Hydrometallurgical preparation of lithium aluminum carbonate hydroxide hydrate, Li2Al4(CO3)(OH)12·3H2O from aluminate solution

Abstract

Gamma-phase of the lithium aluminate (LiAlO2) is a ceramic powder used in molten carbonate fuel cells (MCFCs) and in other nuclear and ceramic applications. Upon exposure to water vapor and carbon dioxide at 25 °C, we have observed, that gamma-LiAlO2 converts to lithium aluminum carbonate hydroxide hydrate, Li2Al4(CO3)(OH)12·3H2O (LACHH) and Li2CO3. The conversion was detected by X-ray diffraction (XRD) and carbonate analysis. An equation for the conversion is given, and the morphology is determined by scanning electron microscopy. A high-temperature XRD study and thermogravimetric/differential thermal analysis (TGA/DTA) showed that LACHH decomposes at 250 °C. The decomposition products of LACHH and Li2CO3 react to form of alpha-LiAlO2 at first and then to gamma-LiAlO2 at temperatures of 650 and 1000 °C, respectively.This paper represents research of obtaining lithium aluminum carbonate hydroxide hydrate, Li2Al4(CO3)(OH)12·3H2O (LACHH) suitable for aluminothermic recovery of lithium. Thermodynamic calculations were carried out and the characteristics of the LACHH and compounds based on it were determined. Optimal conditions of the process (temperature, concentration of aluminum solution, duration of deposition) were investigated: running the process at 90 °C for 4 h with slow stirring at 60–90 rpm using an aluminum solution of 120 g/l Al2O3 (caustic module 3.8), the consumption of reagents for the preparation of aluminum solution is less by 25–40%. The maximum yield of LACHH is 94,25%. XRD analysis confirms the deposition of LACHH. Also the possibility of its implementation as a raw material in a combined process of the aluminothermic production of lithium “Synthesis–Reduction” was confirmed.These materials interlayered with free-electron compound, in addition to traditional methods of use, are highly perspective materials in various technologies: in the production of lithium, potential for use as a matrix of red phosphor, carbonate fuel cells are perspective in use in high-temperature power generating devices.