Cobalt ferrite nanoparticle-loaded nitrogen-doped carbon sponge as a magnetic 3D heterogeneous catalyst for monopersulfate-based oxidation of salicylic acid.

As salicylic acid (SAL) is increasingly consumed as a pharmaceutical product, release of SAL into the environment poses threats to ecology because of its low bio-degradability. Thus, SO4•--based chemical oxidation processes have been proposed for degrading SAL. Since monopersulfate (MPS) represents a primary reagent for generating SO4•-, and Co is the most capable metal for activating MPS to generate SO4•-, C3O4 NPs are frequently proposed for activating MPS but they are difficult to recover from water. Thus CoFe2O4 is considered as a magnetic alternative to Co3O4, and loading of CoFe2O4 NPs on substrates could further improve dispersion and avoid aggregation of NPs. Therefore, this study proposes a 3-Dimensional (3D) hierarchical catalyst which is fabricated by loading CoFe2O4 NPs on nitrogen-doped carbon sponge (NCS). The NCS is not only adopted as a support for CoFe2O4 NPs but also provides additional catalytic sites and enhances catalytic activities of CoFe2O4 NPs for MPS activation. As a result, CoFe2O4 NPs loaded on NCS (CFNCS) exhibits substantially higher catalytic activities than CoFe2O4 NPs and NCS individually with 100% of SAL could be afforded within 30 min. Ea of SAL degradation of 47.4 kJ/mol by CFNCS-activated MPS is also lower than those by other reported catalysts, whereas the RSE was 11.1%, which was also much higher than most of reported values. These features demonstrate that CFNCS is a promising 3D catalyst for enhancing MPS activation to degrade SAL. The findings obtained here are also insightful to develop efficient MPS-activating catalysts for eliminating contaminants.