Magnetic biochar based on platanus leaves and iron sludge for persulfate activation and catalytic degradation of tetracycline

In this study, a novel magnetic biochar (BC-Fe n ), synthesized by one-step pyrolysis at 800 °C using platanus leaves and iron-containing sludge in different mass ratios, was used to activate persulfate (PS) for tetracycline (TC) degradation. Results show that BC-Fe 1:2 exhibited excellent degradation performance (91.4%), much better than the raw biochar (BC) (77.1%). And electron paramagnetic resonance (EPR) techniques demonstrated radical ( S O 4 · − , ·OH, O 2 · − ) and non-radical ( 1 O 2 ) pathways in BC-Fe 1:2 /PS, S O 4 · − was further proved to be the main active species by quenching experiments. Liquid chromatography-mass spectrometry (LC-MS) was utilized to identify the intermediates of TC and three possible degradation pathways were proposed. Additionally, the BC-Fe 1:2 was weakly affected by pH and the coexisting anions in wastewater, and could still remove 80% of TC in the third cycle experiment. This study provides a new idea for converting backwash iron-containing sludge from groundwater treatment plants into valuable catalysts, and provides new insights into the key role of low-cost magnetic biochar in PS activation. • Magnetic biochar (BC-Fe n ) was prepared with wastes of platanus leaves and iron sludge. • BC-Fe 1:2 /PS system could effectively degrade TC in a wide pH range. • S O 4 · − was the main active free radical in the BC-Fe 1:2 /PS system.