Co-doped carbon nitride nanosheets supported on SMFs for peroxymonosulfate activation to degrade tetracycline

Abstract

For the treatment of antibiotics contained wastewater, developing a highly efficient catalyst is key to peroxymonosulfate (PMS) activation and antibiotics degradation. In this work, nitrogen-doped carbon nanosheets (NCS) coated sintered metal fibers (SMFs) catalyst was designed and developed, which could positively promote the contacting efficiency between PMS, TC and catalysts. In specific, by the dip-coating of SMFs in the cobalt-contained dicyandiamide formaldehyde resin and the following pyrolyzing coordinated polymer procedure, it was possible to create a Co-doped NCS catalyst supported on SMFs. NCS with abundant exposed surface active sites could result in a relatively higher catalytic activity. Microscopy studies confirmed the presence of stacked NCS with high Co active sites loading, which was anchored on the surface of SMFs. The developed Co NCS/SMFs catalyst exhibited a highly degradation efficiency of 96% in 240 min. Effects of operating parameters (including PMS concentration and solution pH) on the TC elimination efficicency were also investigated. Additionally, Co NCS/SMFs exhibited good PMS activation activity in the wide pH range of 2.0–9.0, and acceptable recyclability with over 86% TC removal efficiency after five cycles test. According to SEM, XRD and XPS results, highly exposed active metal sites, O defects, Co-Nx sites and reactivity of Co0 in Co NCS/SMFs played an important role in the enhancement of degradation efficiency. Finally, radical inhibition experiment and corresponding EPR test revealedthe presence of SO4∙−, ∙OH, O2∙− and 1O2 in the TC degradation system, in which singlet oxygen (1O2) was demonstrated to be the dominating reactive species for PMS activation and TC degradation. This work provided an efficient strategy for developing robust monolithic lamellar catalyst for the continuous PMS activated degradation of TC.