Electrochemically Catalytic Degradation of Phenol with Hydrogen Peroxide in Situ Generated and Activated by a Municipal Sludge-Derived Catalyst

With the rapid global urbanization, today's cities are facing an increasing pressure for the treatment of both domestic and industrial wastewaters. In this work, a proof-of-concept of "treating industrial wastewater using the sludge originating from domestic wastewater treatment for urban pollution control" was proposed. After one-step pyrolysis of the excess sludge from domestic wastewater treatment, a metal–carbon composite catalyst with a high H2O2-producing capacity (432 mg/h/g) was successfully synthesized. By application of the prepared material as a cathode catalyst in an electro-Fenton system, phenol (40 mg/L), a model pollutant in industrial wastewaters, was completely degraded within 40 min at a potential of 0.15–0.35 V (vs reversible hydrogen electrode) without dosing external iron. Meanwhile, approximately 60% of total organic carbon was efficiently removed by the electro-Fenton system within 4 h at 0.25 V, and the hydroxyl radicals were found to be the main oxidation agent for the phenol degradation. More importantly, the phenol removal efficiency remained at a high level (87%) and the released iron was low (0.8 mg/L) even after 10 cycles of reuse. Thus, an efficient and cost-effective integrated system for the treatment of both domestic and industrial wastewaters was successfully developed and validated. The results from this work are useful to establish a new sustainable pollution control scenario.