Preparation of Biochar-Supported Zero-Valent Iron/Iron Carbide Composites and Their Application in TCPA Removal

• • SL-FeC2O4-800 °C achieved 98% TCPA removal within 2 minutes across pH 3–9, demonstrating rapid kinetics and broad pH applicability critical for real wastewater streams with fluctuating pH. • • The composite maintained high activity over five cycles, with degradation efficiencies of 98.54%, 80.94%, 64.88%, 46.79%, and 40.36%, indicating a 59% loss after five uses—highlighting the need for regeneration strategies to extend catalyst lifespan. • • Mechanistic studies confirmed that TCPA removal involves biochar adsorption, direct reduction by zero-valent iron, and oxidation by ROS generated via oxygen activation, with surface-bound iron species playing a pivotal role in ROS formation—this multi-pathway mechanism enhances robustness against varying water chemistries. • • The synthesis uses activated sludge (waste biomass) and ferrous oxalate, offering a cost-effective and sustainable approach for producing high-performance iron-based composites, aligning with circular economy principles and waste valorization.