Maximally Exploiting the Fe2+ at the Interface of Micro and Nano Bubbles in the Fenton-Coupled Micro and Nano Bubble System for Organic Pollutant Degradation

Heterocyclic compounds in high-salinity wastewater are highly resistant to degradation, posing significant treatment challenges. A hybrid micro-nano bubble Fenton system (FT-MNBs) was developed to enhance Fe2+ activation via interfacial effects. The FT-MNBs achieved a significantly higher indole degradation rate (0.0380 min−1) compared with micro and nano bubbles (MNBs) alone (0.0046 min−1) and conventional Fenton (0.01008 min−1). In real coking wastewater with a total dissolved solid (TDS) content of 3.266 g/L, FT-MNBs achieved COD removal efficiencies of 93.42% (initial COD 200 mg/L) and 72.54% (initial COD 10,000 mg/L), demonstrating excellent adaptability and efficiency in treating refractory high-salt organic wastewater. Electron spin resonance confirmed •OH as the main reactive species. Molecular simulations revealed that the MNB interface enhances the adsorption energy of Fe and H2O2, alters the Fe 3d orbital to better overlap with the O–O 2p orbital, and increases electron density—thus promoting O–O bond cleavage and free radical generation. The FT-MNBs not only enhances reaction kinetics but also offer scalability and energy efficiency, showing great potential for advanced industrial wastewater treatment.