Sustainable carbonaceous material from mushroom logs for lead(II) immobilization: Structure, binding mechanism, and optimization

Lead (Pb) contamination poses serious risks to human health and ecosystems, underscoring the need for sustainable immobilization strategies. Here, a carbonaceous material derived from waste oak mushroom logs (OM) was investigated for Pb(II) removal, with emphasis on translating optimization into deployable operating conditions. Biochar produced at 500 °C (OM5) exhibited heterogeneous, multilayer adsorption and achieved a baseline capacity of 42.29 mg/g from equilibrium tests. Kinetics followed a pseudo-second-order model, consistent with chemisorption. To convert these findings into actionable set-points, response surface methodology (Box–Behnken) was applied using pH (3–7), adsorbent dosage (1.66–5.00 g/L), temperature (10–40 °C), and ionic strength (1–9 mM) as factors. The optimized condition—pH 4.55, dosage 1.66 g/L, 30.6 °C, and 1.0 mM KCl—yielded a predicted removal percentage of 90.74%. Equilibrium was approached within 48 h. Isotherms were better described by Freundlich ( R 2 = 0.810) than Langmuir ( R 2 = 0.723), indicating heterogeneous multilayer adsorption. These results demonstrate upcycling of a forest residue into a high-value water treatment material and, critically, provide a ready-to-use operating recipe for Pb(II) polishing under mildly acidic, low-salinity conditions. • Biochar from waste mushroom logs used for Pb(II) removal from water. • Freundlich isotherm and PSO kinetics indicate heterogeneous chemisorption. • RSM yields deployable set-points: pH 4.55, 1.66 g L⁻¹, 30.6 °C, 1 mM. • Optimized capacity 90.74 mg g⁻¹ (vs. 42.29 mg g⁻¹ baseline) at low ionic strength.