Native Iron-Rich Quince-Derived Biochar for Sustainable Sulfamethoxazole Removal from Wastewater

In this study, quince-derived biochar was employed as a sustainable and multifunctional material for the removal of organic pollutants through different treatment alternatives depending on the pH (natural or modified), including adsorption and electro-Fenton degradation processes. The biochar, obtained by pyrolysis (500 °C, 14 h) of quince (Cydonia oblonga) biomass, exhibited a high intrinsic iron content (1296 mg/kg), which contributed to its electroactive properties and catalytic potential. Batch experiments demonstrated highly efficient adsorption of the target pollutant, the antibiotic sulfamethoxazole, achieving a maximum retention capacity of 35.51 mg/g. Regarding the degradation pathway, the electrochemical treatment achieved significant degradation rates under mild operating conditions, reaching total removal in less than 90 min. Both treatment options, under their respective optimal conditions, were subsequently evaluated using tertiary wastewater from a wastewater treatment plant, achieving good removal efficiencies exceeding 60% within 120 min. Finally, the treated effluent under optimal conditions was subjected to an ecotoxicity assay using the microalga Raphidocelis subcapitata, confirming the effectiveness of the treatment and the absence of harmful effects on this key microorganism in the aquatic food chain. These findings highlight the potential of iron-rich quince biochar as a low-cost and environmentally friendly material for various water treatment applications. Moreover, the results provide a promising approach for valorizing agricultural waste with inherent metallic content in heterogeneous electro-Fenton.