Melamine enhancing Cu-Fenton reaction for degradation of anthracyclines

Melamine (MA) enhanced Cu-Fenton process was developed for the degradation of anthracyclines. Taking daunorubicin (DNR) degradation as an example, we found that the initial first-order apparent constant of Cu²⁺/MA/H₂O₂ system with a molar ratio of 1:8 for Cu²⁺:MA was 5.2 times higher than that of conventional Cu²⁺/H₂O₂ system. The in-situ reductive coordination between Cu²⁺ and MA facilitated the generation and stabilization of Cu⁺ species, thereby accelerating the rate-limiting step of Cu²⁺/Cu⁺ conversion and maintaining high levels of Cu⁺ during the degradation process. Moreover, pre-synthesized Cu⁺-MA complexes (e.g., CM-250) further enhanced the efficiency of the Cu-Fenton reaction by increasing both the Cu⁺ proportion and MA chelation. The apparent activation energy for DNR degradation in CM-250 mediated Fenton reaction (15.9 kJ mol^-1) was lower than that in systems involving Cu²⁺/MA (41.2 kJ mol^-1) and Cu²⁺ (65.6 kJ mol^-1). Enhanced generation of various reactive oxygen species (·OH,·O₂^-, and ¹O₂) was confirmed, with ¹O₂ playing a dominant role, significantly improving both degradation rate and mineralization degree for DNR. MA-enhanced Cu-Fenton process also offers a convenient alternative to effectively remove other anthracyclines and organic micropollutants, holding great promise for advancing advanced oxidation processes as well as practical large-scale degradation applications targeting multiple pollutants.