Vacancy-Rich CoS x @LDH@Co-NC Catalytic Membrane for Antibiotic Degradation with Mechanistic Insights

Improving the wettability of carbon-based catalysts and overcoming the rate-limiting step of the Mn+1/Mn+ cycle are effective strategies for activating peroxymonosulfate (PMS). In this study, the coupling of Co-NC, layered double hydroxide (LDH), and CoSx heterostructure (CoSx@LDH@Co-NC) was constructed to completely degrade ofloxacin (OFX) within 10 min via PMS activation. The reaction rate of 1.07 min(-1) is about 1-2 orders of magnitude higher than other catalysts. The interfacial effect of confined Co-NC and layered double hydroxide (LDH) not only enhanced the wettability of catalysts but also increased the vacancy concentration; it facilitated easier contact with the interface reactive oxygen species (ROS). Simultaneously, reduced sulfur species (CoSx) accelerated the Co3+/Co2+ cycle, acquiring long-term catalytic activity. The catalytic mechanism revealed that the synergistic effect of hydroxyl groups and reduced sulfur species promoted the formation of O-1(2), with a longer lifespan and a longer migration distance, and resisted the influence of nontarget background substances. Moreover, considering the convenience of practical application, the CoSx@LDH@Co-NC-based catalytic membrane was prepared, which had zero discharge of OFX and no decay in continuous operation for 5.0 h. The activity of the catalytic membrane was also verified in actual wastewater. Consequently, this work not only provides a novel strategy for designing excellent catalysts but also is applicable to practical organic wastewater treatment.

Automated summary

In this study, a CoSx@LDH@Co-NC heterostructure was constructed for activating peroxymonosulfate (PMS) and degrading ofloxacin (OFX) efficiently. The catalyst exhibited a high reaction rate and long-term catalytic activity due to the enhanced wettability and vacancy concentration by the confined Co-NC and layered double hydroxide (LDH), as well as the accelerated Co3+/Co2+ cycle by the reduced sulfur species (CoSx).