNPs systems effectively decomposed H2O2 to OH and S2O82− to SO4-. After only 70 min of visible light irradiation, Cu-doped BFO (BiFe1−yCuyO3) and Ba-Cu co-doped BFO (Bi1−xBaxFe1−yCuyO3) almost completely degraded 2-CP with reductions in total organic carbon (TOC) of 68 and 73%, respectively, which were much higher than that achieved with BFO and Ba-doped BFO, due to the formation of OH in the Cu2+/Fe2+/H2O2/visible light couple. However, 2-CP was completely degraded with Cu-doped BFO and Ba-Cu co-doped BFO in less than 30 min, due to the effective formation of SO4- in the Cu2+/Fe2+/S2O82−/visible light couple. Cu2+ or Fe2+ ions in H2O2/visible light or S2O82−/visible light couples are important species in the improved degradation of 2-CP in the photo-Fenton catalytic reaction. However, the photo-Fenton catalytic degradation of 2-CP was greatly reduced in the absence of any species of Cu2+ or Fe2+ ions, H2O2, S2O82−, and visible light irradiation.

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