Micro-nanobubble-assisted tetracycline degradation by biochar-supported FeCo-metal-organic framework derivatives/persulfate system

Abstract

Micro-nanobubbles (MNBs), as an emerging environmental-friendly technology, have shown great potential in enhancing advanced oxidation processes for water treatment. This study innovatively integrated MNBs with a biochar-supported cobalt-iron catalyst (CoFe/BC) and persulfate (PDS) system, creating a novel synergistic approach for tetracycline (TC) degradation. The CoFe/BC+PDS+MNB system achieved 95.63 % TC degradation efficiency under optimized conditions (50 mg/L catalyst, 30 mg/L TC, 400 mg/L PDS), outperforming the conventional system with half the catalyst. While CO₃^2- and HCO₃^- inhibited TC degradation, NO₃^-, H₂PO₄^-, and humic acid showed minimal interference. Mechanistic studies revealed that singlet oxygen (¹O₂), sulfate radicals (SO₄^•-), and hydroxyl radicals (•OH) were the primary reactive species. MNBs facilitated electron transfer between dissolved oxygen (DO) and CoFe/BC, while bubble collapse generated localized •OH hotspots. Electrostatic attraction between MNBs and CoFe/BC under acidic conditions (pH 3–6.2) improved DO conversion efficiency, while MNB stability at neutral-alkaline pH ensured sustained degradation (>91 % at pH 7–9). Despite pH sensitivity, the synergistic effect maintained efficient degradation across a broad pH range. This study demonstrates the potential of MNBs integration in persulfate-based advanced oxidation processes for water treatment applications.