Activation of peroxymonosulfate over recyclable Co₃O₄/rice straw lignin-based carbon fiber flexible membrane for the degradation of organic pollutants

Heterogeneous composite catalysts have gained significant attention in recent years due to their cleanliness, high efficiency, and stable performance. However, the difficulty of recovery and high cost have always limited the development of heterogeneous composite catalysts. Herein, flexible lignin-based carbon fiber (LCF) membranes with easy recovery and low cost were prepared by electrospinning and carbonization using rice straw lignin waste and polyacrylonitrile (PAN). Following in-situ sedimentation and annealing treatment, Co₃O₄ nanoparticles were successfully anchored on the surface of LCF to achieve Co₃O₄/LCF composite membrane, which was utilized for activating peroxymonosulfate (PMS) with an impressive 83 % degradation efficiency of tetracycline (TC) within 30 min, the mineralization rate of TC reached 67 % within 90 min, and displayed exceptional degradation capabilities even with interfering substances. Based on the quenching experiments, electron paramagnetic resonance (EPR), electrochemical tests and X-ray photoelectron spectroscopy (XPS), both radical and non-radical pathways were involved for TC degradation, and non-radical pathway was identified as the primary route. Active sites such as C[dbnd]O, graphite N, pyridinic N, and the Co²⁺/Co³⁺ redox cycle played the crucial roles during the degradation process. Density functional theory (DFT) and high-performance liquid chromatography-mass spectrometry (HPLC-MS) analyses demonstrated the proposal of a plausible degradation pathway for TC.