Bimetallic CoMn2O4 spinel as an effective catalyst for Peroxymonosulfate activation toward Perfluorooctanoic acid degradation

• Novel CoMn 2 O 4 spinel enables efficient PMS activation for PFOA breakdown. • Synergistic Mn–Co redox cycling drives radical generation and PFOA decay. • Achieved high PFOA removal (∼90 %) and defluorination (44 %) in mild conditions. • Revealed stepwise PFOA degradation via hydroxylation and decarboxylation. • Catalyst exhibits robust reusability and targets persistent organic pollutants. The widespread occurrence of perfluorooctanoic acid (PFOA) and its detrimental environmental impacts have become a major focus of global attention. This study focused on the synthesis of bimetallic CoMn 2 O 4 spinel by using the simple precipitation method followed by calcination at 550 °C. The peroxymonosulfate (PMS, HSO 5 − ) activation efficiency of as-synthesized catalyst has been investigated for PFOA degradation in PMS activated CoMn 2 O 4 catalytic system. Factors affecting the degradation efficiency were systematically examined. Under the optimal conditions (PMS concentration of 0.4 mM, catalyst dosage 0.2 g L −1 , and pH 5), the removal rate of PFOA (0.024 mM) was reached ∼ 90 % with a defluorination rate of 44 % after 180 mins at 30 °C. Bimetallic CoMn 2 O 4 spinel oxide exhibited excellent catalytic activity than single metal oxide of Mn and Co due to the formation of redox cycles between ≡Mn 2+ /≡Mn 3+ /≡Mn 4+ and ≡Co 3+ /≡Co 2+ and their synergistic interaction between Mn and Co species confirmed by various characterization techniques. The radical scavenger tests and electron paramagnetic resonance (EPR) results testified that • OH and SO 4 •− were the main reactive oxidation species (ROS) for the stepwise removal of PFOA. Additionally, five experimental runs were performed to prove the higher stability, reusability and superb performance with extremely low metal leaching. A marginal reduction in the removal of used catalysts was detected during four cycles, but simple calcination could recover the performance. Overall, unique structural features of CoMn 2 O 4 /PMS system confirmed the excellent catalytic performance in the remediation of emerging pollutants.