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... tests were carried out to confirm the availability of this experimental method and apparatus. Electric conductivity of NaCl aqueous were tested out under different concentrations at 18°C firstly and then compared with the literature [24], seen in Fig. 4. The measured results and the reference data were closed to each other with an average relative error of ...
Citations
... It is worth noting that different forms of ion pairs and ion clusters in aqueous solutions affect some of the physical properties of the solution. The conductivity of a solution depends on the concentration of the free ions in the solution and their diffusion coefficients [65]. For example, with increasing of the concentration of NaCl in aqueous solution from very dilute to near saturation, the conductivity of the solution increases non-linearly and increases more slowly at higher concentrations [66]. ...
... This is because the free ions will be transferred to solvent-shared ion pairs or direct contact ion pairs or clusters. Different from the NaCl aqueous solution, in the LiCl aqueous solution from very dilute concentration to a near-saturated concentration, the conductivity increases first and then decreases [65]. The hydration number in aqueous LiCl solution is also very different with that in aqueous NaCl solution. ...
The local structure and molecular interactions of Li⁺ salt in aqueous solutions is important in many fields. However, whether solvent shared ion pairs and the direct contact ion pairs exist in aqueous LiCl solutions or not, and the details about these ion pairs are still under debate. Here, we proposed a novel IR ratio method. Using this method, the hydration spectra of Cl⁻ in LiCl, NaCl, and KCl aqueous solutions were measured from the diluted concentration to the highly concentrated solution. Hydration number of Cl⁻ from the hydration spectra was determined to be ~ 2 in the aqueous LiCl. These data demonstrated that about 3–4 Li⁺ replaced some water molecules in the first hydration shell of Cl⁻. As the concentration of LiCl increased, an abnormal increase in the hydration number was observed. This is because the water molecule that bridges Li⁺ and Cl⁻ in the solvent-shared ion pair are particularly stable, which was directly proven by the red shift of the hydration spectra of Cl⁻ in the O–H stretching region. All the hydration spectra and hydration numbers not only applied to uncover the solvent shared ion pairs and direct contacted ion pairs in LiCl aqueous solution, but also can be employed to the benchmark of force fields in the classical molecular dynamics simulations.
... The relative static permittivity of the mixed solvent, the electrolyte-free solution is calculated using the volume fraction mixing rule, as shown in eq 1. 82 This equation has been proven to be very accurate compared to experimental data. 82 (1) where n i is the mole number, V k pure is the pure component molar volume, and ε r pure, i is the relative permittivity of pure component i. The effect of the salt is taken into account using a mild salt-concentration dependence, as proposed in a previous study, 83 to ensure accurate extrapolation to nonaqueous solvents. ...
In this work, mixed-solvent mean ionic activity coefficients (MIAC), vapor-liquid equilibrium (VLE), and liquid-liquid equilibrium (LLE) of electrolyte solutions have been addressed. An extended literature review of existing electrolyte activity coefficient models (eGE) and electrolyte equations of state (eEoS) for modeling mixed solvent electrolyte systems is first presented, focusing on the details of the models in terms of physical and electrolyte terms, relative static permittivity, and parameterization. The analysis of this literature reveals that the property predictions can be ranked, from the easiest to the most difficult, in the following order: VLE, MIAC, and LLE. We have then used our previously developed eSAFT-VR Mie model to predict MIAC, VLE, and LLE in mixed solvents without fitting any new adjustable parameters. The model was parameterized on MIAC of aqueous electrolyte solutions and successfully extended to nonaqueous, single solvent electrolyte solutions without any new adjustable parameters by using a salt-dependent expression for the relative static permittivity. Our approach yields excellent results for MIAC and VLE of mixed solvent electrolyte solutions, while being fully predictive. LLE is significantly more challenging, and an accurate model for the salt-free solution is crucial for accurate calculations. When the compositions of the two phases in the binary salt-free system are accurately captured, then the electrolyte extension of our model shows a lot of potential and is currently among the best eEoS for LLE prediction in the literature.
... It is worth noting that different forms of ion pairs and ion clusters in aqueous solutions affect some of the physical properties of the solution. The conductivity of a solution depends on the concentration of the free ions in the solution and its diffusion coefficient [63]. For example, with increasing of the concentration of NaCl in aqueous solution from very dilute to near saturation, the conductivity of the solution increases non-linearly, and the conductivity increases slowly at higher concentrations [64]. ...
... This is because the free ions will be transferred to solvent-shared ion pairs or direct contacted ion pairs or clusters. Different from the NaCl aqueous solution, in the LiCl aqueous solution from very dilute concentration to a near-saturated concentration, the conductivity increases first and then decreases [63]. The hydration number are directly related to the micro-structure of hydration shell. ...
The micro-structure and molecular interactions of Li ⁺ salt in aqueous solutions is important in many fields. However, whether the solvent shared ion pairs and the direct contacted ion pairs exist in LiCl aqueous solutions or not, and the details about these ion pairs are still under debate. Here, we proposed a novel IR ratio method. Using this method, the hydration spectra of Cl ⁻ in LiCl, NaCl and KCl aqueous solutions were measured from the diluted concentration to the highly concentrated solution. Hydration number of Cl ⁻ from the hydration spectra was determined to be ~ 2 in the aqueous LiCl. These data demonstrated that about 3 ~ 4 Li ⁺ replaced some water molecules in the first hydration shell of Cl ⁻ . As the concentration of LiCl increased, abnormal increase in the hydration number was observed. This is because the water molecule that bridges Li ⁺ and Cl ⁻ in the solvent-sharing ion pair are particularly stable, which was directly proven by the red shift of the hydration spectra of Cl ⁻ in the O-H stretching region. All the hydration spectra and hydration numbers not only applied to uncover the solvent shared ion pairs and direct contacted ion pairs in LiCl aqueous solution, but also can be employed to the benchmark of force fields in the molecular dynamics simulations.
... As shown in Figure 1A, we demonstrated that 48 h dialysis with changes every 6 hours was enough to lower the electric conductivity of the permeate to that of deionized water. Even if it is an indirect measurement, this simple classical method allows the detection of lithium bromide with reproducible results [32,33]. ...
The development and evaluation of scaffolds play a crucial role in the engineering of hyaline cartilage tissue. This work aims to evaluate the performance of silk fibroin hydrogels fabricated from the cocoons of the Colombian hybrid in the in vitro regeneration of hyaline cartilage. The scaffolds were physicochemically characterized, and their performance was evaluated in a cellular model. The results showed that the scaffolds were rich in random coils and β-sheets in their structure and susceptible to various serine proteases with different degradation profiles. Furthermore, they showed a significant increase in ACAN, COL10A1, and COL2A1 expression compared to pellet culture alone and allowed GAG deposition. The soluble portion of the scaffold did not affect chondrogenesis. Furthermore, they promoted the increase in COL1A2, showing a slight tendency to differentiate towards fibrous cartilage. The results also showed that Colombian silk could be used as a source of biomedical devices, paving the way for sericulture to become a more diverse economic activity in emerging countries.
... 32 Moreover, Moreover, other studies have demonstrated that the organic addition compound of lithium halide and alcohol has excellent ionic conductivity. 33,34 Meanwhile, lithium iodide can be dissolved in water or various alcohols and solidified back to a crystal after solvent drying at an elevated temperature. ...
A mixed ionic (Li1.3Al0.3Ti1.7(PO4)3: LATP) and electronic conductor (porous carbon: C) hybrid layer can effectively enhance the electrochemical performance of cathode materials. In this work, a sustainable low-temperature synthesis strategy (≤ 200℃) combining ball milling and solvent-recrystallization of lithium iodide is proposed to prepare the LATP/C coated LiNi1/3Co1/3Mn1/3O2 (LNCMO) material. The characterizations of structures and morphology reveal that LATP and porous carbon powder are mixed into the ethanol dissolved lithium iodide by a simple ball milling process, then the lithium iodide is recrystallized to serve as a binder when ethanol is vaporized at a low temperature to coat uniform thickness and homogeneously distributed LATP/C on the surface of LNCMO cathode. The charge-discharge results illustrate that the cycling performance and rate discharge capability of the active materials coated with LATP/C are significantly superior to the bare LNCMO. AC impedance analysis confirms that lower charge transfer resistance and higher Li+ ion diffusion coefficient are achieved in cathode materials. This work successfully exploited a novel low-temperature cathode coating method based on lithium iodide solvent-recrystallization and obtained results comparable to high-temperature processes without suffering from side reaction problems.
... Furthermore in this category belong all processes that involve immiscible systems where the electrolyte is present in the aqueous phase only, such as carbon capture utilization and/or sequestration (CCUS) [1,2], and oil and gas production from conventional [3] and unconventional [4,5] reservoirs. The participation of mixed-solvent systems or even non-aqueous electrolyte solutions in innovative applications, such as power generation through reverse electrodialysis [6], fuel cell technology [7] and lithium batteries [8], enhances the need for accurate thermodynamic description of such mixtures as well. ...
In this work, the eSAFT-VR Mie equation of state (EoS) is extended to low relative permittivity, non-aqueous solutions. The effect of using different relative permittivity relations for the electrolyte solutions is studied, ranging from experimentally measured values to a salt-composition independent relative permittivity. Furthermore, the effect of using different approaches for the characteristic diameters in the Debye-Hückel and Born terms is presented. The eSAFT-VR Mie EoS is reparametrized using aqueous mean ionic activity coefficients, individual ion activity coefficients and densities with different relations for the relative permittivity. Afterwards, the performance of these models on non-aqueous solutions is evaluated based on the Mean Ionic Activity Coefficients of salts in non-aqueous solutions. The conclusion is that a mole fraction based mixing rule for the relative permittivity yields the best extrapolation from aqueous to non-aqueous solutions, and achieves quantitative predictions for the mean ionic activity coefficients of monovalent salts in methanol and ethanol without additional adjustable parameters.
... Optimisation potentials have been elaborated in previous investigations on REDHE for electricity generation [34][35][36][37][38], and for hydrogen production [24,[39][40][41]. The choice of electrolyte composition, regeneration technology and ion-exchange membrane performance have been identified as particularly important influencing factors [32,39,42]. ...
The reverse electrodialysis heat engine (REDHE) is a promising salinity gradient energy technology, capable of producing hydrogen with an input of waste heat at temperatures below 100 °C. A salinity gradient drives water electrolysis in the reverse electrodialysis (RED) cell, and spent solutions are regenerated using waste heat in a precipitation or evaporation unit. This work presents a non-equilibrium thermodynamics model for the RED cell, and the hydrogen production is investigated for KCl/water solutions. The results show that the evaporation concept requires 40 times less waste heat and produces three times more hydrogen than the precipitation concept. With commercial evaporation technology, a system efficiency of 2% is obtained, with a hydrogen production rate of 0.38 gH2 m−2h−1 and a waste heat requirement of 1.7 kWh gH2−1. The water transference coefficient and the salt diffusion coefficient are identified as membrane properties with a large negative impact on hydrogen production and system efficiency. Each unit of the water transference coefficient in the range tw=[0–10] causes a −7 mV decrease in unit cell electric potential, and a −0.3% decrease in system efficiency. Increasing the membrane salt diffusion coefficient from 10−12 to 10−11 leads to the system efficiency decreasing from 2% to 0.6%.
... For the perfect slip and no-slip conditions, the calculations of De k applied s ¼ 7:4 [ps] for water and s ¼ 50 [ps] for methanol. Conductivity data for the De k calculations was correlated from Chen et al.,[106] Wu et al.,[107] and Bešter-Rogač et al.[108] Andrés González de Castilla, S. Müller and I. SmirnovaJournal of Molecular Liquids 360 (2022) 119398 ...
We present a novel, thermodynamically consistent modification of the Pitzer-Debye-Hückel term and its extension for concentration dependent density, molar mass and relative permittivity. This extension is validated for ionic liquids by comparison with a reference model from the literature and, in contrast to similar extensions, also applied to conventional salts with small spherical ions in aqueous, mixed and non-aqueous solvents. The central novelty is the inclusion of a modified parameter of closest approach, which improves the overall qualitative performance of the Pitzer-Debye-Hückel term over the complete relative permittivity range. Gibbs-Duhem consistency is retained in the modified extension and sample calculations for aqueous [BMIM][BF4] and aqueous NaCl are provided. The novel, modified and extended term with concentration dependent properties is combined with the predictive COSMO-RS-ES model for the calculation of phase equilibria and activity coefficients in electrolytes with conventional salts. The performance of the COSMO-RS-ES model for predictions of salt solubility in fully non-aqueous media improves significantly upon introduction of concentration dependent properties within the long-range electrostatics. Modelling performance with the modified extended Pitzer-Debye-Hückel term outperforms modelling with the unmodified extension as well as with the conventional term with no extension. The correlated relative permittivity of the mixture is overestimated with respect to experimental values and kinetic depolarization effects provide a plausible explanation for this observation. Overall, our results support the consistent introduction of concentration dependent properties within the electrostatic theory in order to improve the modelling of electrolytes with particular emphasis on non-aqueous electrolytes.
... For the evaporation method, the dilute is commonly kept at below 1 mol kg −1 , giving a significant resistance contribution. Wu et al. [134] studied the electrical conductivity of LiCl, LiBr and LiI to assess their feasibility for use in a REDHE with a MED regeneration unit. A methanol-water mixture was proposed as solvent due to favourable electrochemcial and thermodynamic properties. ...
The Reverse electrodialysis heat engine (REDHE) combines a reverse electrodialysis stack for power generation with a thermal regeneration unit to restore the concentration difference of the salt solutions. Current approaches for converting low-temperature waste heat to electricity with REDHE have not yielded conversion efficiencies and profits that would allow for the industrialization of the technology. This review explores the concept of Heat-to-Hydrogen with REDHEs and maps crucial developments toward industrialization. We discuss current advances in membrane development that are vital for the breakthrough of the RED Heat Engine. In addition, the choice of salt is a crucial factor that has not received enough attention in the field. Based on ion properties relevant for both the transport through IEMs and the feasibility for regeneration, we pinpoint the most promising salts for use in REDHE, which we find to be KNO3, LiNO3, LiBr and LiCl. To further validate these results and compare the system performance with different salts, there is a demand for a comprehensive thermodynamic model of the REDHE that considers all its units. Guided by such a model, experimental studies can be designed to utilize the most favorable process conditions (e.g., salt solutions).
... For a LiCl concentration of 14 wt%, specific electricity consumption was between 12% and 20% lower compared to 34 wt% LiCl. This can be attributed to a decrease in electrolytic conductivity in concentrated aqueous LiCl solutions greater than 7 mol·kg −1 [63] (approximately 23 wt%). ...
The objective of this work was to evaluate obtaining LiOH directly from brines with high LiCl concentrations using bipolar membrane electrodialysis by the analysis of Li+ ion transport phenomena. For this purpose, Neosepta BP and Fumasep FBM bipolar membranes were characterized by linear sweep voltammetry, and the Li+ transport number in cation-exchange membranes was determined. In addition, a laboratory-scale reactor was designed, constructed, and tested to develop experimental LiOH production tests. The selected LiCl concentration range, based on productive process concentrations for Salar de Atacama (Chile), was between 14 and 34 wt%. Concentration and current density effects on LiOH production, current efficiency, and specific electricity consumption were evaluated. The highest current efficiency obtained was 0.77 at initial concentrations of LiOH 0.5 wt% and LiCl 14 wt%. On the other hand, a concentrated LiOH solution (between 3.34 wt% and 4.35 wt%, with a solution purity between 96.0% and 95.4%, respectively) was obtained. The results of this work show the feasibility of LiOH production from concentrated brines by means of bipolar membrane electrodialysis, bringing the implementation of this technology closer to LiOH production on a larger scale. Moreover, being an electrochemical process, this could be driven by Solar PV, taking advantage of the high solar radiation conditions in the Atacama Desert in Chile.
