High-efficiency refractory organic pollutants removal boosted by combining heterogeneous electro-Fenton with electrochemical anodic oxidation over a broad pH range

Electrochemical anodic oxidation (AO) is a green and efficient treatment process for refractory pollutants degradation. The cathode in AO process generally serves as the counter electrode, and does not contribute significantly for pollutants removal. The heterogeneous electro-Fenton (EF) process uses the bifunctional catalytic material as cathode to produce H2O2 via 2e- oxygen reduction reaction and activate H2O2 decomposition to generate •OH for degrading pollutants. Herein, we investigated an integrated electrocatalytic process between heterogeneous EF and AO (EF+AO) to enhance refractory pollutants removal over a broad pH range without the production of iron-containing sludge. Total organic carbon removal of phenol by EF+AO was 98.2 % in 180 min under pH ∼5.9 and the applied current density of 1.0 mA cm−2, obviously higher than that of only EF (48.8 %) or AO (56.9 %). Significantly, EF+AO process can efficiently treat the actual coking wastewater that the chemical oxygen demand (COD) value gradually decreased from 312.3 mg L−1 to 47.8 mg L−1 with the low specific energy consumption of 14.0 – 25.7 kWh·(kg COD)−1. This process delivered excellent long-term durability in flow mode, retaining efficient degradation performance for phenol during 100 h of consecutive runs. Our results provide new insights into developing an energy-efficient electrocatalytic process for pollutants removal.