Confined coordination-engineered Cu–Ni/biochar via mechanochemical synthesis for highly efficient and durable peroxymonosulfate activation in water purification

The poor dispersion and stability of metal-doped carbon materials prepared via conventional hydrothermal or calcination methods have limited their application in advanced oxidation processes (AOPs). Herein, inspired by a hot-spot-effect-triggered confined coordination strategy, we developed a coconut shell biochar-supported Cu–Ni catalyst (Cu–Ni@BC) for peroxymonosulfate (PMS) activation to degrade multiple antibiotics, including tetracycline hydrochloride (TCH), ciprofloxacin (CIP), and norfloxacin (NOR). The mechanochemical synthesis endowed the catalyst with a high specific surface area, uniform metal dispersion, and strong metal–support interaction, ensuring stable loading and excellent catalytic activity. Under optimal conditions, the Cu–Ni@BC+PMS system achieved 96.7% TCH removal within 30 min, markedly outperforming single-metal systems. Radical quenching experiments and EPR analysis identified O 2 •⁻ as the predominant reactive species, with additional contributions from •OH, ¹O 2 , and SO 4 •⁻, collectively indicating a synergistic radical/non-radical mechanism. The catalyst retained high activity over five cycles (TCH removal efficiencies of 97.1%, 96.0%, 92.7%, 86.9%, and 82.3%), with minimal Cu and Ni leaching. Toxicity evaluation confirmed significant detoxification of TCH and its intermediates. Moreover, the catalyst displayed high degradation efficiencies for CIP (95.7%) and NOR (85.6%), excellent performance in real wastewater, and strong anti-interference tolerance toward common inorganic anions, achieving 85.6–96.9% removal for diverse antibiotics and dyes. This study overcomes the performance bottleneck of traditional single-metal catalysts in PMS activation and provides new insights into designing efficient, stable, and sustainable bimetal–biochar catalytic materials.