Surface-active bismuth ferrite as superior peroxymonosulfate activator for aqueous sulfamethoxazole removal: Performance, mechanism and quantification of sulfate radical.

A surface-active Bi2 Fe4 O9 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>Bi2 Fe4 O9 (nanocubes)>Co3 O4 >Fe2 O3 (low temperature co-precipitation method)>Fe2 O3 (hydrothermal method)∼Bi2 O3 ∼Bi3+ ∼Fe3+ . The empirical relationship of the apparent rate constant (kapp ), BF-nP loading and PMS dosage can be described as follows: kapp =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 Bi2 Fe4 O9 /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 Bi2 Fe4 O9 nanoplates has a remarkable potential for use as a reusable, nontoxic, highly-efficient and stable PMS activator.