Phase transformation of montebrasite for efficient extraction and separation of lithium, aluminum, phosphorus

Abstract

Montebrasite LiAlPO4(OH) is a high quality lithium extraction material with more than 8% Li2O content. The contents of Al and P as main component both exceed 16% while the chief impurity is SiO2, thereby the mineral purity is greater than 90%. In this paper, a process combining sulfuric acid baking and water leaching was proposed so as to realize the energy-efficient and comprehensive treatment of montebrasite and efficient extraction of Li, Al, and P. There are two main steps: (1) The montebrasite was heated and decomposed with sulfuric acid at 200 ℃. (2) The Li, Al and P in the baked slag were dissolved by water leaching. The X-ray diffraction(XRD) results of the baked slag prove that Li and Al are transformed into Li2SO4 and Al2(SO4)3 after decomposition by sulfuric acid. The only observed phase is SiO2 in the XRD patterns of leach residue, indicating that Li, Al and P are all transformed into soluble substances and leached by water after baking. The influence of baking temperature and baking time on the leaching rates of Li, Al and P was researched, and the leaching rates of Li, Al and P reached more than 96%. The novelty of the process lies in its low energy consumption, high comprehensive recovery rates of valuable elements and environmental friendliness.