N-doped graphene aerogels as efficient heterogeneous catalytic activators for peroxymonosulfate to remove 2-sec-butyl-4,6-dinitrphenol (DNBP) in aqueous solution

Abstract The nitrogen-doped graphene aerogels (NGAs) with interconnected hierarchical porous structures were facilely prepared via hydrothermal process in the mixed aqueous solution of ethylenediamine (EDA) and urea and post-freeze-drying treatment. A series of NGAs samples with different GO:urea:EDA mass ratios were obtained and characterized by Raman, FT-IR, XPS, TEM and SEM. The prepared NGAs were employed as metal-free carbocatalysts in the activation of peroxymonosulfate (PMS) for 2-sec-butyl-4,6-dinitrphenol (DNBP) degradation in aqueous solution. The resultant NGA-4 catalyst with GO:urea:EDA mass ratio of 3:2:4 exhibited the best catalytic activity in PMS activation for oxidative degradation of DNBP among the prepared NGAs samples. The effects of temperature, initial pH value, catalyst concentration and PMS dosage on the degradation of DNBP in NGA-4/PMS system were investigated. The catalytic degradation of DNBP followed the pseudo-first-order kinetic and the activation energy of the degradation reaction was calculated to be 31.3 kJ · mol⁻¹. The quenching experiments clearly demonstrated that SO₄ ^·− radicals served as predominant active species in the PMS activation catalytic process. The good applicability made the application of the prepared NGAs materials in PMS activation for removing organic pollutants more practical and feasible.