Solubility of Electrolytes in Organic Solvents: Solvent-Specific Effects and Ion-Specific Effects

Abstract

Salt solubility in organic solvents is of particular interest in industry, for example, for carbon capture and storage or utilization processes, battery technology, or biotechnology. Electrolyte thermodynamic models have been developed to reduce the experimental effort for the design of an electrolyte toward desired properties, for example, high solubility in an organic solvent. In this work, the solubility of nine salts (NaCl, KCl, CsCl, NaHCO 3 , KHCO 3 , CsHCO 3 , Na 2 CO 3 , K 2 CO 3 , and Cs 2 CO 3 ) in the organic solvents methanol, ethanol, and N-methyl-2pyrrolidone (NMP) was studied at temperatures between 288.15 and 348.15 K. These systems were chosen since the largest amount of experimental data points were available in order to ensure a broad set of data for high modeling accuracy. Experimental solubility data were collected from literature, and missing data were measured in this work by both ion-chromatography analysis and the all-gravimetric method. The thermodynamic solubility product K SP of the salts was determined at 298.15 K and 1 bar. These K SP values do NOT depend on the solvent; that is, once known, they can be used to predict the solubility in any solvent or solvent mixture. K SP requires that the solid form of the precipitating salt be the same in different organic solvents. Therefore, powder X-ray diffractometer measurements were carried out to investigate possible hydrate formation or solvate formation, and Karl Fischer measurements were used to validate the absence of water. The equation of state ePC-SAFT was applied to model salt solubility in organic solvents by accounting for concentration-dependent dielectric constants within Debye−Huckel theory and Born theory. The required K SP values of the salts were determined using experimental literature data on the salt solubility in water together with the corresponding mean ionic activity coefficients (MIACs) at saturation. The availability of K SP and the predicted MIACs allowed modeling of the salt solubility in organic solvents in excellent agreement with experimental data. Furthermore, solvent-specific analysis and ion-specific analysis revealed a non-intuitive behavior of salt solubility in the organic solvents. One example is that ionspecific effects of salt solubility in alcohols are not valid in other organic solvents such as NMP. Furthermore, in contrast to aqueous solutions, salt solubility in organic solvents does not depend linearly on the cation size. Thus, experimental rules of thumb cannot be applied, and the experimental effort to screen salt solubility in organic solvents can only be significantly reduced by theoretical approaches such as ePC-SAFT.

Chemical Insights into the Formation of Colloidal Iridium Nanoparticles from In Situ X-ray Total Scattering: Influence of Precursors and Cations on the Reaction Pathway

“…Previous Zeta-potential analysis of Pt NPs from a closely related synthesis suggests the presence of stabilizing negatively charged species on the NP surface, and CO ad is also expected to serve as stabilizer on the Ir NP surface. Moreover, due to the very close p K a values of MeOH (15.3) and water (15.7), most M + OH – is actually in the form M + CH 3 O – as ion-pairs in MeOH . Methoxy groups may thus also stabilize the NP surface.…”

“…Moreover, due to the very close pKa values of MeOH (15.3) and water (15.7), most M + OH − is actually in the form M + CH 3 O − as ion-pairs in MeOH. 53 Methoxy groups may thus also stabilize the NP surface.…”

Catalytic conversion of chitin as a nitrogen-containing biomass

“…93 One probable reason is low solubility of NaCl in the aprotic solvents. 94 Rapidly heating to a high temperature dissolves the salt for accelerating the desired reaction before side-reactions. Accordingly, we need an easy method that many researchers can synthesise and isolate 3A5AF for further studies.…”

Chemical insights on the formation of colloidal iridium nanoparticles from in situ X-ray total scattering: Influence of precursors and cations on the reaction pathway

“…Moreover, due to the very close pKa values of MeOH (15.3) and water (15.7) most M + OHis actually in the form M + CH3Oas ion-pairs form in MeOH. 53 Methoxy groups may thus also stabilize the NP surface. If assuming that the main reactions accounting for the reduction and stabilization of the Ir NPs are: 1) deprotonation of CH3OH, 2) reduction of Ir 3+ or Ir 4+ to Ir(0) through oxidation of CH3OH to CO2, 3) reduction of Ir 3+ or Ir 4+ to Ir(0) through oxidation of CH3OH to CO, and 4) stabilization of Ir NPs by Cl -, CO and CH3O -, the overall reaction for the three different precursor salts can be summarized as:…”