Display omitted •Biochar-ferrospinel AFe2O4 nanocomposites were synthesized for PAA activation.•The applied AOP system efficiently degraded CBZ and other PhACs under mild conditions.•CH3C(O)OO radicals were identified the dominant active species for CBZ degradation.•Excellent stability and magnetic separability of biochar-CoFe2O4 were observed.•Mechanistic studies were performed using techniques such as In-situ ATR-FTIR. Peracetic acid (PAA)-based advanced oxidation processes (AOPs) are promising technologies for the efficient treatment of persistent contaminants in wastewater. In this study, three different magnetic biochar (BC)-ferrospinel AFe2O4 (A = Cu, Co, or Mn) nanocomposites were synthesized through a combined sol–gel/pyrolysis process for the activation of PAA to degrade carbamazepine (CBZ). The following order of efficiency was observed for CBZ degradation in the presence of PAA: BC-CoFe2O4 (100 %) > BC-MnFe2O4 (7 %) ≈ BC-CuFe2O4 (7 %). In addition, 0.8 mM PAA, 0.3 g/L catalyst, nearly neutral pH, and 333 K were identified as the optimal operating parameters for the degradation of 1 mg/L CBZ in the BC-CoFe2O4/PAA system. Mechanistic studies revealed that CH3C(O)OO radicals are the dominant active species for the degradation of CBZ in the BC-CoFe2O4/PAA system, and the continuous conversion of Co(II) to Co(III) in this system is responsible for the generation of these radicals. In addition, the water matrices (e.g., humic acid (20 mg/L), NaCl (0.05 M), and NaNO3 (0.01 M)) played negligible roles in the degradation of CBZ in the BC-CoFe2O4/PAA system. This system exhibited highly selective and reactive degradation of organic pollutants with electron-rich groups (e.g., CBZ (0.36 min−1), sulfamethoxazole (0.12 min−1), and diclofenac (0.28 min−1)). Furthermore, the degradation products of CBZ were identified, and possible degradation pathways and toxicity of these transformation products were proposed. The BC-CoFe2O4/PAA system demonstrated outstanding degradation performance in dynamic systems and real wastewater treatment applications. This study describes the performance of an efficient and easy-to-separate catalyst for the activation of PAA. This study facilitates the development and application of PAA-based AOPs for wastewater treatment.