Degradation of sulfamethoxazole using peroxymonosulfate activated by self-sacrificed synthesized CoAl-LDH@CoFe-PBA nanosheet: Reactive oxygen species generation routes at acidic and alkaline pH

Abstract

Novel cobalt aluminum layered double hydroxide@cobalt aluminum Prussian blue analogs (CoAl-LDH@CoFe-PBA) nanosheet was synthesized via a self-sacrificed method from CoAl-LDH. The morphology and physicochemical properties characterization showed that CoAl-LDH@CoFe-PBA nanosheets were hexagon shape with diameter of 100 nm. Peroxymonosulfate (PMS) activation via CoAl-LDH@CoFe-PBA towards sulfamethoxazole (SMX) degradation was systematically examined. The catalytic system showed a satisfactory SMX degradation efficiency (over 80%) with the initial pH range of 3.0–9.0. In particular, only ~8 min was required to achieve 98% of SMX (40 μM) degradation with 0.1 g/L CoAl-LDH@CoFe-PBA and 0.3 mM PMS. Besides, the underlying reaction mechanism and generation routes of various reactive oxygen species (ROS) with varied initial pH was explicated by the electron paramagnetic resonance (EPR) and quenching tests. The surface-bound •OH and 1O2 were responsible for SMX degradation at acidic pH, and 1O2 was mainly produced from O2•−. At alkaline pH, SO4•− and 1O2 co-contributed to the degradation, while 1O2 was generated from O2•− and SO4•−. Oxygen vacancy in the inner space of the catalyst was considered as key electron donors involved in O2•− production. In addition, nine major degradation intermediates of SMX were identified and the possible degradation pathways were further proposed accordingly.