Sea Urchin-like NiCo 2 O 4 Catalyst Activated Peroxymonosulfate for Degradation of Phenol: Performance and Mechanism.

How to efficiently activate peroxymonosulfate (PMS) in a complex water matrix to degrade organic pollutants still needs greater efforts, and cobalt-based bimetallic nanomaterials are desirable catalysts. In this paper, sea urchin-like NiCo 2 O 4 nanomaterials were successfully prepared and comprehensively characterized for their structural, morphological and chemical properties via techniques, such as X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), among others. The sea urchin-like NiCo 2 O 4 nanomaterials exhibited remarkable catalytic performance in activating PMS to degrade phenol. Within the NiCo 2 O 4 /PMS system, the removal rate of phenol (50 mg L -1 , 250 mL) reached 100% after 45 min, with a reaction rate constant k of 0.091 min -1 , which was 1.4-times higher than that of the monometallic compound Co 3 O 4 /PMS system. The outstanding catalytic activity of sea urchin-like NiCo 2 O 4 primarily arises from the synergistic effect between Ni and Co ions. Additionally, a comprehensive analysis of key parameters influencing the catalytic activity of the sea urchin-like NiCo 2 O 4 /PMS system, including reaction temperature, initial pH of solution, initial concentration, catalyst and PMS dosages and coexisting anions (HCO 3 - , Cl - , NO 3 - and humic acid), was conducted. Cycling experiments show that the material has good chemical stability. Electron paramagnetic resonance (EPR) and quenching experiments verified that both radical activation (SO 4 •- , • OH, O 2 •- ) and nonradical activation ( 1 O 2 ) are present in the NiCo 2 O 4 /PMS system. Finally, the possible degradation pathways in the NiCo 2 O 4 /PMS system were proposed based on gas chromatography-mass spectrometry (GC-MS). Favorably, sea urchin-like NiCo 2 O 4 -activated PMS is a promising technology for environmental treatment and the remediation of phenol-induced water pollution problems.