## 3 Results and Discussion
### Effect of Zeolite Content on Adsorption Performance of Soil Mixtures  
(1) Ion removal rate  
The relationship between the adsorption and removal rate of Zn by 15% zeolite coping stone chip-bentonite-zeolite mixture and the adsorption time under different concentration conditions are shown in Figure 8a. The adsorption and removal rates of Zn\({}^{2+}\) by mixed soil were 63.49, 73.06, 80.29, 89.64, 94.89, and 95.23% at 0.25, 0.50, 1, 2, 6, and 24 h for the initial concentration of the solution of 10 mmol/L and 30 mmol/L, respectively, versus 45.93, 57.17, 67.18, 75.15, 83.01, and 83.22%. It can be seen from the graph that the removal rate of Zn\({}^{2+}\) adsorption by the mixed soil became larger with the increase of time and tended to be stable after about 6 h. After 24 h of adsorption, the adsorption and removal rate of Zn\({}^{2+}\) by the mixed soil remained the same with time, and it can be considered that the adsorption equilibrium was reached at this time. Therefore, the 24 h adsorption was selected as the equilibrium time for further experiment. Figure 8b shows the variations in the Zn\({}^{2+}\) adsorption-removal rate with the initial Zn\({}^{2+}\) concentration. For a given initial Zn\({}^{2+}\) concentration, this rate increases with increasing zeolite content. For example, for an initial Zn\({}^{2+}\) concentration of 30 mmol/L, the adsorption-removal rates for zeolite contents of 0, 12.50, 25, and 50% were 67.21, 73.98, 76.01, and 83.40%, respectively. In addition, as the initial Zn concentration increased, an increase in the zeolite content produced a more notable increase in the Zn\({}^{2+}\) adsorption-removal efficiency. As the initial contaminant concentration increased, the Zn\({}^{2+}\) adsorption-removal rate of the soil mixture tended to decrease overall. For example, the adsorption-removal rates for zeolite contents of 0, 12.50, 25, and 50% were 98.60, 99.00, 99.07, and 99.16%, respectively, for an initial contaminant concentration of 3 mmol/L. However, these values decreased to 62.58, 68.50, 73.31, and 78.18%, respectively, for an initial contaminant concentration of 50 mmol/L. Figure 7: Effect of simultaneous variation of ZnCl\({}_{2}\) concentration stone chip\(-\)bentonite\(-\)zeolite mixture zeolite admixture on leachate ion concentration. (2)  
Mixed earth ion adsorption rate  
Figure 8b shows the variations in the Zn\({}^{2+}\) adsorption concentration of the soil mixture with the initial contaminant concentration. An increase in the initial contaminant concentration causes an increase in the Zn\({}^{2+}\) adsorption concentration of the soil mixture. For a zeolite content of 0%, the soil mixture had adsorption concentrations of 261.95 and 406.64 mg for initial contaminant concentrations of 30 and 50 mmol/L, respectively. The addition of zeolite produced notable changes in the Zn\({}^{2+}\) adsorption concentration. For a given contaminant concentration, increasing the zeolite content produced an increase in the Zn\({}^{2+}\) adsorption concentration of the soil mixture. For example, for a contaminant concentration of 50 mmol/L, the soil mixture had Zn\({}^{2+}\) adsorption concentrations of 444.99, 489.32, and 508.04 mg for zeolite contents of 12.50, 25, and 50%, respectively, corresponding to increments of 9.53, 20.48, and 27.49%. (3) Adsorption model  
According to the equation for the adsorption of pollutants by mixed soil for model fitting, where the Langmuir model and Freundlich model fitting correlation coefficient R\({}^{2}\) is closer to 1 compared with [PERSON] and D-R isothermal adsorption models, indicating that the adsorption of Zn\({}^{2+}\) by mixed soil is more consistent with the [PERSON] model and [PERSON] model, and the fitting curves are shown in Figure 9 (the end of the curves in the figure all reached adsorption equilibrium). As can be seen from the figure, the unit adsorption amounts at different concentrations are consistent with each model.