NH2-MCM-41 supported on nitrogen-doped graphene as bifunctional composites for removing phenol compounds: Synergistic effect between catalytic degradation and adsorption

Abstract

Nitrogen-doped graphene (NG) has received increasing attention as a metal-free catalyst in advanced oxidation processes (AOPs). In the present study, amino-functionalized mesoporous silica (NH2-MCM-41) was anchored onto NG surface and stacked NG sheets were unfolded with porous channels, thereby constructing unique catalytic and adsorption cells for removing p-cresol (p-CR) and bisphenol A (BPA). Compared with pristine NG, the nitrogen content of NG/NH2-MCM-41 composites increased from 3.61% to 4.83%, and the surface area enlarged from 98.03 m2/g to 193.93 m2/g. Meanwhile, the water contact angle reduced from 70.7° to 36.3°, indicating improved dispersibility of NG/NH2-MCM-41 composites in aqueous solution. Furthermore, modified NG in NG/NH2-MCM-41 composites exhibited 4.5-fold and 3.4-fold removal amount for p-CR and BPA, respectively, compared to that on pristine NG. Quenching experiments and characterization of reactive oxygen species (ROS) revealed that radical and nonradical mechanisms were involved in the catalytic process. Based on an investigation of interactions between NG/NH2-MCM-41, ROS and pollutants, a synergistic effect between catalytic degradation and adsorption was found and clarified by contrastive experiments. This work provided a strategy for modifying NG-based bifunctional composites and promoted the environmental remediation of aromatic pollutants by AOPs.