Carbon nanotube as a nanoreactor for efficient degradation of 3-aminophenol over CoOx/CNT catalyst

Nanoreactors have been enlightened by enzymes to benefit from particular confinement for purpose of the acceleration of catalytic reactions and rendering them specific. Herein, we have first designed and synthesized the high-efficiency carbon nanotube-stabilized cobalt oxides nanoparticles (CoOx/CNT), via immobilization of CoOx nanoparticles onto carbon nanotube (CNT), for 3-aminophenol (3-AP) degradation via peroxymonosulfate (PMS) activation. Among them, carbon nanotube is used as a nanoreactor for efficient degradation of 3-AP over CoOx/CNT nanocomposite. The detailed physical characterizations illustrate that CoOx/CNT presented a nanotube-shaped structure, and some CoOx nanoparticles were encapsulated into CNT, and the molar ration of Co and O in CoOx was calculated to be 1:1.006, where CoO1.006 might be the mixture of CoO and Co3O4. The comparison with other carriers (including MoS2, CeO2, ZnO and ZrO2), CoOx/CNT provides the highest 3-AP degradation efficiency, highlighting the key role of CNT, as a nanoreactor, in CoOx/CNT for activating PMS to degrade 3-AP. The super-high catalytic activity of CoOx/CNT nanocomposite in the 3-AP degradation is owing to the specific confinement (encapsulation of some CoOx by carbon nanotubes). It seems the electron transfer from CNT to Co atom surface, enriched its surface electron cloud density, which is favorable for PMS activation. Quenching experiments and electron paramagnetic resonance (EPR) result have verified that SO4•- and OH• are the primary reactive oxygen species in 3-AP degradation over CoOx/CNT/PMS system. This study provides a new research orientation for the synthesis of efficient and stable carbon nanotube-encapsulated Co-based nanocatalyst for wastewater treatment.