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

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 CO 3 2- and HCO 3 - inhibited TC degradation, NO 3 - , H 2 PO 4 - , and humic acid showed minimal interference. Mechanistic studies revealed that singlet oxygen ( 1 O 2 ), sulfate radicals (SO 4 •- ), 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.