Valorization of Waste Glass Toward NaA Zeolite for Pb(II) Removal from Water: Experimental and DFT Analysis

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Abstract Waste glass (WG) occupies land resources and threatens the environment due to its nonbiodegradability. In this study, NaA zeolite was synthesized from WG using a solvent-free method. The effects of reaction temperature, reaction time, and alkali–ash mass ratio on the crystallinity and specific surface area of NaA zeolite were examined through optimization experiments to determine the optimal reaction parameters. The adsorption performance and behavior of NaA zeolite toward Pb(II) were examined, and the adsorption mechanism was elucidated through density functional theory (DFT). Results showed the optimized NaA zeolite had a maximum crystallinity of 84.93%, a specific surface area of 67.96 m2/g, and abundant micropore and mesopore structures. The material exhibited excellent adsorption performance, achieving a Pb(II) removal efficiency of 98.68% and an adsorption capacity of 403.69 mg/g, its adsorption performance was 7.45 times that of the WG. Pb(II) removal involved chemical coordination and ion exchange with Na+. DFT calculations indicated lower activation energy (−9.2 kJ/mol) and stronger interaction of Pb(II) at Al–O than Si–O sites, with better thermodynamic stability. After six cycles, Pb(II) adsorption capacity remained 325 mg/g. Competitive adsorption results indicated that the adsorption capacity of the prepared NaA zeolite for heavy metal ions followed the order Pb(II) > Cu(II) > Zn(II). Meanwhile, the material maintains high Pb(II) removal efficiency in actual wastewater, demonstrating strong application potential. In addition, the solvent-free synthesis of NaA zeolite from WG offers significant environmental and economic advantages. Overall, this study provides both theoretical insight and practical support for the resource utilization of WG and its application in the treatment of Pb(II)-containing wastewater.

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