LAUSR

Abstract Multi-walled carbon nanotubes (MWCNTs) have been used as catalysts or supports in many industrial applications. Therefore, we provide a low-cost and environmentally friendly route to synthesize MWCNTs from plastics and red mud (RM), which is beneficial to the disposal of waste-solid. This nano-materials (RM-CNTs) are used as novel catalysts for CGPO to remove SO2 and NO from flue gas. It was unexpected that RM-CNTs exhibit a different catalytic pathway from the RM catalyst (traditional Fenton-like reaction) result from the constrained nano-scale reaction in which Fe3O4/Fe0/Fe3C nanoparticles were encapsulated in MWCNTs. Combined with various quenching experiments and characterization analysis, the catalytic mechanism of RM-CNTs was clarified: (1) the in-situ carbothermal reduction increased the activity of the catalysts (Fe2O3→Fe3O4→Fe0→Fe3C); (2) Fe0 and Fe3O4 can form a metal-semiconductor interface with extremely low resistance which can accelerate electron transfer; (3) Fe3C as heterogeneous Fenton catalyst was rarely reported. The experimental results indicated that the activity of Fe-C bond was closely related to the type of carbon substrate during the formation process; (4) MWCNTs encapsulated Fe3O4/Fe0/Fe3C particles exhibited excellent catalytic activity, which was due to the existence of 1O2.