Influence and microscopic mechanism of the solid waste-mixture on solidification of Cu~(2+)-contaminated soil

摘要

In this paper, two aspects of studies are carried out: (1) synthesis of solid waste-mixture solidifier by using red mud, calcium carbide residue, and phosphogypsum; (2) solidification behaviors of the solid waste-mixture in the presence of Cu2+ ion. The performance of solidified soil was assessed by performing mechanical, permeability, and microstructure tests on samples. The results show that solid waste-mixture can improve the strength, brittleness, and impermeability of the contaminated soil, while the effect of Cu2+ ion is completely opposite. Additionally, the dominant heavy metal form in the solid waste-mixture solidified soil is iron-manganese oxide. The addition of solid waste is more conducive to the transformation of heavy metals to a stable form. The leaching toxicity values of solid waste-mixture solidified soil all meet the relevant standard and the effect is better than that of cement. Besides, the heavy metal can be fastened in the solidified soil through the precipitation, absorption of calcium silicate hydrate (C-S-H), and ion exchange of ettringite (AFt). In sum, it implied that the solid waste mixture had a potential application for the solidification of Cu2+-contaminated soil.