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

To improve cathodic HO accumulation and Fe 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, HO 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 (K) also improved from 0.0073 s to 0.012 s at a rotational speed of 300 rpm. In addition, the microbubble-assisted cathode further improved the K to 0.047 s. The synergistic effect between the rotating and microbubble-assisted cathodes further intensified HO accumulation in MRTTC. Apart from HO promotion, the iron reduction rate was elevated because the newly formed O provided an additional reduction pathway for Fe 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.