The rainfall effect onto solidification and stabilization of heavy metal-polluted sediments

Rainfall makes impacts on process of solidification/stabilization and the long-term safety of solidified matrix. In this study, the effect of rainfall on solidification/stabilization process was investigated by rainfall test. The unconfined compressive strength (UCS) and toxicity characteristic leaching procedure (TCLP) were adopted to characterize the properties of S/S sediments before and after rainfall test. The samples cured for 28 days were subjected to semi-dynamic leaching tests with a simulated acidic leachant prepared at pH of 2.0, 4.0 and 7.0. Effectiveness of S/S treatment was evaluated by diffusion coefficient (D_e) and leachability index (LX). The results indicated that UCS decreased at maximum deterioration rate of 34.29% of the compressive strength after 7 days of curing, along with minimum rate of 7.89% after 28 days by rainfall, with >14 days referred. The rainfall had little effect on the leaching characteristics of heavy metals during the curing process. The simulated acid rain could make significant impacts on the leaching behavior of the heavy metals in the S/S materials. All cumulative fraction of leached heavy metals were less than 2.0 % which showed the good stabilization of cement. Furthermore, the calculated diffusion coefficient (D_e) for Cu was 1.28×10-11〖cm〗^2/s, indicating that its mobility was relatively low of heavy in S/S sediments. The calculated diffusion coefficient (Di) for Cd, Cu and Pb were 7.44×10-11, 8.18×10-12 and 7.85×10-12〖cm〗^2/s respectively, indicating that its mobility was relatively low of heavy metal in S/S sediments.
Methods
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