Highly efficient peroxymonosulfate activation by cobalt nanoparticles encapsulated in alginate-derived carbon for methylene blue degradation

Abstract

Sodium alginate, a bio-friendly and abundant precursor of biochar (BC), was employed to prepare biochar@Co catalysts (BC@Co). A series of catalysts was synthesised at different temperatures via a one-step carbothermal method with the aim of activating peroxymonosulfate (PMS) to degrade methylene blue (MB). For the BC@Co-T (T = 500–900 °C) catalysts, the degradation process of MB by PMS was consistent with the first-order reaction kinetics model, with reaction rate constants of 0.0471–0.8041 min⁻¹. In particular, the composite prepared at 900 °C (BC@Co-9) delivered the best PMS activation performance. Using the BC@Co-9–PMS system, the effects of various factors, including the catalyst dosage, PMS concentration, and coexisting ions, on the MB degradation rate were investigated. Under the optimal conditions of 0.005 g L⁻¹ BC@Co-9 and 0.6 mmol L⁻¹ PMS, the degradation rate of MB reached 100% in 18 min. Quenching experiments and electron paramagnetic resonance (EPR) measurements showed that ¹O₂ and ˙O₂⁻ were predominantly responsible for the degradation of MB in the BC@Co-9–PMS system. This study explored the application of sodium alginate as a recycled material and provides a feasible strategy for designing and fabricating environmentally friendly and efficient catalysts for the activation of PMS to degrade organic dyestuffs.