Co3O4 nanocube-decorated nitrogen-doped carbon foam as an enhanced 3-dimensional hierarchical catalyst for activating Oxone to degrade sulfosalicylic acid

Abstract

As sulfosalicylic acid (SUA) is extensively used as a pharmaceutical product, discharge of SUA into the environment becomes an emerging environmental issue because of its low bio-degradability. Thus, SO₄^--based advanced oxidation processes have been proposed for degrading SUA because of many advantages of SO₄^-. As Oxone represents a dominant reagent for producing SO₄^-, and Co is the most capable metal for activating Oxone to generate SO₄^-, it is critical to develop an effective but easy-to-use Co-based catalysts for Oxone activation to degrade SUA. Herein, a 3D hierarchical catalyst is specially created by decorating Co₃O₄ nanocubes (NCs) on macroscale nitrogen-doped carbon form (NCF). This Co₃O₄-decorated NCF (CONCF) is free-standing, macroscale and even squeezable to exhibit interesting and versatile features. More importantly, CONCF consists of Co₃O₄ NCs evenly distributed on NCF without aggregation. The NCF not only serves as a support for Co₃O₄ NCs but also offers additional active sites to synergistically enhance catalytic activities towards Oxone activation. Therefore, CONCF exhibits a higher catalytic activity than the conventional Co₃O₄ nanoparticles for activating Oxone to fully eliminate SUA in 30 min with a rate constant of 0.142 min^-1. CONCF exhibits a much lower Ea value of SUA degradation (35.2 kJ/mol) than reported values, and stable catalytic activities over multi-cyclic degradation of SUA. The mechanism of SUA degradation is also explored, and degradation intermediates of SUA degradation are identified to provide a possible pathway of SUA degradation. These features validate that CONCF is certainly a promising 3D hierarchical catalyst for enhanced Oxone activation to degrade SUA. The findings obtained here are also insightful to develop efficient heterogeneous Oxone-activating catalysts for eliminating emerging contaminants.

Keywords: Carbon foam; Co(3)O(4); Cobalt oxide; Nitrogen; Oxone; Sulfosalicylic acid.