Photocatalytic degradation of diclofenac using iron-doped hydrothermal carbonation carbon coupled with peroxydisulfate: Insights into reactive species contributions and degradation pathways via density functional theory.

The preparation of hydrothermal carbonation carbon (HTCC) from cellulose-rich reed biomass and its application in pollutant degradation effectively enable the resource utilization of reed biomass. However, the limited specific surface area and low porosity of HTCC restrict its application. Introducing transition metal elements into carbon materials shows great potential in the advanced oxidation processes (AOPs) for the remediation of organic-contaminated water. This study employed an acid etching-hydrothermal coupling strategy to synthesize iron-doped reed-derived HTCC (HTCC-Fe). A photocatalytic enhanced peroxydisulfate (PDS) activation system was established to achieve efficient degradation and ecotoxicity reduction of diclofenac (DCF). By designing biochar materials featuring furan ring structures and loading Fe active sites, the original electronic structure was altered, thereby increasing reactive site density and significantly enhancing PDS activation. Light irradiation accelerated PDS activation by generating photogenerated charge carriers that facilitated electron transfer, achieving over 95% DCF degradation within 90 min. Additionally, HTCC-Fe/PDS/visible light system exhibited good stability and environmental adaptability. Fukui function and surface electrostatic potential analyses precisely identified key reaction sites in DCF molecules, revealing preferential radical attack regions. Toxicity assessment using the Ecological Structure-Activity Relationships (ECOSAR) model confirmed reduced acute toxicity of degradation products. This study provides a theoretical framework and technical support for the precise treatment of organic pollutants in medical wastewater and the rational design of HTCC-based catalysts.