Preparation of lightweight ceramsite from solid waste lithium slag and fly ash

Lithium slag and fly ash are two types of solid wastes generated in large quantities in current industrial activities, which are often treated by storage methods because they contain harmful substances that cannot be used directly. According to the properties of the two solid wastes, this paper provided a novel eco-friendly utilization method of preparing them into small balls and roasting them at high temperature to produce lightweight ceramsite, and the properties and preparation mechanism of ceramsite were investigated. The results of the optimum conditions were as follows: the ratio of lithium slag: fly ash: kaolinite: albite, 40: 40: 10: 10; drying temperature 105 °C for 1 h; preheating temperature 500 °C for 15 min; sintering temperature 1240 °C for 20 min. Under these conditions, the apparent and bulk densities of ceramsite were 0.86 and 0.46 kg/m3, respectively, with a compressive strength of 1.76 MPa and a water absorption of 0.96%. Microstructural and crystalline phase analyses revealed that at the appropriate roasting temperature, the liquid phase on the surface of ceramsite and the generated gas acted to swell and form uniformly sized pores inside, and anorthite and mullite crystalline phases were formed. Thus, the prepared ceramsite was characterized by light weight, high strength, and low toxic leaching. This research filled the gap in the application of solid lithium slag in construction materials and innovatively combined lithium slag with fly ash to produce a new type of lightweight ceramsite. The use of solid waste to produce lightweight ceramsite provided a feasible way for harmless utilization and is of great significance to truly solve the environmental and reuse problems of solid waste.