Systematic review of lithium extraction from salt-lake brines via precipitation approaches

The efflorescence formation in metakaolin-based geopolymers is assessed in this study to provide a better understanding of the effect of the synthesis parameters. Efflorescence formation depends on the physical and chemical properties of geopolymers as well as the environmental exposure conditions. In this study a set of fifteen geopolymers were synthesized using different formulation. An accelerated test of efflorescence development is presented, where the grade of degradation was evaluated by visual observation and correlated to leaching potential, physical properties and microstructural features. The use of soluble silicate in the activator provides a denser and a less permeable matrix. This makes the extraction of free alkalis to the surface more difficult, reducing the extent of alkali leaching and therefore efflorescence. The use of K+ is also effective to reduce visible efflorescence. The efflorescence formation is predicted by the properties of the gel formed which are dependent on the mix proportioning.

/pdf/metakaolin-based-geopolymers-relation-between-formulation-3sj0qtaxti.pdf

Metakaolin-based geopolymers: Relation between formulation, physicochemical properties and efflorescence formation

Using a continuously operated laboratory plant for the catalytic hydrothermal gasification of biomass featuring a supercritical water salt separator we investigated the separation performance of three different binary type 2 salt–water mixtures and three ternary salt–water mixtures that consisted either of two type 1 salts or two type 2 salts dissolved in water. It turned out that a concentrated salt brine could not be recovered at the salt separator for the binary type 2 salt–water mixtures of Na 2 CO 3 , Na 2 SO 4 , and K 2 SO 4 . These salts precipitate as solids from supercritical water and thus lead to salt deposits inside the salt separator vessel. The ternary mixtures of two type 1 salts dissolved in water (KH 2 PO 4 –K 2 HPO 4 –H 2 O and three different mixtures of NaNO 3 –K 2 CO 3 –water) exhibited a separation performance similar to the binary solutions of type 1 salts that were discussed in Part 1 of this article. However, the mixtures showed separation performances that were different from the corresponding single salt solutions. It was also possible to recover a concentrated brine when feeding solutions containing the two type 2 salts Na 2 CO 3 and K 2 SO 4 . For these mixtures a certain amount of the type 1 salt K 2 CO 3 might form in supercritical water leading to salt separation efficiencies up to 95% for these mixtures.

Continuous salt precipitation and separation from supercritical water. Part 2. Type 2 salts and mixtures of two salts

The effects of various cations (Li+, Na+, K+, Rb+, Cs+, Mg2+, Ca2+, Sr2+, Ba2+, Mn2+, Co2+, and Ni2+) and anions (Cl−, Br−, I−, $$ {\text{NO}}_{3}^{ - } $$
 , $$ {\text{ClO}}_{4}^{ - } $$
 , $$ {\text{HCO}}_{3}^{ - } $$
 , and $$ {\text{CO}}_{3}^{2 - } $$
 ) on the molar absorptivity of water in the OH stretching band region (2,600–3,800 cm−1) were ascertained from attenuated total reflection infrared spectra of aqueous electrolyte solutions (22 in all). The OH stretching band mainly changes linearly with ion concentrations up to 2 mol·L−1, but several specific combinations of cations and anions (Cs2SO4, Li2SO4, and MgSO4) present different trends. That deviation is attributed to ion pair formation and cooperativity in ion hydration, which indicates that the extent of the ion–water interaction reflected by the OH stretching band of water is beyond the first solvation shell of water molecules directly surrounding the ion. The obtained dataset was then correlated with several quantitative parameters representing structural and dynamic properties of water molecules around ions: ΔG
 HB, the structural entropy (S
 str), the viscosity B-coefficient (B
 η
 ), and the ionic B-coefficient of NMR relaxation (B
 NMR). Results show that modification of the OH stretching band of water caused by ions has quasi-linear relations with all of these parameters. Vibrational spectroscopy can be a useful means for evaluating ion–water interaction in aqueous solutions.

Effects of Ions on the OH Stretching Band of Water as Revealed by ATR-IR Spectroscopy

The solubilities and physicochemical properties such as density and refractive index of the solution in the ternary systems KCl + MgCl2 + H2O and KCl + RbCl + H2O were investigated at 298.15 K using an isothermal evaporation method. The crystalloid forms of the solid phase were determined using chemical analysis and an X-ray diffraction method. On the basis of experimental data, the metastable equilibrium phase diagrams and the physicochemical properties vs composition in the ternary systems at 298.15 K were constructed. In the metastable phase diagram of the ternary system KCl + MgCl2 + H2O at 298.15 K, there are two invariant points, three univariant curves, and three crystallization fields corresponding to potassium chloride (KCl), magnesium chloride hexahydrate (MgCl2·6H2O), and a double salt carnallite (KCl·MgCl2·6H2O). In the metastable phase diagram of the ternary system KCl + RbCl + H2O, there are two invariant points and three crystallization fields corresponding to the single salts potassium chl...

Metastable Phase Equilibria in the Aqueous Ternary Systems KCl + MgCl2 + H2O and KCl + RbCl + H2O at 298.15 K

The stable phase equilibrium of mixed aqueous electrolyte system Li+, K+, Rb+, Mg2+//borate-H2O has been studied using the isothermal dissolution method at T = 348.15 K. The space diagram, the planar projection diagram (saturated with Li2B4O7), water content diagram, and diagrams of the physicochemical properties (densities and refractive indices) have been constructed based on the Janecke method. The crystallographic form of the solid phase at the quinary system invariant point was identified by the X-ray diffraction method. Results show that the quinary system belongs to a simple type without solid solution or double salt formed. The crystallographic form of borates formed in this work are Li2B4O7·3H2O, K2B4O5(OH)4·2H2O, RbB5O6(OH)4·2H2O, and MgB4O5(OH)4·7H2O. Under the condition of Li2B4O7 saturated, the crystallization area of salts decrease in the order of RbB5O6(OH)4·2H2O > MgB4O5(OH)4·7H2O > K2B4O5(OH)4·2H2O.

Stable Phase Equilibrium and Phase Diagram of the Quinary System Li+, K+, Rb+, Mg2+//Borate-H2O at T = 348.15 K

The metastable phase equilibrium of the quaternary system LiCl + KCl + RbCl + H2O at 348.15 K was done by using an isothermal evaporation method. The solubilities, densities, and refractive indices of the equilibrated solution were determined experimentally. On the basis of the measured data, the stereo phase diagram, the metastable phase diagram, the water content diagram, and the physicochemical properties versus composition diagrams were constructed. Results show that the quaternary system is of a complex type with the solid solution of potassium chloride and rubidium chloride [(K, Rb)Cl] formed at 348.15 K. The metastable phase diagram consists of two invariant points, five univariant curves, and four crystallization fields corresponding to single salts potassium chloride (KCl), rubidium chloride (RbCl), lithium chloride monohydrate (LiCl·H2O), and a solid solution of potassium and rubidium chloride [(K, Rb)Cl]. Salt RbCl has the largest solubility among the coexisting salts and presents the smallest ...

Ying Zeng

Papers

Metastable Phase Equilibria in the Aqueous Ternary Systems KCl + MgCl2 + H2O and KCl + RbCl + H2O at 298.15 K

Stable Phase Equilibrium and Phase Diagram of the Quinary System Li+, K+, Rb+, Mg2+//Borate-H2O at T = 348.15 K

Metastable Phase Equilibrium in the Quaternary System LiCl + KCl + RbCl + H2O at 348.15 K

Solid–liquid equilibria in the quinary system LiCl–KCl–RbCl–MgCl2–H2O at T = 323 K

Phase equilibria of CsCl-polyethylene glycol (PEG)-H2O at 298.15 K: Effect of different polymer molar masses (PEG1000/4000/6000)