Enhanced degradation of 5-sulfosalicylic acid using peroxymonosulfate activated by ordered porous silica-confined Co₃O₄ prepared via a solvent-free confined space strategy

As 5-sulfosalicylic acid (SSA) is extensively consumed as a medical intermediate, SSA is continuously released into the environment. Due to its poor bio-degradability, SSA in water has posed threats to aquatic organisms. Therefore, advanced oxidation processes (AOPs) should be adopted for eliminating SSA. In view of many advantages of SO₄^[rad]−-based AOPs, it is necessary to develop SO₄^[rad]−-based AOPs for treating SSA. As peroxymonosulfate (PMS) is selected as a source of SO₄^[rad]−, a Co-based heterogeneous catalyst is fabricated by a confined space strategy (CSS) to load Co₃O₄ into pores of ordered porous silica (OPS). Unlike the conventionally-prepared Co-loaded OPS, which loads Co onto the template-free OPS (FS) to form CoFS, the proposed OPS-confined Co₃O₄ was fabricated through grinding Co into the template-retained OPS (TS), which consists of silanol groups. The OH groups of these silanol groups attract Co precursors and facilitate insertion of Co into pores of TS, resulting in CoTS. These morphologic differences between CoTS and CoFS leads to significantly different catalytic activities for PMS activation to degrade SSA. When CoFS is incapable of activating PMS effectively to degrade SSA, CoTS-activated PMS completely degrades SSA within 60 min. CoTS also exhibits much higher catalytic activities than commercial Co₃O₄ NPs for activating PMS to degrade SSA. In addition, CoTS-activated PMS shows a lower E_a than other catalysts for activating PMS to degrade pollutants. Degradation pathway of SSA is also proposed based on degradation intermediates. These results and findings validate that CoTS can be a promising and advantageous heterogeneous catalyst, which could be conveniently prepared, for activating PMS to degrade the emerging contaminant, SSA.