Chalcocite-catalyzed Fenton coupling with biodegradation for N,N-dimethylformamide treatment: insights into mechanism and cost-effectiveness

Abstract

A naturally abundant chalcocite was thermally modified for Fenton degradation of N,N-dimethylformamide (DMF), and the coupled biodegradation was explored to achieve greener and efficient treatment. The chalcocite oxide derived from 350 °C mainly consists of Cu₂S, CuO and Fe₂O₃, possessing an enlarged pore size and greater surface area. Under the optimum conditions (10 mM H₂O₂, pH 3.0, and a catalyst dosage of 2.0 g/L), the Fenton reaction achieved complete removal (100 %) of DMF within 5 min, demonstrating 100 times higher activity than pristine chalcocite. The promoted activity is attributed to the presence of S²⁻, which can accelerate the conversion of H₂O₂ into ROS by facilitating the redox reactions of Fe³⁺/Fe²⁺ and Cu²⁺/Cu⁺. The contribution of active species to DMF degradation follows the order of •OH > O₂^•− > ¹O₂, with the aqueous phase •OH playing a more prominent role in DMF degradation compared to the surface-bonded •OH. The Fenton degradation pathway analysis and mathematical calculations reveal that the intermediates are less toxic and more biodegradable, thus a Fenton-coupled biodegradation method was proposed. The batch and pilot experiments demonstrated that, compared with the Fenton reaction, this coupling method can reduce H₂O₂ consumption by 75 % and enable fast and cost-effective DMF removal. This work presents an effective method for treating bio-refractory organic compounds, thus providing an economically efficient treatment approach for industrial wastewater treatment.