Solubility Experiments and Thermodynamic Modeling for the Quaternary System MgF₂–MnF₂–MnSO₄–H₂O and Its Subsystems at 298.15 K

The solubility data of the MgF2–MnF2–MnSO4–H2O quaternary system and its subsystems are crucial for the removal of magnesium ions from a MnSO4 aqueous solution as the MgF2 precipitate. However, these data recorded at 298.15 K have not been reported, except for the MnF2–MnSO4–H2O system. In this study, the solubility isotherms of the MgF2–MnF2–H2O, MgF2–MnSO4–H2O, and MgF2–MnF2–MnSO4–H2O systems at 298.15 K and MnF2 solubility in pure water at various temperatures were systematically measured. The results show that MgF2 solubility initially decreases sharply followed by a gradual decrease as the MnF2 concentration increases. MgF2 solubility rises with increasing MnSO4 concentration in pure MnSO4 and the MnF2-saturated MnSO4 aqueous solution. MgF2 solubility in the MnF2-saturated MnSO4 aqueous solution decreases to 2.3–6.5% of its value in the pure MnSO4 aqueous solution at a certain MnSO4 concentration. MnF2 solubility increases with increasing temperatures in the MnF2–H2O system. A Pitzer–Simonson–Clegg model incorporated in the ISLEC software was used to simulate and predict the solubility curves of the MgF2–MnF2–MnSO4–H2O quaternary system and its subsystems. The model satisfactorily represented the solubility data of the subbinary and subternary systems of the MgF2–MnF2–MnSO4–H2O quaternary system within the analysis error, except for the solubility isotherms of the Mg(Mn)SO4·7H2O, Mg(Mn)SO4·4H2O, and Mg(Mn)SO4·H2O solid solutions. The predicted solubility data of the MgF2–MnSO4–H2O system at 298.15 K agree well with the experimental data with a slight deviation of the MgF2–MnF2–MnSO4–H2O system. Based on the established model, the variation of MgF2 solubility curves with the addition of anhydrous MnF2 in MnSO4 aqueous solutions at different concentrations was predicted. The study provides theoretical guidance for removing magnesium ions from a MnSO4 aqueous solution via MgF2 precipitation

Phase Chemistry for Hydration Sensitive (De)intercalation of Lithium Aluminum Layered Double Hydroxide Chlorides

Lithium aluminum layered double hydroxide chlorides (LADH-Cl) have been widely used for lithium extraction from brine. Elevation of the performances of LADH-Cl sorbents urgently requires knowledge of the composition–structure–property relationship of LADH-Cl in lithium extraction applications, but these are still unclear. Herein, combining the phase equilibrium experiments, advanced solid characterization methods, and theoretical calculations, we constructed a cyclic work diagram of LADH-Cl for lithium capture from aqueous solution, where the reversible (de)­hydration and (de)­intercalation induced phase evolution of LADH-Cl dominates the apparent lithium “adsorption–desorption” behavior. It is found that the real active ingredient in LADH-Cl type lithium sorbents is a dihydrated LADH-Cl with an Al:Li molar ratio varying from 2 to 3. This reversible process indicates an ultimate reversible lithium (de)­intercalation capacity of ∼10 mg of Li per g of LADH-Cl. Excessive lithium deintercalation results in the phase structure collapse of dihydrated LADH-Cl to form gibbsite. When interacting with a concentrated LiCl aqueous solution, gibbsite is easily converted into lithium saturated intercalated LADH-Cl phases. By further hydration with a diluted LiCl aqueous solution, this phase again converts to the active dihydrated LADH-Cl. In the whole cyclic progress, lithium ions thermodynamically favor staying in the Al–OH octahedral cavities, but the (de)­intercalation of lithium has kinetic factors deriving from the variation of the Al–OH hydroxyl orientation. The present results provide fundamental knowledge for the rational design and application of LADH-Cl type lithium sorbents

Phase Chemistry for Hydration Sensitive (De)intercalation of Lithium Aluminum Layered Double Hydroxide Chlorides

Lithium aluminum layered double hydroxide chlorides (LADH-Cl) have been widely used for lithium extraction from brine. Elevation of the performances of LADH-Cl sorbents urgently requires knowledge of the composition–structure–property relationship of LADH-Cl in lithium extraction applications, but these are still unclear. Herein, combining the phase equilibrium experiments, advanced solid characterization methods, and theoretical calculations, we constructed a cyclic work diagram of LADH-Cl for lithium capture from aqueous solution, where the reversible (de)­hydration and (de)­intercalation induced phase evolution of LADH-Cl dominates the apparent lithium “adsorption–desorption” behavior. It is found that the real active ingredient in LADH-Cl type lithium sorbents is a dihydrated LADH-Cl with an Al:Li molar ratio varying from 2 to 3. This reversible process indicates an ultimate reversible lithium (de)­intercalation capacity of ∼10 mg of Li per g of LADH-Cl. Excessive lithium deintercalation results in the phase structure collapse of dihydrated LADH-Cl to form gibbsite. When interacting with a concentrated LiCl aqueous solution, gibbsite is easily converted into lithium saturated intercalated LADH-Cl phases. By further hydration with a diluted LiCl aqueous solution, this phase again converts to the active dihydrated LADH-Cl. In the whole cyclic progress, lithium ions thermodynamically favor staying in the Al–OH octahedral cavities, but the (de)­intercalation of lithium has kinetic factors deriving from the variation of the Al–OH hydroxyl orientation. The present results provide fundamental knowledge for the rational design and application of LADH-Cl type lithium sorbents

Phase Chemistry for Hydration Sensitive (De)intercalation of Lithium Aluminum Layered Double Hydroxide Chlorides

Lithium aluminum layered double hydroxide chlorides (LADH-Cl) have been widely used for lithium extraction from brine. Elevation of the performances of LADH-Cl sorbents urgently requires knowledge of the composition–structure–property relationship of LADH-Cl in lithium extraction applications, but these are still unclear. Herein, combining the phase equilibrium experiments, advanced solid characterization methods, and theoretical calculations, we constructed a cyclic work diagram of LADH-Cl for lithium capture from aqueous solution, where the reversible (de)­hydration and (de)­intercalation induced phase evolution of LADH-Cl dominates the apparent lithium “adsorption–desorption” behavior. It is found that the real active ingredient in LADH-Cl type lithium sorbents is a dihydrated LADH-Cl with an Al:Li molar ratio varying from 2 to 3. This reversible process indicates an ultimate reversible lithium (de)­intercalation capacity of ∼10 mg of Li per g of LADH-Cl. Excessive lithium deintercalation results in the phase structure collapse of dihydrated LADH-Cl to form gibbsite. When interacting with a concentrated LiCl aqueous solution, gibbsite is easily converted into lithium saturated intercalated LADH-Cl phases. By further hydration with a diluted LiCl aqueous solution, this phase again converts to the active dihydrated LADH-Cl. In the whole cyclic progress, lithium ions thermodynamically favor staying in the Al–OH octahedral cavities, but the (de)­intercalation of lithium has kinetic factors deriving from the variation of the Al–OH hydroxyl orientation. The present results provide fundamental knowledge for the rational design and application of LADH-Cl type lithium sorbents

Phase Chemistry for Hydration Sensitive (De)intercalation of Lithium Aluminum Layered Double Hydroxide Chlorides

Lithium aluminum layered double hydroxide chlorides (LADH-Cl) have been widely used for lithium extraction from brine. Elevation of the performances of LADH-Cl sorbents urgently requires knowledge of the composition–structure–property relationship of LADH-Cl in lithium extraction applications, but these are still unclear. Herein, combining the phase equilibrium experiments, advanced solid characterization methods, and theoretical calculations, we constructed a cyclic work diagram of LADH-Cl for lithium capture from aqueous solution, where the reversible (de)­hydration and (de)­intercalation induced phase evolution of LADH-Cl dominates the apparent lithium “adsorption–desorption” behavior. It is found that the real active ingredient in LADH-Cl type lithium sorbents is a dihydrated LADH-Cl with an Al:Li molar ratio varying from 2 to 3. This reversible process indicates an ultimate reversible lithium (de)­intercalation capacity of ∼10 mg of Li per g of LADH-Cl. Excessive lithium deintercalation results in the phase structure collapse of dihydrated LADH-Cl to form gibbsite. When interacting with a concentrated LiCl aqueous solution, gibbsite is easily converted into lithium saturated intercalated LADH-Cl phases. By further hydration with a diluted LiCl aqueous solution, this phase again converts to the active dihydrated LADH-Cl. In the whole cyclic progress, lithium ions thermodynamically favor staying in the Al–OH octahedral cavities, but the (de)­intercalation of lithium has kinetic factors deriving from the variation of the Al–OH hydroxyl orientation. The present results provide fundamental knowledge for the rational design and application of LADH-Cl type lithium sorbents

Solubility Isotherm Determination of the H₃BO₃ + RbCl + H₂O and H₃BO₃ + NH₄Cl + H₂O Systems at <i>T</i> = 273.15, 298.15, 323.15, 348.15, and 363.15 K and Thermodynamic Modeling

Highly concentrated boron is widespread in salt lake brine and nuclear wastewater. Treatment of these aqueous solutions involves the solubility of extensive boron-containing minerals. Recently, we concentrated on the temperature-dependent solubility of the H3BO3 + salt + water system. Here, we systematically determined the ternary solubility isotherms in the H3BO3 + RbCl + H2O and H3BO3 + NH4Cl + H2O systems at T = (273.15, 298.15, 323.15, 348.15 and 363.15) K, using an isothermal equilibrium method. The results showed that both ternary systems belonged to a simple eutectic case. The solubility isotherms consisted of the solubility branches of H3BO3(cr) and RbCl(cr) or NH4Cl(cr). Using a revised Pitzer–Simonson–Clegg (rPSC) model implemented in the ISLEC software, these ternary solubility data were represented by fitting the interaction parameters between H3BO3 and RbCl and H3BO3 and NH4Cl. With the help of these models, polythermal phase diagrams of the two ternary systems are predicted

Revisiting the Solid–Liquid Phase Equilibrium of the Li₂SO₄ + Rb₂SO₄ + H₂O and Li₂SO₄ + Cs₂SO₄ + H₂O Systems

Solid–liquid phase equilibrium data of the Li2SO4 + Rb2SO4 + H2O and Li2SO4 + Cs2SO4 + H2O systems are of importance for the design of alkali metal element extraction processes from sulfate leaching solution of lepidolite. Considering the serious inconsistency of the reported solid phases, especially double salts and solid solutions, phase diagrams of the two systems were reinvestigated experimentally. The results on the Li2SO4 + Rb2SO4 + H2O system at 298.15 K show five solids, i.e., Rb2SO4, Rb2SO4·Li2SO4, Rb2SO4·3Li2SO4·2H2O, Rb2SO4·5Li2SO4·4H2O, and a solid solution with the end members Rb2SO4·5Li2SO4·4H2O and Li2SO4·H2O. For the Li2SO4 + Cs2SO4 + H2O system at 298.15 K, the results also show five solids, i.e., Cs2SO4, Cs2SO4·Li2SO4, Cs2SO4·3Li2SO4·2H2O, Cs2SO4·5Li2SO4·4H2O, and Li2SO4·H2O, while there is no solid solution phase with the end members Cs2SO4·5Li2SO4·4H2O and Li2SO4·H2O. Moreover, the single crystal structures of Rb2SO4·3Li2SO4·2H2O and Cs2SO4·3Li2SO4·2H2O were determined

Phase Chemistry for Hydration Sensitive (De)intercalation of Lithium Aluminum Layered Double Hydroxide Chlorides

Lithium aluminum layered double hydroxide chlorides (LADH-Cl) have been widely used for lithium extraction from brine. Elevation of the performances of LADH-Cl sorbents urgently requires knowledge of the composition–structure–property relationship of LADH-Cl in lithium extraction applications, but these are still unclear. Herein, combining the phase equilibrium experiments, advanced solid characterization methods, and theoretical calculations, we constructed a cyclic work diagram of LADH-Cl for lithium capture from aqueous solution, where the reversible (de)­hydration and (de)­intercalation induced phase evolution of LADH-Cl dominates the apparent lithium “adsorption–desorption” behavior. It is found that the real active ingredient in LADH-Cl type lithium sorbents is a dihydrated LADH-Cl with an Al:Li molar ratio varying from 2 to 3. This reversible process indicates an ultimate reversible lithium (de)­intercalation capacity of ∼10 mg of Li per g of LADH-Cl. Excessive lithium deintercalation results in the phase structure collapse of dihydrated LADH-Cl to form gibbsite. When interacting with a concentrated LiCl aqueous solution, gibbsite is easily converted into lithium saturated intercalated LADH-Cl phases. By further hydration with a diluted LiCl aqueous solution, this phase again converts to the active dihydrated LADH-Cl. In the whole cyclic progress, lithium ions thermodynamically favor staying in the Al–OH octahedral cavities, but the (de)­intercalation of lithium has kinetic factors deriving from the variation of the Al–OH hydroxyl orientation. The present results provide fundamental knowledge for the rational design and application of LADH-Cl type lithium sorbents

Phase Chemistry for Hydration Sensitive (De)intercalation of Lithium Aluminum Layered Double Hydroxide Chlorides

Lithium aluminum layered double hydroxide chlorides (LADH-Cl) have been widely used for lithium extraction from brine. Elevation of the performances of LADH-Cl sorbents urgently requires knowledge of the composition–structure–property relationship of LADH-Cl in lithium extraction applications, but these are still unclear. Herein, combining the phase equilibrium experiments, advanced solid characterization methods, and theoretical calculations, we constructed a cyclic work diagram of LADH-Cl for lithium capture from aqueous solution, where the reversible (de)­hydration and (de)­intercalation induced phase evolution of LADH-Cl dominates the apparent lithium “adsorption–desorption” behavior. It is found that the real active ingredient in LADH-Cl type lithium sorbents is a dihydrated LADH-Cl with an Al:Li molar ratio varying from 2 to 3. This reversible process indicates an ultimate reversible lithium (de)­intercalation capacity of ∼10 mg of Li per g of LADH-Cl. Excessive lithium deintercalation results in the phase structure collapse of dihydrated LADH-Cl to form gibbsite. When interacting with a concentrated LiCl aqueous solution, gibbsite is easily converted into lithium saturated intercalated LADH-Cl phases. By further hydration with a diluted LiCl aqueous solution, this phase again converts to the active dihydrated LADH-Cl. In the whole cyclic progress, lithium ions thermodynamically favor staying in the Al–OH octahedral cavities, but the (de)­intercalation of lithium has kinetic factors deriving from the variation of the Al–OH hydroxyl orientation. The present results provide fundamental knowledge for the rational design and application of LADH-Cl type lithium sorbents

Phase Chemistry for Hydration Sensitive (De)intercalation of Lithium Aluminum Layered Double Hydroxide Chlorides

Lithium aluminum layered double hydroxide chlorides (LADH-Cl) have been widely used for lithium extraction from brine. Elevation of the performances of LADH-Cl sorbents urgently requires knowledge of the composition–structure–property relationship of LADH-Cl in lithium extraction applications, but these are still unclear. Herein, combining the phase equilibrium experiments, advanced solid characterization methods, and theoretical calculations, we constructed a cyclic work diagram of LADH-Cl for lithium capture from aqueous solution, where the reversible (de)­hydration and (de)­intercalation induced phase evolution of LADH-Cl dominates the apparent lithium “adsorption–desorption” behavior. It is found that the real active ingredient in LADH-Cl type lithium sorbents is a dihydrated LADH-Cl with an Al:Li molar ratio varying from 2 to 3. This reversible process indicates an ultimate reversible lithium (de)­intercalation capacity of ∼10 mg of Li per g of LADH-Cl. Excessive lithium deintercalation results in the phase structure collapse of dihydrated LADH-Cl to form gibbsite. When interacting with a concentrated LiCl aqueous solution, gibbsite is easily converted into lithium saturated intercalated LADH-Cl phases. By further hydration with a diluted LiCl aqueous solution, this phase again converts to the active dihydrated LADH-Cl. In the whole cyclic progress, lithium ions thermodynamically favor staying in the Al–OH octahedral cavities, but the (de)­intercalation of lithium has kinetic factors deriving from the variation of the Al–OH hydroxyl orientation. The present results provide fundamental knowledge for the rational design and application of LADH-Cl type lithium sorbents