Recycling paper packaging waste into Fe-biochar pellet catalyst for tetracycline degradation via peroxymonosulfate...

Recycling paper packaging waste into Fe-biochar catalysts is a promising strategy for resource utilization. In this study, a dissolution-regeneration method using a DMAc/LiCl system was employed to synthesis Fe-biochar pellet catalyst (Fe-WPBC) with corrugated cardboard as a cheap carbon precursor. The Fe-WPBC possessed a spherical cage-like hollow structure with millimeter-size dimensions, making it suitable for practical application. An impressive rate constant of 0.2452 min^-1 for tetracycline degradation via peroxymonosulfate activation was achieved, and Fe-WPBC showed high stability, maintaining close to 100 % tetracycline removal efficiency even after five cycles. Mechanistic insights were obtained through radical quenching, electron paramagnetic resonance, and electrochemical analysis etc. Both electron transfer path and SO₄·^- and O₂·^- dominated radical path concurrently existed. Possible degradation pathways were further proposed in combination with LC-MS and DFT calculations. Besides, toxicity simulations using T.E.X.T and ECOSAR programs showed that the degradation intermediates were less toxic than tetracycline. Finally, the practical application potential of Fe-WPBC was evaluated through a continuous flow reactor, which achieved a 99 % tetracycline degradation efficiency and maintained over 400 min. This study provides new insights into both the recycling of paper packaging waste and the development of pellet catalysts for pollution degradation.