The current research proposes a novel approach to fabricate multifunctional iron- and manganese-loaded biochar (FeMn/BC) through one-pot pyrolysis of FeCl₃- and KMnO₄-impregnated durian husks (DHs). Analytical results indicated the presence of 5.72 wt% Fe (Fe₃O₄ & Fe0) and 2.90 wt% Mn (MnO) within the biochar (BC) matrix. Regarding porous properties, FeMn/BC possessed a specific surface area (SBET) of 292 m²/g and a total pore volume (Vtotal) of 0.19 cm³/g. Accordingly, FeMn/BC was explored as a photo-Fenton catalyst for tartrazine (TZ) degradation. At pH 3.0, 200 ppm H₂O₂, and UV light, 0.50 g/L FeMn/BC treated 92.0% TZ (50 ppm) within 10 min of adsorption and 120 min of oxidation. In addition, FeMn/BC with a saturation magnetization (MS) of 5.13 emu/g could be separated from treated mixtures by external magnetic fields. Overall, the multifunctional FeMn/BC prepared from DH waste demonstrated its magnetic separability and efficacy in treating TZ.