A bifunctional graphene-based cathode for wastewater treatment in heterogeneous electro-fenton: Taking textile, old landfill leachate and simulated antibiotic wastewater as examples

Abstract

Enhancing heterogeneous electro-Fenton (EF) efficiency to deal with water pollution cannot avoid the limitation of Fe(II) regeneration and low efficiency of H2O2 production. Herein, we demonstrate an efficient and robust strategy for the growth of reduced graphene oxide (rGO) and iron layered double hydroxide (FeIIFeIII-LDH) composites on graphite felt (rGO-FeIIFeIII-LDH/GF). rGO-FeIIFeIII-LDH/GF shows accelerated Fe(II) regeneration, and excellent 2e− oxygen reduction reaction (ORR) activity. It was revealed by electrochemical measurements and density functional theory (DFT) calculations that rGO acted as an electron mediator, which enables a feasible fast electron transfer pathway (rGOHOMO(−0.99 eV) → FeIIFeIII-LDHLUMO(0.53 eV)) for Fe(II) regeneration. The 2e− ORR activity can be attributed to the electron transfer number (1.77–1.94), N-doping and Fe occupied the defect site of rGO. The heterogeneous (total Fe leaching meet GB 5740–2006) EF process enabled immediate activation of H2O2 into OH and O2−. Various wastewaters including simulated dye and antibiotic wastewater, textile effluent, old landfill leachate can be efficiently treated in 120 min. Moreover, after avoiding the influence of Cl− in the actual water body, the pollution load and toxicity of the effluent were more acceptable. These results provide new insights into the heterogeneous EF system constructed with carbon fiber-based bifunctional electrode for the treatment of various actual wastewaters.