Remediation of Lead-Contaminated Sand through Cerussite Formation and its Effects on Sand Shear Strength Properties

This study addresses the effect of CO2 syntesised carbonate minerals use in situ to remediate lead (Pb)- contaminated soil and their effect on the soil mechanical properties. A spiked sandy soil sample contaminated with 3,000 ppm of lead nitrate (Pb(NO₃)₂) was subjected to injection of hydroxide (NaOH) solution and CO2 gas, which resulted in the formation of lead carbonate (PbCO3) minerals, identified as cerussite by scanning electron microscope (SEM) and X-ray diffraction (XRD) investigations. After 8 hours, more than 99% of the lead was converted to lead carbonate and successfully separated from the soil, showing the high promise of using the proposed in situ synthesis method for lead-contaminated soil remediation. On the other hand, direct shear tests of the soil showed some small reduction in the peak angle of friction at 15% cerussite contents, presumably due to the increased fines content; however the peak angle of friction was still high. This finding is important as depending on the soil use after decontamination, good mechanical properties of the soil may be a primary requirement.