Perdisulfate-assisted advanced oxidation of 2,4-dichlorophenol by bio-inspired iron encapsulated biochar catalyst

To improve advanced oxidation processes (AOPs), bio-inspired iron-encapsulated biochar (bio-inspired Fe⨀BC) catalysts with superior performance were prepared from iron-rich biomass of Iris sibirica L. using a pyrolysis method under anaerobic condition. The obtained compounds were used as catalysts to activate perdisulfate (PDS) and then degradate 2,4-dichlorophenol (2,4-DCP), and synthetic iron-laden biochar (synthetic Fe-BC) was used for comparison. The highest removal rate of 2,4-DCP was 98.35%, with 37.03% of this being distinguished as the contribution of micro-electrolysis, greater than the contribution of adsorption (32.81%) or advanced oxidation (28.51%). The high performance of micro-electrolysis could be attributable to the formation of Fe (Iron, syn) and austenite (CFe_15.1) with strong electron carrier at 700 °C. During micro-electrolysis, Fe²⁺ and electrons were gradually released and then used as essential active components to enhance the AOPs. The slow-releasing Fe²⁺ (K = 0.0048) also inhibited the overconsumption of PDS (K = -0.00056). Furthermore, the electrons donated from Fe⨀BC-4 were able to activate PDS directly. The electrons were enriched by the porous structure of Fe⨀BC-4, and the formation of the COFe bond in the π-electron system could also accelerate the electron transfer to activate PDS. Similar reactive oxygen species (ROS) were identified during the micro-electrolysis and AOPs, leading to similar degradation pathways. The higher does concentration of O₂^- generated during micro-electrolysis than during the AOPs also led to a greater dechlorination effect.