Abstract
Heavy metals such as Cu(II) are widespread in the environment, and the impact of heavy metals on the environment of soils depends on the ability of soils to immobilize these pollutants. It is necessary to investigate the mechanism of interaction between heavy metal and soil from a soil remediation perspective. In this study, a series of experiments were conducted to investigate the adsorption and desorption behavior of Cu(II) in silty clay. Several impact factors such as pH, organic matter, temperature, and coexisted ions Zn(II) were considered. It was found that the adsorption process reached equilibrium after 4 hours of the experiment, and the data can be fitted well by the Elovich model and the double-constant model for the kinetic sorption process. The isothermal adsorption results showed that the adsorption rate reached a peak value when the initial concentration was about 20 mg L−1. The decrease of H+ can increase the adsorption activity of Cu(II) and reduce the ability of the desorption of Cu(II) ions. The adsorption capacity of Cu(II) is less than the desorption capacity under the condition of strong acidity and low concentration of Cu(II). In addition, the adsorption capacity of the native soil on Cu(II) was larger than that of the soil with the removal of organic matter, while the opposite was true for the desorption capacity on Cu(II). The maximum adsorption of Cu(II) occurred at 35°C for this study, and the binding energy increased as the temperature increased. Thermodynamic analysis revealed that the adsorption process of Cu(II) was spontaneous and endothermic. The Freundlich, Langmuir, Temkin, and Henry adsorption models were used for analyzing the adsorption isotherm of Cu(II), and it was found that the Freundlich model agreed the best with the experimental data compared with other three models. The results of the competitive adsorption experiments indicated that the competitive capacity of Cu(II) was greater than that of Zn(II) in low-permeability media such as silty clay, and the existence of binary metals can weaken the adsorption force between the single metal and the soil surface.
Highlights
Many industrial activities such as metal plating, mining operation, industry fertilizer, metallurgy, manufacturing battery, and dyeing in textile industries introduce heavy metals into the environment via their waste effluents [1]
Desorption experiments have been conducted to evaluate the ability of soil to release heavy metal ions under certain conditions
Kinetic adsorption experiments are performed at 25°C, pH = 5.5; initial Cu(II) concentration is set to be 20 mgL−1
Summary
Many industrial activities such as metal plating, mining operation, industry fertilizer, metallurgy, manufacturing battery, and dyeing in textile industries introduce heavy metals into the environment via their waste effluents [1]. Clay is a typical highly weathered soil It is widely distributed all over the world and contains a great amount of Al and Mg oxides. Hasine et al [13] studied the role of clay properties in heavy metal ion sorption and desorption with a series of experiments and found that soil composition would greatly affect the sorption efficiency. The most important interfaces involved in heavy metal adsorption in soils are predominantly inorganic colloids [16] Heavy metal such as Cu(II) can be adsorbed into the soil and desorbed under certain conditions [17]. We will investigate competitive adsorption onto the silty clay for solutions containing binary-metal mixtures of Zn(II) and Cu(II), which coexist in Chenchao mining area. The results of this study will provide some theoretical insights for preventing contamination and remediation of the contaminated soil
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