Analysis of Heavy Metal Leaching Characteristics and Kinetic Mechanisms in Soils under Leaching Conditions

DOI: https://doi.org/10.62517/jes.202602209

Author(s)

Yaling Liu1, Zhihong Zhang1, Gailei Tian1,*, Jinkun Huang2, Xixin Lu2

Affiliation(s)

1Institute of Geotechnical and Underground Engineering, Beijing University of Technology, Beijing, China 2China Seventeenth Metallurgical Construction Group Co., Ltd., Ma'anshan, Anhui, China

Abstract

To investigate the release behavior of heavy metals from soils around acid mine‑metallurgy polluted areas under rainfall leaching conditions, this study systematically examined the cumulative release characteristics and kinetic mechanisms of three typical heavy metals Zn, Pb, and As through leaching experiments. Different pH values (4, 5, 7, 8) and rainfall intensities (20, 30, 50 mm/h) were set to analyze the release patterns of heavy metals. Kinetic release models were constructed using the first‑order kinetic equation, modified Elovich equation, double‑constant rate equation, and parabolic diffusion equation. Results showed that the pH of the leachate gradually increased from an initially low value with prolonged leaching time and eventually stabilized around 7.5, while electrical conductivity exhibited a rapid decline followed by a steady trend. The release of Zn, Pb, and As all demonstrated significant pH dependence. Under acidic conditions (pH = 4), the release amounts of all three heavy metals increased substantially, with Zn being the most sensitive to pH variation. The release of As also showed a noticeable increase under alkaline conditions (pH = 8). With increasing rainfall intensity, both the cumulative release amount and the initial release rate of heavy metals increased, with Zn and As being particularly influenced by rainfall intensity. Kinetic fitting results indicated that, except for the first‑order kinetic equation, the modified Elovich equation, double‑constant rate equation, and parabolic diffusion equation could all adequately characterize the release process, with the parabolic diffusion equation providing the best fit (R² > 0.99). This study clarifies the release characteristics and kinetic patterns of typical heavy metals in contaminated soils from mining areas under rainfall leaching conditions, offering important theoretical insights and parameter support for risk assessment and control of heavy metal migration in acid mine‑metallurgy polluted areas.

Keywords

Column Leaching; Heavy Metals; Rainfall; Release Behavior; Kinetics

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