Hierarchically porous structure of two-dimensional nano-flakes assembled flower-like NiO promotes the formation of surface-activated complex during persulfate activation

Heterogeneous catalysts with hierarchically porous structure are highly efficient to catalyze chemical reactions. In this work, two-dimensional (2D) nano-flakes assembled flower-like NiO is fabricated and utilized for activating peroxydisulfate (PDS) to degrade organic pollutants bisphenol A (BPA). The results demonstrate that the prepared catalyst exhibits well organized flower structure composed of uniform 2D nano-flakes. PDS combines with the catalyst to form surface-activated NiO-PDS complex, subsequently depriving electrons from BPA. For the optimized NiO-12 catalyst, large specific surface area and hierarchically porous structure benefit to exposes abundant active sites while low resistance promotes electrons transfer, bringing the high BPA degradation rate constant of 0.28 min⁻¹ under the condition of 20 mg/L initial concentration. NiO-12 exerts a capability of catalyzing PDS to mineralize 34% of practical packaging wastewater. This study provides a new strategy to fabricate hierarchical 2D porous catalysts for persulfate activation, with application potential in practical wastewater treatment.