Role of Nitrogen Dual Reaction Sites in N-Doped Graphene Aerogels for Synergistic Sulfamethoxazole Adsorption and Peroxymonosulfate Activation in Fenton-Like Process

Abstract

Persulfate-based advanced oxidation technology is widely used in water treatment, and the key is to develop catalysts showing excellent performance. In this study, an N-doped graphene aerogel with a three-dimensional macroscopic structure was prepared by chemically reducing graphene oxide using ethylenediamine and was used to activate peroxymonosulfate for sulfamethoxazole degradation. N-GA-2 has high pyridinic N content (5.84 at.%), and shows excellent catalytic performance in the activation of PMS. The SMX degradation rate was 94.11% within 90 min, and the first-order reaction rate constant was 0.0231 min−1. Furthermore, the adsorption of SMX on N-GA-2 was chemisorption, and the maximum adsorption capacity (qm) was 250 mg/g. Quenching experiments and electrochemical tests confirmed that the electron-transfer pathway was the main reason for SMX degradation. X-ray photoelectron spectroscopy and density functional theory revealed that pyridinic N, adjacent C atoms and electron-rich C=O functional groups were involved in the degradation of SMX. Specially, pyridinic N functioned as dual reaction sites for both SMX adsorption and PMS activation. The formation of SMX/N-GA-2* and N-GA-2/PMS* complexes, dominated by pyridinic N, enabled the completion of electron-transfer pathways. In addition, N-GA-2/PMS/SMX system demonstrated superior continuous catalytic performance in fluidized-bed experimental facility simulating practical applications, which can stably and sustainedly degrade SMX. This study focuses on the mechanism of electron transfer pathway induced by nitrogen dual reaction site in N-doped graphene aerogel and explores its potential application in engineering. This will provide basic theoretical support for the practical application of N-GA-2/PMS catalytic system.

Keywords: Nitrogen-doped graphene aerogel, peroxymonosulfate activation, Electron-transfer pathway, Nitrogen dual reaction site