Characteristics of Alkali-Activated Lithium Slag at Early Reaction Age

Lithium slag (LS), which is a byproduct of lithium salt production, has never been reported in alkaline activation studies. In this work, either characteristics of reaction products of alkali-activated lithium slag (AALS), such as phase compositions, microstructure, specific surface area, and water content, or the pore solution composition in AALS at an early reaction age is investigated. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to study the phases and microstructural morphology of AALS samples at typical reaction times (t=10 min, 30 min, 1 h, 3 h, 6 h, 12 h, and 24 h). In particular, the combination of Fourier transformation infrared (FT-IR) spectroscopy and Si29 solid-state nuclear magnetic resonance (Si29 NMR) were used to analyze the bonding linkage and the adjacent coordination structure of Si29 in LS and intermediate products of AALS. The results indicate that the Si─ O─ Si bond decreases while the Si─ O─ Al bond increases with alkaline activation reaction (AAR) enhancing and the chemical environment of Si preferred to Q4(3Al) and Q4(2Al) units compared with original LS, of which has more Q4(1Al) and Q4(2Al) units. Moreover, the composition of the pore solution was determined by inductively coupled plasma optical emission spectroscopy (ICP-OES). This paper reveals the evolution of AALS from multiple perspectives and may be of great significance for solid waste utilization.