Mixed Nanocomposites of Cu₂O and Mn₃O₄ to Activate Peroxydisulfate for Efficient Degradation of Tetracycline via Cu(III) Species

Copper-based catalysts have attracted increasing interest in wastewater treatment via peroxydisulfate (PDS) activation. However, little attention has been paid to developing cuprous oxide (Cu2O)-based catalysts. In this study, Cu2O–Mn3O4 nanocomposites were synthesized by a high-temperature coprecipitation method and served as PDS activators. The Cu2O–Mn3O4/PDS system exhibited extremely high removal efficiency of tetracycline hydrochloride, with initial rate constants 16 and 43 times that of the Cu2O/PDS system and Mn3O4/PDS system, respectively. The results from X-ray powder diffraction, X-ray photoelectron spectroscopy, linear sweep voltammetry, and H2 temperature-programmed reduction confirmed the transformation of CuO into Cu2O with the presence of Mn3O4 in the composite, and the strong Cu–Mn interaction facilitated high electron density for Cu2O, which made it was easy to donate electrons to PDS. Additionally, chemical quenching tests, Cu(III)–periodate complex identification, and Raman spectra were conducted to illustrate that Cu(III) was formed as the main species to attack the pollutants via two electrons transferring from Cu(I) to PDS. The study developed an effective Cu2O–Mn3O4 catalyst based on the strong interaction of two nanomaterials and provided new mechanistic insights for Cu(I)-triggered PDS activation.