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

A surface-active BiFeO 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>BiFeO (nanocubes)>>CoO>FeO (low temperature co-precipitation method)>FeO (hydrothermal method)∼BiO∼Bi∼Fe. The empirical relationship of the apparent rate constant (k), BF-nP loading and PMS dosage can be described as follows: k=0.69[BF-nP][PMS] (R=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 Fe/Fe and Bi/Bi couples are responsible for the enhanced PMS activation. The radical scavenging study indicates that SO is the dominant reactive radical (>92% of the total SMX degradation). A method to quantify SO in the heterogeneous BiFeO/PMS systems based on the quantitation of benzoquinone, which is the degradation byproduct of p-hydroxybenzoic acid and SO, is proposed. It was found that at least 7.8±0.1μM of SO was generated from PMS during the BF-nP/PMS process (0.1gL, 0.40mM PMS, natural pH). The BiFeO nanoplates has a remarkable potential for use as a reusable, nontoxic, highly-efficient and stable PMS activator.