Nitrogen self-doped layered porous Myriophyllum aquaticum biomass–derived biochar activated persulfate to efficiently degrade printing and dyeing wastewater

Biochar doped with heteroatom-like nitrogen could significantly improve its performance in several environmental applications. However, the preparation requires an additional nitrogen source, which influences its cost-effectiveness and impedes the practical applications. In the present study, the nitrogen self-doped biochar was prepared by using Foxtail algae (Myriophyllum aquaticum), which is a typical N-rich wetland plant as the raw material, without any modifications. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray electron spectroscopy (XPS) were used to characterize the morphology and crystal structure of the material. The biochar prepared at 800 °C (MBC800) was found to have a better porous structure, large specific area (1069.08 m²g⁻¹), and more elemental N (3.11%). Furthermore, the MBC800 was used in the persulfate-activated degradation of Acid Orange 7 (AO7; 400 mgL⁻¹), and about 97.42% of the removal rate was observed within 60 min when the MBC800 and PS dosages (MBC800/PS) were at 0.25 gL⁻¹ and 4 gL⁻¹ respectively. The radical trapping results indicated that amongst the free radicals (–OH•, SO₄•–, O₂•–) and non-radicals (¹O₂), the surface-bound hydroxyl radical (–OH•) of biochar played an important role, and the non-radical singlet oxygen (¹O₂) played a dominant role during the AO7degradation. The study namely provides a new way for the exploitation and utilization of Foxtail algae in preparing nitrogen-doped biochar for several environmental remediation applications.