Enhanced degradation of tetracycline by membrane-confined catalytic reaction within Co₂CO₃(OH)₂/polyvinylidene fluoride

The limited mass transfer and sluggish reaction kinetics of traditional powder catalysts, as well as the trade-off between permeate flux and the removal efficiency of confined membranes, have significantly hindered practical application in wastewater treatment. In this work, a Co₂CO₃(OH)₂/polyvinylidene fluoride (Co₂CO₃(OH)₂/PVDF) confined catalytic membrane was constructed via a one-step hydrothermal method and used as a peroxymonosulfate (PMS) activator for tetracycline (TC) degradation. Surprisingly, Co₂CO₃(OH)₂/PVDF achieved 99.67 % TC removal under continuous flow-through mode with an extremely short hydraulic retention time of 5.4 ms and a high permeate flux of 7085.5 L m⁻²h⁻¹ bar⁻¹. Furthermore, the reaction kinetic constant was five orders of magnitude higher than that under batch mode (1.07 ms⁻¹ vs 0.37 min⁻¹), demonstrating the superiority of membrane-confined catalysis in enhancing TC removal. Reactive oxygen species (ROS) scavenging experiments, electron paramagnetic resonance (EPR) spectra and electrochemical measurement revealed that the oxidative degradation of TC was dependent on cooperative attack of radicals (SO₄•⁻, •OH and O₂•⁻) and non-radicals (¹O₂). Subsequently, three possible degradation pathways were proposed. This study highlighted the significance of confined effect and Co(Ⅱ) catalysis in synergistically promoting PMS activation for ultrafast TC removal, demonstrating the potential application of membrane-confined catalysis in industrial wastewater treatment.