Efficient degradation of clofibric acid by heterogeneous catalytic ozonation using CoFe2O4 catalyst in water

Highlights: • CoFe₂O₄ was prepared and evaluated in heterogeneous catalytic ozonation process. • Possible mechanism was elucidated by radical trapping and quantification of H₂O₂. • Main reaction intermediates were identified and a plausible degradation pathway was proposed. • The acute toxicity of treated clofibric acid solution was decreased to almost zero. • CoFe₂O₄/O₃ was applied for the removal of various contaminants of concern in natural water. CoFe₂O₄ (Cobalt ferrite, CF) nanoparticles were prepared, well characterized and applied as efficient solid catalyst in catalytic ozonation, named CF/O₃ process, for the removal of emerging organic contaminants (EOCs). The degradation and mineralization of clofibric acid (CA) in CF/O₃ process were dramatically enhanced in comparison with those under the O₃ system. Surface hydroxyl groups (HGs) were considered as an important factor for ozone decomposition and the reactive oxygen species (ROS) on the catalyst surface were mainly responsible for CA elimination. The contribution and formation of ROS, including hydroxyl radicals (^• OH), especially superoxide radicals (O₂^{• −}), singlet oxygen (¹O₂), and hydrogen peroxide (H₂O₂) were evaluated, and a rational mechanism was elucidated accordingly. Probable degradation pathway of CA was proposed according to the organic intermediates identified. The acute toxicity of the treated solution increased during the first 15 min and then declined rapidly and nearly disappeared as the reaction proceeded. In addition, acceptable catalytic performance of CF/O₃ can be obtained for the treatment of other EOCs and the treatment of natural surface water spiked with CA. This work presents an efficient and promising catalytic ozonation technique for the elimination of EOCs in complex water matrices.