Fe-doped biochar derived from waste sludge for degradation of rhodamine B via enhancing activation of peroxymonosulfate

The disposal and management of waste sludge is a considerable challenge for environmental protection and resource utilization. Herein, sludge-based biochar material loaded with nano-Fe3O4 (xS@Fe-y) was fabricated via hydrothermal carbonization process and employed as catalyst to activate peroxymonosulfate (PMS) for degrading organic dyes in wastewater. Benefiting from the proper iron content, porous structure and the good dispersibility of iron on the catalyst surface, the proposed 5S@Fe-500 catalyst not only exhibited excellent catalytic activity and durability in the activation of PMS to degrade Rhodamine B (RhB), which was almost completely removed in 10 min (50 mL 50 mg L−1), but also performed broad application prospects in pollutant degradation. More importantly, the free radical quenching test and electron spin-resonance spectroscopy (ESR) detection demonstrated that O2•-, SO4•-, OH and 1O2 were generated during the process of catalyst activation of PMS. Based on this, a possible reaction pathway for degrading RhB with the aid of 5S@Fe-500 was put forward. It is believed that this work offers a promising reuse method of converting the waste sludge to a high efficiency and low-cost nano magnetic catalyst to activate PMS for degrading refractory organic pollutants in aquatic surroundings. Waste sludge was transformed into Fe-doped biochar catalyst via green hydrothermal carbonization for organic dye degradation in wastewater. [Display omitted] •Waste sludge was transformed into Fe-doped biochar for organic dye degradation.•Active species in sludge biochar and doped magnetic iron exhibited synergistic effect.•Mechanism of RhB degradation by 5S@Fe-500 was coaction of O2-, SO4-, OH and 1O2.