The use of contaminated soil and lithium slag for the production of sustainable lightweight aggregate

The contaminated soil (CS) and lithium slag (LS) contain amounts of hazardous ingredients which may move into the ground water and local cropland. In order to prevent CS and LS from damaging the environment, an investigation on the utilization of CS and LS for the production of lightweight aggregate (LWA) was presented in this article. The basic properties of LWA were evaluated. Furthermore, the crystalline phases of the produced LWA were analyzed, and the microstructure of LWA was analyzed by X-ray micro-tomography. The experimental results showed that the LWA produced from the CS and LS had good performances with density of 0.5-1.5 g/cm3 and compressive strength of 1.0-8.7 MPa, which met the required standard of LWA. Meanwhile, it can be revealed that the LS can reduce the sintering temperature of LWA, thus exhibiting low energy consumption. The analysis of crystal phases indicated that the mineral compositions of LWA contained spinel phases, which provided a possibility for the solidification of heavy metals. In addition, the evaluation of environmental effect revealed the leaching concentrations of hazardous metals were much lower than the critical limits of nonhazardous materials. Finally, the economic benefits were analyzed in the entire production process of LWA, which indicated that using CS and LS to produce LWA can lower the raw material cost by 85-98%. This work will create a more eco-friendly and economical method for the management of solid wastes (CS and LS). Meanwhile, this study can provide theoretical basis for the sustainable production of LWA.