Stabilization/Solidification of Zinc- and Lead-Contaminated Soil Using Limestone Calcined Clay Cement (LC³): An Environmentally Friendly Alternative

• Main Authors: Vemula Anand Reddy, Chandresh H. Solanki, Shailendra Kumar, Krishna R. Reddy, Yan-Jun Du
• Format: Article
• Language: English
• Published: MDPI AG 2020-05-01
• Series: Sustainability
• Subjects: low carbon materials; heavy metal immobilization; sustainable remediation; environmentally friendly materials
• Online Access: https://www.mdpi.com/2071-1050/12/9/3725

Due to increased carbon emissions, the use of low-carbon and low-cost cementitious materials that are sustainable and effective are gaining considerable attention recently for the stabilization/solidification (S/S) of contaminated soils. The current study presents the laboratory investigation of low-carbon/cost cementitious material known as limestone-calcined clay cement (LC³) for the potential S/S of Zn- and Pb-contaminated soils. The S/S performance of the LC³ binder on Zn- and Pb-contaminated soil was determined via pH, compressive strength, toxicity leaching, chemical speciation, and X-ray powder diffraction (XRPD) analyses. The results indicate that immobilization efficiency of Zn and Pb was solely dependent on the pH of the soil. In fact, with the increase in the pH values after 14 days, the compressive strength was increased to 2.5–3 times compared to untreated soil. The S/S efficiency was approximately 88% and 99%, with increase in the residual phases up to 67% and 58% for Zn and Pb, respectively, after 28 days of curing. The increase in the immobilization efficiency and strength was supported by the XRPD analysis in forming insoluble metals hydroxides such as zincwoodwardite, shannonite, portlandite, haturite, anorthite, ettringite (Aft), and calcite. Therefore, LC³ was shown to offer green and sustainable remediation of Zn- and Pb-contaminated soils, while the treated soil can also be used as safe and environmentally friendly construction material.