Efficient degradation of methyl orange in wastewater via bio‐electro‐Fenton system: optimization, pathway investigation and process evaluation

BACKGROUND The efficient and green technology of dye removal has been widely investigated. In this study, a bio‐electro‐Fenton system was used to degrade methyl orange (MO). For the system optimization, five experimental groups were detected, including pH (1–6), iron (Fe 2+ ) concentration (3–15 mmol L −1 ), airflow rate (0–20 mL min −1 ), external voltages (0.2–1.0 V) and initial MO concentration (20–100 mg L −1 ). RESULTS Optimal conditions of pH 3, Fe 2+ concentration 9 mmol L −1 , air flowrate 12 mL min −1 , external voltage of 0.6 V and MO concentration 60 mg L −1 were selected, resulting in a 92% efficiency. For the pathway investigation of MO degradation, under oxidization by ˙OH, demethylation, broken azo bonds and broken benzene ring structure were obtained. Intermediate products were predicted. For the system evaluation, energy consumption of 0.15–0.59 KWh was determined for 1 m 3 MO wastewater. The total cost of degrading MO wastewater could decrease to US$470.0 m −3 by adjusting operational time. CONCLUSION Considering the Fe 2+ regeneration and the low energy consumption, this bio‐electro‐Fenton system can be considered as one of the most environmentally‐friendly approaches for MO degradation; however, quantitative evaluation on sustainability needs to be further discussed via advanced assessment tools (such as life‐cycle assessment).