Experimental Study on the Solidification of Heavy Metal Pb2+ in Fly Ash-based Geopolymers

Abstract

To promote the utilization of combustion by-products such as fly ash in green building materials and mitigate heavy metal pollution in the environment, fly ash-based geopolymers were prepared to immobilize lead ions (Pb²⁺). Systematic experiments were conducted to investigate the immobilization efficiency of fly ash-based geopolymers for Pb²⁺ and the mechanical properties of the geopolymer matrix. Furthermore, the microstructure of the geopolymer matrix and the intrinsic mechanism of Pb²⁺ immobilization were elucidated via X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). The results show that the optimal immobilization content of Pb²⁺ in fly ash-based geopolymers is 2.0% when both compressive strength and leaching concentration are taken into consideration. The immobilization of Pb²⁺ by fly ash-based geopolymers is achieved through the synergistic effects of chemical bonding and physical encapsulation.