Biochar derived from spent mushroom substrate for efficient atrazine removal in aqueous solution

Given its extensive global usage and environmental persistence conferred by the stable triazine ring structure, the frequent detection of atrazine (ATZ) in the environment poses ecological and health risks. Spent mushroom substrate (SMS), as a widely available and low-cost agricultural waste, and its lignocellulosic composition and inherent porosity are conducive to generating highly aromatic and porous biochar structures for adsorbing ATZ. This study pioneeringly prepared biochar (BC) and acid-treated BC derived from SMSs of Pleurotus ostreatus, Oudemansiella apalosarca, and Lentinula edodes) via pyrolysis at 800 °C. Comprehensive characterization confirmed that the physicochemical properties of BC were significantly influenced by feedstock origin and acid treatment. Acid treatment improved specific surface area, porosity, and aromaticity, and alongside reduced hydrophilic ash content. Batch experiments indicated that acid-treated BC improved ATZ adsorption efficiency with removal rates increasing by 3.5–5.6 times, following the order of APBC (98.2 %) > AOBC (38.4 %) > ALBC (27.1 %). Adsorption kinetics and isotherms indicated heterogeneous surface interactions and multi-mechanism involvement. The elevated logKOC values of acid-treated BC reflected stronger affinity for ATZ on organic carbon-enriched sites. Mechanistic analysis quantified four dominant pathways with distinct contribution ranges of pore filling (2.2–42.4 %), hydrophobic partitioning (2.2–47.2 %), π–π electron donor-acceptor interactions (15.6–49.8 %), and hydrogen bonding (0.9–35.0 %). Thermodynamic studies revealed spontaneous, endothermic, and entropy-driven adsorption processes, and adsorption capacity of ATZ was favored under acidic and high-temperature conditions. These findings not only offer a solution for agricultural byproducts SMSs reuse into high-efficiency adsorbents through pyrolysis and acid modification but also establish a method to mitigate pesticide contamination in aqueous systems.