Exploration of solidification/stabilization law and mechanism of lead-contaminated abandoned clay under hydrothermal conditions

Lead is a common heavy metal pollutant in abandoned clay. Stabilizing lead-contaminated waste clay through hydrothermal technology is expected to achieve high-level stabilization of lead ions. This paper carries out experiments on the solidification/stabilization of waste clay with different lead contents under the hydrothermal condition (200℃, 12h), and studies the stabilization mechanism of Pb²⁺ and its influence on the compressive strength, bulk density, water absorption and other properties of the solidified specimens. The results show that the stability rate of Pb²⁺ over 99%, and its stabilization is mainly achieved through the generation of compounds such as CaPb(OH)₄, Pb(OH)₂, PbO. The hydrothermal reaction greatly improves the strength of the specimen, which is about three times higher than that of curing at room temperature for 28 days. But lead slightly reduces the strength of the specimen. This may be related to the inhibition of Pb²⁺ on the formation of tobermorite and xonotlite.