A microbubble-assisted rotary tubular titanium cathode for boosting Fenton’s reagents in the electro-Fenton process

To improve cathodic H2O2 accumulation and Fe3+ reduction synchronously in the electro-Fenton (EF) process, a microbubble-assisted rotary tubular titanium cathode (MRTTC) was designed for the first time. By utilizing this MRTTC, H2O2 accumulation improved by 4.05-fold, along with a 200% enhancement in iron reduction compared to the conventional EF process. This promotion is mainly attributed to a considerably higher oxygen mass transfer, which reduces the thickness of the adhered diffusion layer. The oxygen mass transfer coefficient (KLa) also improved from 0.0073 s-1 to 0.012 s-1 at a rotational speed of 300 rpm. In addition, the microbubble-assisted cathode further improved the KLa to 0.047 s-1. The synergistic effect between the rotating and microbubble-assisted cathodes further intensified H2O2 accumulation in MRTTC. Apart from H2O2 promotion, the iron reduction rate was elevated because the newly formed O2-• provided an additional reduction pathway for Fe3+ reduction in addition to the cathodic path. The effectiveness of MRTTC was confirmed by treating a benchmark organic pollutant, sulfamerazine (SMR), where approximately 100% SMR decay was obtained in 3 h. The results show that MRTTC is a novel and promising design in EF for antibiotic wastewater treatment.