Fe-Mo bimetallic-doped mulch-straw based biochar activating peroxodisulfate for efficient degradation of antibiotics in water

The advanced oxidation processes (AOPs) employing bimetallic catalysts for peroxodisulfate (PDS) activation has attracted considerable attention. A novel composite, polyethylene mulch-sorghum straw biochar (Fe-Mo 0.1 /N-PSC), was synthesized via hydrothermal activation, co-impregnation, and high-temperature pyrolysis to enhance catalytic efficiency and facilitate agricultural solid waste valorization. In the Fe-Mo 0.1 /N-PSC/PDS system, this composite efficiently activated PDS, achieving 91.86 % tetracycline (TC) removal within 3 minutes, with a pseudo-first-order rate constant of 0.1426 min⁻¹ , surpassing comparable catalytic systems. The influences of PDS concentration, catalyst dosage, pH, and temperature on TC degradation were systematically investigated. X-ray photoelectron spectroscopy indicated that the reactive Mo 4 + promoted the cycle of Fe²⁺/Fe³ ⁺, accelerating reaction kinetics. Quenching and electron paramagnetic resonance analyses confirmed the generation of radicals (•OH, SO₄•⁻, O₂•⁻), which actively contributed to TC degradation. Additionally, the persistent free radicals derived from PE during hydrothermal activation further enhanced degradation efficiency. Liquid chromatography-mass spectrometry identified degradation intermediates, elucidating possible pathways and proving the toxicity of intermediates greatly reduced. The system exhibited excellent stability, maintaining over 75 % degradation efficiency after five cycles with minimal metal leaching, offering valuable insights for practical applications. This study highlights Fe-Mo 0.1 /N-PSC as an effective PDS catalyst and a sustainable strategy for agricultural waste reutilization.