Efficient utilization of multi-source solid waste to prepare the novel core-shell structured lightweight aggregates and its immobilization for volatile heavy metals

Owing to the low utilization rate, the overall amount of solid waste has been increasing every year. However, some solid waste contains hazardous heavy metals, especially volatile ones. If being managed improperly, they will cause severe threats to the environment and the health of humans. This work aims to safely utilize solid waste (contaminated soil, lithium slag, sewage sludge, and waste glass powder) to prepare the novel core-shell structured lightweight aggregate (CSLWA). An optimized ratio of CSLWA materials was designed based on Riley's Ternary Diagram. The physico-mechanical properties, microstructures, and phase compositions of the prepared CSLWA were analyzed, and the immobilization ability of CSLWA to volatile heavy metals was evaluated. The experimental results showed that the CSLWA produced from multi-source solid waste, possessing a density of 1.44-1.67 g/cm3 and a compressive strength of 8.1-9.73 MPa, showed excellent properties. Moreover, the volatilization rate of volatile heavy metals was reduced by at least 87% because of the shell of CSLWA. The leaching test results further demonstrated that the Zn and Cd could be effectively solidified in the CSLWA. This work thus provides an eco-friendlier approach to converting hazardous and industrial solid waste into high value-added materials and contributes to a more sustainable technique for producing lightweight aggregates.