Adsorption Characteristics of Stone-Bentonite Mixtures towards Zn: Equilibrium and Kinetic Tests

In the treatment of industrial polluted sites and the construction of landfill sites, anti-pollution barriers are usually used to prevent the diffusion of pollutants. In this paper, the adsorption characteristics of Zn ions by the rock-bentonite anti-pollution barrier were observed by means of static equilibrium and dynamic adsorption tests. The experimental results showed that the adsorption of Zn by stone chips—bentonite was close to the nonlinear Freundlich and Langmuir models. When the concentration of Zn ion is constant, the adsorption capacity increases with the increase in temperature. At a certain temperature, the adsorption removal rate decreases with the increase in concentration. Further study found that the adsorption of Zn from mixed soil was mainly an ion exchange process, and the adsorption mode of Zn from mixed soil was controlled by both intra-particle diffusion and membrane diffusion. Zeta potential, X-ray diffraction (XRD) and The Fourier Transform Infrared spectroscopy (FTIR) showed that with the increase in concentration, the mixed soil adsorbed more metal ions, and the thickness of the double electric layer decreased. Moreover, the adsorption of Zn2+ by bentonite was mainly interlayer adsorption and ion exchange. As an anti-pollution barrier material, the mixed soil of stone chips -bentonite can prevent the diffusion of pollutants, which has certain reference significance for engineering construction.