Abstract
Exogenous humus can change the content and migration activity of cadmium (Cd) in soil. Humic acid (HA) is an important soluble humus component in soil. In order to explore the relationship between cadmium pollution mechanism and ecological environment of humic acid in reclaimed soil, the characteristics of humic acid adsorbing cadmium in alkaline conditions were studied. This study employed reclaimed soil from the Huainan mining area, China. The adsorption and desorption characteristics as well as influence mechanisms on the heavy metal cadmium (Cd) were explored under the influence of HA. The results show that: (1) When Cd concentration was low (0.2–10 mg/L), HA had little effect on Cd adsorption and desorption in reclaimed soil. When the Cd concentration was high (15–80 mg/L), HA had a great influence on the adsorption and desorption of Cd in reclaimed soil. The addition of HA can inhibit the adsorption of Cd by reclaimed soil and effectively improve the desorption capacity of Cd by reclaimed soil. (2) The kinetic curves of Cd adsorption and desorption of reclaimed soil with added HA show that both processes (adsorption and desorption) include two stages: rapid reaction and slow reaction. The adsorption of Cd by reclaimed soil under the influence of HA was 18.18% lower than that of normal reclaimed soil, and the increase of Cd desorption was 50.29%. (3) The factors affecting the adsorption and desorption of Cd in the soil were analyzed with gray theory, and their importance can be ordered as follows: Cd concentration > HA concentration > pH > temperature. Considering the influence of HA, a multi-factor coupling function model of adsorption and desorption of Cd in soil is established. This model provides theoretical guidance for the scientific prediction and evaluation of Cd environmental pollution risks in soil and will be useful for developing a new solution for engineering remediation of high concentration Cd contaminated soil.
Highlights
Huainan mining area is one of China’s main coal production bases and a major engineering construction area (Zhang et al 2018)
The adsorption characteristics and action mechanism of Humic acid (HA) on Cu2+, Pb2+, and Cd2+ were studied and the results showed that the adsorption intensity of HA on heavy metals followed Cu2+ > Pb2+ > Cd2+ (Zhu et al 2008)
Typical reclaimed soil samples of Panyi Mine in Huainan mining area are taken as research object, and a multi-factor coupling model of Cd adsorption and desorption in reclaimed soil is established
Summary
Huainan mining area is one of China’s main coal production bases and a major engineering construction area (Zhang et al 2018). Studies on the adsorption and desorption characteristics, the main influencing factors, and multi-factor coupling model of HA on heavy metal ions in reclaimed soil are rare. Typical reclaimed soil samples of Panyi Mine in Huainan mining area are taken as research object, and a multi-factor coupling model of Cd adsorption and desorption in reclaimed soil is established. This model provides theoretical guidance for the scientific prediction and evaluation of the environmental pollution risk of Cd in reclaimed soil and for the application of remediation technologies for alleviating soil Cd pollution
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