Semi-dynamic leaching tests on leaching properties of MPC-solidified zinc-contaminated soil under acid rain environment

The semi-dynamic leaching tests are conducted to investigate the leaching characteristics of MPC- solidified/stabilized Zn-contaminated soil under the effect of acid rain, and the CEMI groups are added to compare with the MPC ones. The concentrations of Zn²⁺ in leachant and pH of leachant are measured. Thus the effects of the initial pH of leachant and the type of curing agent on the cumulative mass of leached Zn are determined. The results show that the effects of acid rain on the CEMI groups are much greater than on the MPC groups. The accumulated leached Zn mass at leachant pH of 2 is much larger than that at leachant pH of 4 and 7. Nevertheless, the difference of the accumulated leached Zn mass between leachant pH of 4 and 7 is marginal. The amount of Zn²⁺ release by samples updating the leachant is greater than that of the samples that have no updating leachant. The sample with M/P of 6∶1 is better than that of 3∶1 in the curing effect. The diffusion coefficient (D_e) of Zn is back-calculated by conducting theoretical analysis of the relationship between the leaching time and the leached mass ratio. The D_e at leachant pH of 2 is larger than that at leachant pH of 4 and 7. It is found that the values of D_e of Zn at leachant pH of 4 and 7 are very close. According to the above data, it can be known that the types of cement and pH values of acid rain have significant influence on the leaching properties of MPC-solidified zinc-contaminated soil under acid rain environment.