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 ($\mathrm{t}=10\min$, 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 ${}^{29}\mathrm{Si}$ solid-state nuclear magnetic resonance (${}^{29}\mathrm{Si}$ NMR) were used to analyze the bonding linkage and the adjacent coordination structure of ${}^{29}\mathrm{Si}$ 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 ${\mathrm{Q}}^4(3\mathrm{Al})$ and ${\mathrm{Q}}^4(2\mathrm{Al})$ units compared with original LS, of which has more ${\mathrm{Q}}^4(1\mathrm{Al})$ and ${\mathrm{Q}}^4(2\mathrm{Al})$ 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.