Surface-active bismuth ferrite as superior peroxymonosulfate activator for aqueous sulfamethoxazole removal:...

A surface-active Bi₂Fe₄O₉ nanoplates (BF-nP) was prepared using a facile hydrothermal protocol for sulfamethoxazole (SMX) removal via peroxymonosulfate (PMS). The catalytic activity of BF-nP was superior to other catalysts with the following order of performance: BF-nP>Bi₂Fe₄O₉ (nanocubes)>>Co₃O₄>Fe₂O₃ (low temperature co-precipitation method)>Fe₂O₃ (hydrothermal method)∼Bi₂O₃∼Bi³⁺∼Fe³⁺. The empirical relationship of the apparent rate constant (k_app), BF-nP loading and PMS dosage can be described as follows: k_app=0.69[BF-nP]^0.6[PMS]^0.4 (R²=0.98). The GC-MS study suggests that the SMX degradation proceed mainly through electron transfer reaction. The XPS study reveals that the interconversion of Fe³⁺/Fe²⁺ and Bi³⁺/Bi⁵⁺ couples are responsible for the enhanced PMS activation. The radical scavenging study indicates that SO₄^- is the dominant reactive radical (>92% of the total SMX degradation). A method to quantify SO₄^- in the heterogeneous Bi₂Fe₄O₉/PMS systems based on the quantitation of benzoquinone, which is the degradation byproduct of p-hydroxybenzoic acid and SO₄^-, is proposed. It was found that at least 7.8±0.1μM of SO₄^- was generated from PMS during the BF-nP/PMS process (0.1gL^-1, 0.40mM PMS, natural pH). The Bi₂Fe₄O₉ nanoplates has a remarkable potential for use as a reusable, nontoxic, highly-efficient and stable PMS activator.