Effective removal of humic acid by lignite activated coke via activation of peroxydisulfate: Identification of the key structural parameters

Abstract

Carbon catalysts are becoming potential substitutes for metal catalysts, however, the high cost and low reusability of carbon materials limit their practical application. Lignite activated coke (LAC) can be used directly for activation of peroxydisulfate (PDS), yet the key structural parameters for such a process remains unclear. In this study, two LACs with great differences were investigated for the removal of humic acid (HA) via activation of PDS. LAC1 has a much lower surface area (238.0 m2/g) than LAC2 (937.7 m2/g), but it has a high-proportioned mesoporous structure with more oxygen functional group on the surface. However, LAC2 has more graphene-like lamellar micropores with low-density O/N group on the surface. Under optimum conditions, the degradation efficiency of both LAC can reach more than 95 %, along with the distinguishing evolution of adsorption and catalysis process. Removal of HA by LAC1 were attributed mainly to its excellent adsorption capacity, whilst LAC2 demonstrate a much higher PDS activation owing to its pore structure and surface chemistry. The main reactive oxygen species were 1O2, which was likely attributed to the existence functional groups including C–N = C and –CO as electron donors. Furthermore, prospects of the application of LAC-based carbocatalysts for persulfates application are also proposed. Overall, this study provides a simple and efficient catalyst for PDS-mediated environment restoration and deepen the mechanistic innovations in 1O2-based nonradical-led oxidative pathways.