• • ZSM-5 synthesized from CGFS achieved a high specific surface area of 358 m2/g, enabling superior adsorption performance for Pb2+ removal.
• • At 25 °C, the ZSM-5-1 sample achieved 83.7% removal efficiency for a 50 mg/L Pb2+ solution, corresponding to an adsorption capacity of 104.625 mg/g.
• • Pb2+ adsorption is spontaneous and endothermic, dominated by chemisorption mechanisms including surface complexation, precipitation, and ion exchange.
• • Increasing acid concentration during pretreatment enhances silicon extraction and impurity removal, while excessive alkali concentration reduces crystallinity and surface area, potentially inducing clinoptilolite formation.