Effective abatement of tetracycline in water by activation of peracetic acid by the copper oxide loaded on straw-derived biochar via the enhanced copper redox cycling

Peracetic acid based advanced oxidation processes have been widely applied in the treatment of antibiotics in the aquatic environments, in which the efficacy is constrained by the limited >Cu(II)/>Cu(I) redox cycling. Herein, the copper oxide loaded on straw-derived biochar (CuO@BC) is designed based on the superior electron transfer ability of biochar, which can significantly enhance the redox transformation from >Cu(II) to >Cu(I). The copper species in CuO@BC exists as monoclinic CuO crystals, and the biochar is rich in oxygen- and nitrogen-containing functional groups. The CuO@BC/PAA system can achieve TC removal rate of 98 % within 30 min of reaction. Within the pH range typical of real wastewater (pH = 5–9), this system maintains a high TC removal efficiency (>95 %), demonstrating excellent TC degradation performance. According to the radical quenching experiments, EPR analysis and product ion spectra, acetylperoxy radical and hydroxyl radical play key roles in TC degradation. >Cu(II) in CuO@BC acts as an active site to activate PAA, in which the redox cycle between >Cu(II) and >Cu(I) enhanced by the biochar continuously reacts with PAA. The abundant ketonic carbonyl and graphitic/pyrrole nitrogen in CuO@BC also serve as active sites, contributing significantly to the generation of singlet oxygen via a non-radical pathway for TC degradation. The CuO@BC/PAA system is applicable to various real water matrices. This study demonstrates efficient TC degradation based on the electron transfer capacity of biochar and copper valence cycling, highlighting the promising application potential of the system.