Enhanced conversion from H2O2 to 1O2 on Cu–N centers: Investigation of mechanisms and application in alkaline wastewater treatment

Heterogeneous Fenton-like systems using H2O2 as an oxidant have been extensively investigated in acidic and neutral conditions, but usually, they become ineffective under alkaline conditions. In this study, a cuprous graphitic carbon nitride material (Cu–CN) was prepared that can generate singlet oxygen (1O2) from H2O2. The results demonstrate that at pH 11, 95 % of 50 mg/L p-chlorophenol (4-CP) can be effectively eliminated within 120 min. Through semi-quantitative analysis and density functional theory calculations, it has been confirmed that 1O2 is the dominant reactive oxygen species in this system under alkaline conditions. The main pathway for 1O2 generation involves the formation of a complex between ·O2– and Cu(II)-N sites, and the subsequent intramolecular electron transfer. To enhance the stability and separation performance of this catalyst, polyethylene glycol (PEG) was employed as a binder to combine Cu–CN with Fe3O4. The terminal hydroxyl groups in PEG were cross-liked by metals, thus forming a solid and magnetic composite (CuFe@PEG). Compared to Cu–CN, CuFe@PEG exhibited remarkable performance with 93 % retention of its original capacity for 4-CP removal at pH 11. Furthermore, after seven cycles, the degradation efficiency only decreased by 6.36 %. This study introduces a novel approach for utilizing Fenton-like reactions in treating alkaline wastewater.