An activated carbon‐geopolymer composite (ACGC) was prepared by using fly ash as raw materials via a simple geopolymerization process for treating the Pb(II) contaminant in wastewater and soil. The phase composition, microtopography, pore structure, and surface groups of the composites were studied by X‐ray diffractometer, field emission scanning electron microscopy, X‐ray photoelectron spectroscopy, N2 adsorption‐desorption isotherm, and Fourier transform infrared spectroscope. It was discovered that there was a synergistic effect between geopolymer matrix and activated carbon (AC), that is, addition of AC particles could increase the pores in geopolymer while strong alkalis condition provided by geopolymer enhanced the contents of oxygenic groups of AC. When the composite was used as the adsorbent, the sample containing 20 wt% AC (40ACGC) showed the maximum adsorption capacity (319.72 mg/g), and its adsorption isotherm fitted the Langmuir model well, suggesting the monolayer adsorption of Pb2+ on the 40ACGC. The kinetics of Pb2+ adsorption on the 40ACGC belonged to the pseudo‐second‐order model, indicating that Pb2+ adsorption on the composite followed chemical adsorption. In addition, the 40ACGC sample showed excellent stabilization performance for Pb2+ in soil. This work offered a new thinking to the application of geopolymers into remediation of heavy metal‐polluted soil.

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