Guo Yafei

Extraction of lithium from salt lake brine with triisobutyl phosphate in ionic liquid and kerosene

Three ionic liquids(ILs), namely, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide and 1-ethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl] imide with the triisobutyl phosphate(TIBP) and kerosene system were respectively used to extract lithium ion from salt lake brine with a high concentration ratio of magnesium and lithium experimentally. Results indicate that the highest extraction selectivity for lithium was obtained with IL 1-ethyl-3-methylimidazolium bis[(trifluoromethyl)-sulfonyl]imide. The effects of solution pH and phase ratio R(O/A) on the extractive step and the influence of acid concentration of the stripping solution and R(O/A) on the back extraction step were also investigated systematically. The single-step extraction efficiency of lithium ion was 83.71% under the optimal extraction conditions, and the single-step back extraction efficiency was 85.61% with a 1.0 mol/L HCl in 1.0 mol/L NaCl medium as stripping agent at R(O/A)=2. The liquid-liquid extraction mechanism and the complex of the ligand with lithium were proposed.

Solid and liquid metastable phase equilibria in the aqueous quaternary system Li + , Mg 2+ //SO 4 2– , borate-H 2 O at 273.15 K

The metastable phase equilibria of the Li+, Mg2+//SO42–, borate-H2O system at 273.15 K were studied using isothermal evaporation method. The dry-salt phase diagram, water-phase diagram and the physicochemical property diagrams of the system were plotted with the metastable solubility values and physicochemical properties corresponding to density, refractive index, pH value and conductivity. The dry-salt diagram was composed of four crystallizing zones[lithium sulfate hydrate(Li2SO4·H2O), epsomite(MgSO4·7H2O), lithium metaborate octahydrate(LiBO2·8H2O), and hungchaoite(MgB4O7·9H2O)], five univariant curves and two invariant points (Li2SO4·H2O+MgSO4·7H2O+MgB4O7·9H2O and Li2SO4·H2O+LiBO2·8H2O+MgB4O7·9H2O). Li2B4O7 converted into LiBO2 in solution. Comparing the metastable phase diagram at 273.15 K and stable phase diagram at 298.15 K for the system, the crystallized area of Li2SO4·H2O and MgSO4·7H2O became large, whereas, the other phase regions became small. The J(H2O) changes regularly with increasing J(SO42‒), and the physicochemical properties change regularly with the concentration of B4O72‒ increasing.

Metastable Phase Equilibrium in the Reciprocal Quaternary System LiCl+MgCl 2 +Li 2 SO 4 +MgSO 4 +H 2 O at 348.15 K and 0.1 MPa

The metastable solubilities and the physicochemical properties including density and pH of the reciprocal quaternary system(LiCl+MgCl2+Li2SO4+MgSO4+H2O) at 348.15 K and 0.1 MPa were determined using the isother-mal evaporation method. The dry-salt diagram and water-phase diagram were plotted based on the experimental data. There are five invariant points, eleven univariant curves, and seven crystallization zones corresponding to hexahy-drite, tetrahydrite, kieserite, bischofite, lithium sulfate monohydrate, lithium chloride monohydrate and lithium car-nallite. Comparison between the stable and metastable diagrams at 348.15 K indicates that the metastable phenome-non of magnesium sulfate is obvious, and the crystallization regions of hexahydrite and tetrahydrite disappear in the stable phase diagram. A comparison of the metastable dry-salt phase diagrams at 308.15, 323.15 and 348.15 K shows that with the increasing of temperature the epsomite crystallization zone disappears from the dry-salt phase diagram of 303.15 K, and a new kieserite crystallization zone is presented at 348.15 K. The density and pH in the metastable equilibrium solution present regular change with the increasing of Jänecke index J(2Li+), and the calculated densities using the empirical equation agree well with the experimental values.