Experimental Research on Engineering Property of Heavy Metal-Contaminated Kaolinite

Abstract

Due to release and accumulation of industrial contaminants in natural soil in some regions, and the long-term interaction between leachate and clay which is adopted as isolation material of contaminants, the engineering property variation of clay soils after having been polluted by heavy metal ions gradually has drawn more and more attention of environmental geotechnical engineers. With relatively high chemical stability and low expansion coefficient kaolinite is widely distributed and usually used in engineering practice. In this research, Pb, Zn, and Cu-contaminated kaolinite specimens of controlled initial dry density and water content were manually prepared through static compaction. Then expansion capacity, unconfined compression, electrical resistivity and one-dimensional consolidation tests were conducted. It is found that the expansion capacity of contaminated kaolinite is influenced by the type and concentration of heavy metal ion. The unconfined compressive strength of heavy metal-contaminated kaolinite is decreased in a short period, but it may increase in a long term. Unconfined compressive strength of the same type of heavy metal-contaminated kaolinite will change with the contamination concentration. The electrical resistivity of kaolinite would be decreased when contaminated by heavy metal ions. The higher the contamination concentration is, the lower the electrical resistivity will be. All the compression indexes of heavy metal-contaminated kaolinite become lower than that of the clean kaolinite, and it also depends on both the type of heavy metal and contamination concentration. For the three types of heavy metal ions, Pb has the greatest influence on the engineering property of kaolinite, while the effects of Zn and Cu are quite similar.

Effect of heavy metal contamination on the plasticity of kaolin-bentonite clay mixtures and an illite-smectite rich natural clay

“…The effect of adding single heavy metals to the clays tested here confirms what has been found in some previous studies [18,23,25,26].…”

“…The ion concentration and pH are therefore the two factors which most affect the properties of bentonite. Even though previous researches by Di Maio and Fenelli [4] among others found that kaolinite is little affected by cations in the pore fluid, Liu, et al [26] found that heavy metal contamination decreases the unconfined compressive strength, electrical resistivity, and compression indices of kaolinite in the short term. However, the UCS and expansion strain of kaolinite may increase in the long term.…”