Groundwater contamination by heavy metals, particularly lead (Pb), is a major environmental and public health concern. Among the promising remediation techniques, Permeable Reactive Barriers (PRBs) have been widely applied for the in-situ removal of contaminants. However, limitations such as the undesirable cement setting behavior and the relatively low buffering capacity of natural zeolite restrict their broader application. This study investigates the feasibility of using a zeolite–cement–sand mixture with low cement as a PRB material for the removal of Pb from groundwater, with a specific focus on the effects of lead concentration on cement setting time and the long-term stability of the mixture.

Experimental tests were conducted by exposing zeolite–cement–sand mixtures to different concentrations of lead nitrate (5–100 cmol/kg-soil). The setting time of the cement was measured using a penetrometer, while lead retention capacity was quantified. Mineralogical changes were examined through X-ray diffraction (XRD) analysis to evaluate the stability of zeolite in the presence of lead ions.

The results demonstrated that the natural zeolite used in this study exhibited a maximum Pb retention capacity of 48.29 cmol/kg-soil, confirming its potential as an effective adsorbent in PRB systems. At very low cement contents (2–3 wt.% of zeolite), no cement setting was observed, whereas higher cement proportions initiated the setting process. The presence of Pb ions significantly delayed cement setting at all cement levels, with the delay being more pronounced at higher Pb concentrations. This phenomenon was attributed to the precipitation of Pb ions as lead hydroxide, which inhibited the progress of cement hydration reactions. XRD results confirmed that the crystalline structure of zeolite remained unchanged after exposure to Pb-bearing solutions, indicating its structural stability and resistance to dissolution—an essential factor for the long-term reliability of PRBs. Moreover, the inclusion of 3 wt.% cement improved the buffering capacity of the zeolite–cement–sand mixture. Samples containing 3% cement exhibited a buffering performance superior to that of smectite up to Pb concentrations of 80 cmol/kg-soil, highlighting their stronger resistance to acidification in contaminated environments.

Based on these findings, the zeolite–sand mixture with 3 wt.% cement is proposed as an optimal PRB material. It combines high Pb retention capacity and improved buffering ability while avoiding undesirable cement setting, thereby maintaining the permeability essential for PRB performance. Overall, this research confirms that the zeolite–cement–sand mixture with low cement content, particularly 3 wt.%, can serve as a sustainable, reactive, and permeable material for the remediation of Pb-contaminated groundwater.