Hollow porous cobalt oxide nanobox as an enhanced for activating monopersulfate to degrade 2-hydroxybenzoic acid in water

As 2-hydroxybenzoic acid (HBA) represents a typical pharmaceutical and personal care product (PPCP), constant releasing of HBA into the environment poses threats to the ecology, and thus it is critical to develop effective techniques to remove HBA from water. Recently, sulfate radical (SO4‒)-based advanced oxidation processes involved with monopersulfate (MPS) activation are proven as effective approaches for eliminating PPCPs from water, and Co3O4 is recognized as a capable catalyst for activating MPS. Therefore, great interests have arisen to develop Co3O4-based catalysts with advantageous morphologies and characteristics for enhancing catalytic activities. Therefore, a special Co3O4-based material is proposed in this work. Through a surfactant-assisted strategy, a cubic Co-MOF is prepared and used as a precursor, which is etched to afford hollow structure, and then transformed into hollow porous Co3O4 nanobox (PCNB). PCNB can exhibit distinct reactive surface with abundant surface oxygen vacancy as well as physical properties in comparison to the commercial Co3O4 NPs (com-Co3O4 NP), thereby leading to the outstanding catalytic activity of PCNB for activating MPS to degrade HBA. The activation energy (Ea) of 46.2 kJ/mol is also calculated using PCNB + MPS system, which is much lower than most of recent reported studies for activating MPS. PCNB could be also reusable over 5 consecutive HBA degradation cycles. The activation mechanism of MPS by PCNB and HBA degradation pathway are also comprehensively elucidated via experimental evidences and the theoretical calculation to offer insightful information of development of Co3O4 for HBA degradation.