Enhanced visible light assisted peroxymonosulfate process by biochar in-situ enriched with γ-Fe2O3 for p-chlorophenol degradation: performance, mechanism and DFT calculation

In this study, a novel γ-Fe 2 O 3 /biochar (BF γ ) composite by a plant in-situ enrichment and one-step pyrolysis strategy was prepared, which was applied as a photocatalyst to activate peroxymonosulfate (PMS) for the degradation of p-chlorophenol (4-CP) under visible light irradiation (BF γ /PMS/Vis) system. The characterization results exhibited that γ-Fe 2 O 3 with localized carbon doping was evenly embedded in biochar during the pyrolysis. BF γ exhibited better photoresponse properties than biochar (BC) and γ-Fe 2 O 3 . The removal efficiency of this system for 4-CP reached 96.41% under optimal conditions. This system showed high removal efficiency with a wide pH range (3.0–13.0) and under conditions of different organic pollutants . It also showed strong resistance to interference with co-existing inorganic ions and humic acid (HA). Electron paramagnetic resonance (EPR) and radical scavenging experiments revealed that the reactive oxygen species (ROS) in this system included SO 4 - ·, ·OH, ·O 2 - and 1 O 2 . The density functional theoretical (DFT) calculations further revealed the promotion of localized carbon doping in γ-Fe 2 O 3 on electron transfer and photoresponse, including C-O bond (d=1.29 Å), C-Fe bond (d=1.80 Å) and band gap value (E gap < 0.72 eV). This study provides new insights into constructing environmentally-friendly catalysts and the possibility of the solid waste recycling for other wetland plants.