Flotation behavior of oleate and dodecylamine as mixed collector for recovery of lithium and rubidium from low-grade spodumene tailings: Experiment, characterization and DFT calculation

Abstract

With the explosive growth of demand for lithium, low-grade spodumene tailings could be concerned as alternative resources to realize the supplying. In this paper, a batch flotation experiment was adopted and optimized using sodium oleate (NaOL) and dodecylamine (DDA) as mixed collector by the reverse flotation desilication for recovery of lithium and rubidium from low-grade spodumene tailings. A favorable indicator of Li2O grade of 5.10% with recovery of 62.99%, and Rb2O grade of 2.09% with recovery of 50.80% for the flotation concentrate was obtained. The difference in contact angle results between flotation concentrate (13.92°) and tailings (47.96°) proves that the mixed collector could efficiently separate quartz and spodumene. The zeta potential measurement and Fourier transform infrared (FT-IR) spectra reveal that the optimal mixed collector could improve the hydrophobicity of quartz via charge neutralization and act on the mineral surface mainly through physical adsorption. Density functional theory (DFT) calculation shows that Al atom as the active site in the optimized spodumene (110) surface could adsorb water molecules, forming a hydration layer that inhibits spodumene from adhering to bubbles. Mulliken's charge population analysis confirm that NaOL + DDA could enhance the flotation efficiency of quartz by increasing the polarity of functional groups.