Heterogeneous activation of peroxymonosulfate by Co-doped Fe 2 O 3 nanospheres for degradation of p-hydroxybenzoic acid.

Environmental remediation has become more effective when using nanotechnologies. In this study, iron oxide (α-Fe2 O3 ) nanospheres with different cobalt doping levels (xCo-Fe2 O3 ) were synthesised and applied in the heterogeneous activation of peroxymonosulfate (PMS) for the degradation of p-hydroxybenzoic acid (p-HBA). The catalyst (3Co-Fe2 O3 ) with 3% Co doping exhibits the best performance for PMS activation, possibly because of the larger specific surface area and the tailored catalyst surface as confirmed by X-ray photoelectron spectroscopy (XPS). Reaction parameters were investigated to optimise the degradation efficiency. The metal ions leaching tests confirmed the higher stability of the catalyst, thanks to the leaching suppression by the doping of Co2+ . The main contribution of free radicals (SO4 •- and • OH) was confirmed by electron paramagnetic resonance (EPR) spectra, whereas partial contribution of oxygen anions and singlet oxygen (O2 •- , 1 O2 ) was observed during the quenching tests. Finally, a radical based degradation mechanism was proposed for the removal of p-HBA. It is expected to open up a novel perspective for the application of iron oxide as a potential catalyst for the removal of emerging contaminants.