Enhanced photo Fenton-like AOP by N-doped and Cu–Fe loaded biochar for efficient sulfamethoxazole removal: Economic synthesis, catalytic, performance and mechanism

In this study, copper and iron-loaded biochar materials were innovatively prepared from wasted walnut green peel using a pyrolysis method with impregnation. Characterization results indicated that Cu and Fe impregnation not only enhanced biochar-specific surface area but also achieved a high degree of dispersion. The heterojunction of N elemental doping and Cu₂O/Fe₃O₄ in CuFe@BC-(1:1.5) demonstrated improved photo Fenton-like advanced oxidation processes (AOP). Under photolytic conditions, removal efficiencies for sulfamethoxazole (SMX) and total organic carbon (TOC) reached 92.25 % and 73.89 % at 30 min with neutral pH. The hydroxyl radicals (•OH) were the principal reactive species in the degradation of SMX, while x-ray photoelectron spectroscopy (XPS) disclosed that the combined transitions of Fe³⁺/Fe²⁺ and Cu²⁺/Cu⁺ enhanced redox cycling of the catalyst. CuFe@BC-(1:1.5) maintained a high removal rate after five recycling iterations, and the preparation process could be repeated more than five times. This work economically employed waste walnut green peel as a source of elemental carbon (C) and nitrogen (N), proposing a novel strategy to simultaneously achieve the dual objectives of waste reuse and pollutant removal.