Using our recently proposed method to obtain salt and ion polarizabilities in aqueous solutions, we determine the polarizabilities of five salts (LiCl, NaCl, NaBr, KBr, and MgSO4) in water–acetonitrile, water–ethanol, and water–acetone solutions at eight different water–organic solvent compositions at the D-line of sodium (589.3 ± 0.1 nm). Setting Li+ as the reference ion, we determine the ion polarizabilities of Na+, Cl–, and Br– in binary liquid mixtures. Our results show that cation polarizability is nearly unaffected by solvent composition, but anion polarizability exhibits a nonmonotonic behavior with increasing mole fraction of the organic component in the liquid mixture. This suggests that ion polarizability in a solution is affected by the solvent. The results of salt and ion polarizabilities can be used as important reference data for physical chemistry, atmospheric science, and biophysics.
Binodal data of poly(propylene glycol) PPG 400 + salt ((NH 4 ) 2 SO 4 , MgSO 4 , and KCl) + H 2 O systems were determined at T = 298.15 K, and binodal data of PPG 400 + KAc + H 2 O system was determined at T = (298.15, 308.15, and 318.15) K. Moreover, the binodal curves were fitted to Merchuk equation, and the tie-lines were fitted to both the Othmer–Tobias and Bancroft equations. The effects of temperature and salts on the binodals and tie-lines of the investigated ATPSs were also studied. Finally, the salting-out ability of salts on the polymer was obtained by fitting the Setschenow-type equation to the tie-line data to derive a salting-out coefficient ( k S ) for each salt. For potassium salts, the relative effectiveness of the anions in inducing the phase segregation in ATPSs follows the Hofmeister series. The relative salting-out effectiveness of the sulfate salts is influenced by complexation of the cations by PPG.
The investigation of the leaching mechanisms of ion adsorption rare earth ores (IAREO) using MgSO 4 is significantly hindered by the complex mineral composition. In this study, the direct analogue of the natural IAREO sample, Y-kaolinite, was prepared and used to investigate the leaching mechanisms of rare earths from kaolinite under varying initial MgSO 4 concentrations and pH. The results of X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray absorption fine structure (XAFS) data indicate that the Y-kaolinite prepared exhibits a similar composition, micromorphology and coordination structure with nature IAREO sample. The coordination number and bond length of Y–O are 9.2±1.4 and 0.23±0.010 nm, respectively. The results of batch desorption experiments and sequential chemical extractions show that lowering the initial pH from 5.00 to 2.00 significantly enhances the desorption of rare earths from Y-kaolinite. Specifically, the additional desorption amounts are 0.52 mmol/kg for inorganic hydroxy Y (Hy-Y) and 0.40 mmol/kg for ion-exchangeable Y (Ex-Y). The enhancement mechanism was revealed by density functional theory (DFT) and Visual MINTEQ. The desorption of Hy-Y and Ex-Y is directly and indirectly enhanced by hydrogen ions, respectively. The desorption of Hy-Y is consistent with the dissolution behavior of the Y hydroxyl compound at lower pH. The desorption of Ex-Y is promoted by [Al(H 2 O) 6 ] 3+ released from Hy-Al by hydrogen ions. Additionally, when the concentration of MgSO 4 is 100 mmol/L and initial pH is 2.00, the desorption rate of rare earths is 87.1%, while the adsorption rate of magnesium is 63.1% and the stoichiometry ratio of Y 3+ to Mg 2+ is 1.04, which indicates that adequate hydrogen ions reduce the consumption of MgSO 4 and enhance the leaching of rare earth. These finding provide valuable insights into optimizing the selective leaching of rare earths from IAREO.
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