One-step preparation and application of magnetic sludge-derived biochar on acid orange 7 removal via both adsorption and persulfate based oxidation

Magnetic sludge-derived biochar (MSDBC) was synthetized via a one-step co-precipitation method and conducted as a novel heterogeneous catalyst of persulfate (PS) activation for the oxidative removal of acid orange 7 (AO7). The porous structure and large surface area benefits the enrichment of the pollutant, while abundant Fe₃O₄ species and oxygen-containing functional groups promoted the generation of oxidative radicals, thus leading to the remarkable performance of AO7 removal. MSDBC also exhibited good stability with low iron leaching and consistent efficiency in reusability experiments. Radical scavenger experiments and electron paramagnetic resonance studies identified SO₄^•− and OH^• as the dominant oxidative radicals. The magnetic properties and feasible preparation method of MSDBC guaranteed the stability, which was evidenced in detail by the satisfactory reusability performance and low iron leaching during the degradation process. Distinguished from other PS based advanced oxidation processes, acidic conditions favored AO7 removal, while two halide irons Cl⁻ and Br⁻ could promote AO7 removal by MSDBC/PS system. The current outcomes demonstrated our approach of converting solid waste into stable, cheap and multifunctional biochar as a feasible resource utilization method, and was highly suggestive to the treatment of both wastewater and sewage sludge.