Leaching Properties of Heavy Metals in a Phosphate-Based Binder Stabilized Contaminated Soil

Abstract

Revegetation has emerged as a promising method in the rehabilitation of contaminated sites. As traditional binders (e.g. cement and lime) usually lead to high alkalinity and hardening in soils, it is necessary to develop new binders which are capable of both supporting plant growth and minimizing the leachability leaching of heavy metals. This paper presents an experimental study on the leaching properties of soil with coexisted Pb, Zn, and Cd contaminants sampled at an industrial contaminated site. The soil is solidified/stabilized using a new phosphate-based binder, SS-B. Batch-type leaching tests and a synthetic precipitation leaching procedure are conducted to evaluate the leachability of Pb, Zn, and Cd in SS-B stabilized soil. Frendlich sorption model is used to fit the experimental data and to obtain the sorption parameters of these three heavy metals. The retardation factor (R_d) of heavy metals in the SS-B stabilized soil follows the order of Pb > Zn > Cd. One-dimensional semi-dynamic leaching tests are performed to acquire observed diffusion coefficients (D^obs) of these three heavy metals. The results show that the values of D^obs of Pb, Zn, and Cd are 2.30 × 10⁻¹⁵ m²/s, 7.47 × 10⁻¹⁵ m²/s, and 2.51 × 10⁻¹⁵ m²/s respectively.