Peroxymonosulfate activation by iron-rich biochar derived from sewage sludge digestate for sulfamethoxazole degradation: A rigorous examination of performance and mechanistic insights

The ubiquitous presence of sulfamethoxazole (SMX) within aquatic ecosystems coupled with the increasing production of solid waste digestate has emerged as a critical environmental challenge. This necessitates the development of efficient decontamination strategies and sustainable waste management approaches. This study introduces iron-doped biochar (FBC-600), synthesized via pyrolysis of sewage sludge digestate (SSD), as an effective catalyst for peroxymonosulfate (PMS) activation to degrade SMX in aqueous media, thereby transforming this waste byproduct into a valuable material for environmental remediation. The FBC-600/PMS system exhibited efficient SMX removal nearly complete within 90 min under optimized conditions. Notably, the system demonstrated robustness against pH variations and the presence of inorganic ions. Mechanistic investigations implicated singlet oxygen ( 1 O 2 ) and electron transfer as predominant reactive oxygen species (ROS). The catalytic performance was attributed to the synergistic interplay of C O, embedded iron, structural defects active sites on the FBC-600 surface. Moreover, the catalyst exhibited exceptional reusability and minimal iron leaching. The transformed products of SMX were examined through density functional theory (DFT) calculations and Liquid Chromatography-Mass Spectrometry (LC-MS). Concomitantly, the estimated toxicity of the identified intermediates was determined to be lower than that of SMX. This study highlights the potential of FBC-600 as a sustainable catalyst for SMX degradation by valorizing industrial bio-digestate according to zero-waste principles, which aim to minimize waste through strategies such as, reusing, reducing, recycling, refusing and composting. ● Sustainable FBC-600, iron-doped biochar from sewage sludge, enhances SMX removal. ● FBC-600 enables nearly complete SMX removal in 90 min. ● FBC-600/PMS system resists pH variations (3.2–11.4) with minimal iron leaching. ● Singlet oxygen ( 1 O 2 ) identified as main reactive oxygen species. ● Exceptional reusability aligns with zero-waste principles.