Synthesis of ZSM-5 molecular sieve from coal gasification fine slag and its adsorption mechanisms for Pb2+ in aqueous solution

Coal gasification fine slag (CGFS) is a solid waste generated from entrained-flow coal gasification, characterized by fine particles and rich in silicon and aluminum elements. Using CGFS as a raw material for the preparation of ZSM-5 zeolite enables the high-value utilization of coal-based solid waste, offering significant economic and environmental benefits. This study proposes a simple and economical hydrothermal synthesis process for ZSM-5 zeolite using CGFS as the raw material. First, impurities in CGFS were removed through acid washing, followed by the effective extraction of silicon and aluminum components using an alkaline solution. Finally, ZSM-5 zeolite with a specific surface area of 358 m2/g was successfully synthesized under hydrothermal conditions at 170 °C for 48 hours. Adsorption experiments demonstrated that the synthesized ZSM-5 zeolite exhibits excellent adsorption performance for Pb²⁺ in aqueous solutions. At 25°C, the removal efficiency for a 50 mg/L Pb²⁺ solution reached 83.7%, with an adsorption capacity of 104.625 mg/g. The adsorption process is primarily governed by chemical adsorption mechanisms such as surface complexation, precipitation, and ion exchange. The synthesized ZSM-5 zeolite shows promising potential for application in the treatment of lead-containing wastewater.