Ultrahigh-flux 2D CoO@MoS2 composite membrane activated peroxymonosulfate through enhanced electron transfer for rapid degradation of refractory benzotriazole

Abstract

The application of heterogeneous advanced oxidation processes (AOPs) in the removal of refractory pollutants has been hindered by several drawbacks, such as difficult recovery of the powder catalyst, the low yields and inefficient utilization of reactive oxygen species (ROS). We developed a novel catalytic membrane named 2D CoO@MoS2 membrane, its catalytic active layer was a composite material formed by MoS2 nanosheets wrapped and intercalated between 2D CoO porous nanoplates, providing abundant active sites and oxygen vacancies (Ov). 2D CoO@MoS2 membrane was applied to activate peroxymonosulfate (PMS) for benzotriazole (BTA) degradation. DFT calculations and series characterizations demonstrated that electron transfer occurred at the contact interface between 2D CoO and MoS2 phase, while the 2D CoO@MoS2 composite could act as an effective electron donor for PMS. The redox cycles of Mo(IV)/Mo(VI) and Ov/O2− could synergistically enhance the regeneration of Co(II), thereby maintaining the cycle of catalytic active center, which facilitated the spontaneous dissociation of PMS to generate various ROS, including SO4− (30.2 μM), 1O2 (8.6 μM) and OH (5.8 μM). These ROS rapidly degraded 99.7% of BTA (20 mg/L) through the nanoconfined layer of hydrophilic membrane with an ultra-high flux of 2172 L m−2h−1 in a super-fast time (∼195 ms). Surprisingly, the degradation rate constant k exhibited 3 to 5 orders of magnitude higher compared to conventional heterogeneous AOPs. Furthermore, the catalytic stability, degradation pathways and biological toxicity of BTA degradation were also evaluated. This membrane-based AOPs technique provides a new approach to overcome the limitations of conventional heterogeneous catalysis.