Upcycling Guiera Senegalensis waste into biochar for sustainable amoxicillin removal from water

The increasing environmental pollution caused by antibiotics and solid waste presents a dual challenge. Biomass-based remediation strategies offer a promising approach to enhancing the circular economy, yet they remain a significant research challenge. In this study, a biochar with high adsorption capacity and catalytic activity was synthesized from agricultural waste (Guiera senegalensis) for the first time. The resulting biochar (GSBC) was applied in the adsorption and degradation of amoxicillin (AMX) through an advanced oxidation process (AOP) based on peroxymonosulfate (PMS) activation. The combined process (0.9 g/L GSBC/0.01 mM PMS) achieved AMX degradation rates of approximately 95.0 % and 90.0 % within 45 min in distilled and river water, respectively. Mechanistic studies using radical scavengers revealed that AMX removal occurred via both radical (HO^•, SO₄^{• –}and O₂^{• –}) and non-radical (¹O₂) pathway. The influence of inorganic salts (Cl⁻, NO₃⁻, CO₃²⁻, SO₄²⁻and PO₄³⁻) was also evaluated, with SO₄²⁻and PO₄³⁻ exerting the greatest inhibitory effects; however, removal efficiency remained around 80 % despite their presence. The GSBC/PMS system was further tested in various real water matrices, including river water, fountain tower water, aquaculture facility water, and tap water, demonstrating comparable efficiency to that observed in pure water, particularly in river water. Phytotoxicity assessments in different matrices also indicated better performance in river water. This study introduces a novel biochar precursor, promotes agricultural waste valorization, and contributes to the development of sustainable wastewater treatment within the framework of the circular economy.