Carbon-wrapped Bi12GeO20 composites for enhanced H2O2-assisted sonocatalytic degradation of tetracycline hydrochloride: Interfacial charge transfer and reactive oxygen species generation

Carbonaceous-coated Bi 12 GeO 20 (CB) composites were fabricated via an in-situ coating strategy to enhance H 2 O 2 -assisted sonocatalytic degradation of tetracycline hydrochloride (TC). Structural and microscopic characterizations revealed that the carbon coating suppressed crystal growth, reduced particle size, and established intimate interfacial contact with Bi 12 GeO 20 (BGO). Among all as-prepared samples, the composite 3% CB exhibited a favorable balance between catalytic performance and carbon loading, achieving over 90% TC removal within 40 min in the presence of H 2 O 2 under ultrasonic irradiation. Electrochemical analyses revealed that carbon modification significantly improved charge separation and reduced interfacial resistance. Fluorescence and ESR measurements revealed the generation of reactive oxygen species and highlighted the important role of hydroperoxyl radicals (·O 2 H) in the enhanced sonocatalytic process. Several degradation intermediates were identified, and possible transformation pathways were suggested involving hydroxylation, demethylation, and ring-opening. The enhanced performance was attributed to the synergistic effects of acoustic cavitation, carbon-mediated interfacial charge transfer, and H 2 O 2 activation. In addition, a probable sonocatalysis mechanism was eventually proposed. This work provides an interfacial carbon-engineering strategy for constructing efficient bismuth-based sonocatalysts for antibiotic-containing wastewater treatment.