Novel photo-electro-Fenton process with natural air diffusion electrode coating recycled Zn-Mn oxides/C from spent Zn-Mn dry battery: fast generation and activation of H2O2.

The development of photo-electro-Fenton (PEF) technology could significantly enhance the efficiency of pollutants degradation. However, the high costs of efficient electrodes and catalysts for generating and activating hydrogen peroxide (H2O2) constrained its industrial application. To address these challenges, a natural air diffusion electrode (NADE) was introduced and coated with recycled Zn-Mn oxides/C catalysts from spent Zn-Mn dry battery to fabricate the recycled Zn-Mn/NADE (rZM/NADE) cathode, for fast generation and activation of H2O2. NADE could generate H2O2 by atmospheric oxygen without aeration, and it exhibited a high H2O2 generation rate of 998.3 mg L-1 (29.35 mmol L-1) and Faraday efficiency (94.4%) at 10 min. With the recycled Zn-Mn oxides/C catalyst loaded at 3 mg cm-2 onto the NADE, over 94.8% of H2O2 was utilized after a 10-min treatment in PEF system, while the removal rate of tetracycline (TC) was more than 98.8%. The electron paramagnetic resonance (EPR) probe capturing and quenching experiments co-confirmed the multiple generation mechanisms of reactive oxygen species (ROS), which proved the synergistic effect of cathodic electro-Fenton, photo-Fenton and anodic oxidation processes. This work provided insights for further reducing costs and enhancing efficiency of photo-electro-Fenton technology.