LiNa3(SO4)2·6H2O: a lithium double salt causing trouble in the industrial conversion of Li2SO4 into LiOH

Lithium trisodium bis(sulfate) hexahydrate, LiNa3(SO4)2·6H2O was crystallized from aqueous solution at 298 K and the structure solved at different temperatures between 90 and 293 K. The structure is isomorphic with the corresponding molybdate and selenate double salt hydrate. It belongs to the non-centrosymmetric trigonal space group R3c (161). The temperature dependence of the lattice parameters has been determined. Further characterization by powder XRD and thermal analysis is reported.

Thermodynamic Analysis of Precipitation Characteristics of Rare Earth Elements with Sulfate in Comparison with Other Common Precipitants

The selective precipitation of rare earth elements (REEs) in acidic media often plays a key role in the effective extraction of these elements from various sources such as ores and recycling streams. In this study, the precipitation characteristics of REEs with sulfate, a frequently used precipitant, were carefully examined, and the results were compared with those of other precipitants, such as phosphate, oxalate, and fluoride/carbonate systems. Emphasis is given on various forms of precipitates, such as anhydrous sulfate, octa-hydrated sulfate, and sodium double salt, in which the sodium double salt was compared with the anionic double salt precipitation of the fluoride-carbonate system. It was found that anions such as Cl−, NO3−, and SO42− play an important role in the precipitation behavior, particularly through complexation with the dissolved REEs. In general, the effectiveness of precipitation follows the order of sodium double salt, a hydrated form of sulfate, and anhydrous sulfate. In this study, it was observed that the synergistic role of a double salt precipitation, either cationic or anionic, is frequently as effective as that of oxalate and phosphate, even in a low pH range.