Synergistic effect of Fe and Co metals for the enhanced activation of hydrogen peroxide in the heterogeneous electro-Fenton process by Co-doped ZnFe layered double hydroxide

Heterogeneous electro-Fenton (EF) is a powerful technology for the removal of emerging organic pollutants from wastewater. However, the development of catalysts with high activity towards the production of •OH by decomposing H2O2 remains a challenge. Herein, Co-doped ZnFe LDH as a heterogeneous catalyst with 2D plate-like morphology was produced by a co-precipitation method. Co-doping increased the pore volume of ZnFe LDH from 0.188 cm3/g to 0.2711 cm3/g and pore diameter from 5.305 nm and 9.39 nm. EF process consisted of a hydrothermally activated graphite felt cathode and a platinum plate anode. The Phenazopyridine (PHP) removal efficiency of the EF process in the presence of Co-doped ZnFe LDH is twice that of the electrochemical process. Additionally, Co-doping increased the performance of ZnFe LDH from 60 % to 82 % due to a synergistic effect of redox couples of Fe2+/Fe3+ and Co2+/Co3+. The Co-doped ZnFe LDH/EF process achieved complete removal of PHP in real wastewater in 4 h and at natural pH. After 7 reuse cycles, the catalyst retained 91 % of its performance. The eight by-products of PHP were determined by GC-MS. This work provides a way sustainable approach for the efficient removal of organic pharmaceuticals from wastewaters.