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

Abstract

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. E_a 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.

Keywords: Carbon sponge; Cobalt ferrite; Monopersulfate; Nitrogen; Salicylic acid.