Aqueous Lithium Chloride Solutions Research Articles

Concentration effects on aqueous lithium chloride solutions. Molecular dynamics simulations and x-ray scattering studies

Molecular dynamics simulations have been performed on aqueous LiCl solutions over a wide range of salt concentrations, using a flexible SPC/E water model. The resulting molecular dynamics structure factors agree remarkably with recently published x-ray ones. The diffusion coefficients of both ions and water decrease with increasing salt concentration. The self-diffusion coefficients of lithium and chloride are nearly equal at higher salt concentration, showing that large clusters of ions move as an entity. The deduced reorientational correlation time for the dipole moment speeds up as the salt concentration increases, indicating the presence of an angular jump model. The dielectric constant decreases with increasing salt concentration.

Reentrant condensation of lysozyme: Implications for studying dynamics of lysozyme in aqueous solutions of lithium chloride.

Recent studies have outlined the use of eutectic solutions of lithium chloride in water to study microscopic dynamics of lysozyme in an aqueous solvent that is remarkably similar to pure water in many respects, yet allows experiments over a wide temperature range without solvent crystallization. The eutectic point in a (H2O)R(LiCl) system corresponds to R ≈ 7.3, and it is of interest to investigate whether less-concentrated aqueous solutions of LiCl could be used in low-temperature studies of a solvated protein. We have investigated a range of concentrations of lysozyme and LiCl in aqueous solutions to identify systems that do not show phase separation and avoid solvent crystallization on cooling down. Compared to the lysozyme concentration in solution, the concentration of LiCl in the aqueous solvent plays the major role in determining systems suitable for low-temperature studies. We have observed interesting and rich phase behavior reminiscent of reentrant condensation of proteins.

Modeling and Global Sensitivity Analysis of a Solar Powered Air Cooling System Using Liquid Desiccant

Solar energy technology is an option for energy saving in building air conditioning. A theoretical investigation of an open cycle solar air cooling system using aqueous Lithium Chloride solution as liquid desiccant is presented in this paper. The purpose of this work is to analyze the influences of both internal loads and external forcing, on the studied system by developing a computational code related to its mathematical model. The simulation results justify the choice of the system design. Indeed, it was highlighted that the higher is the outdoor temperature; the better is the coefficient of performance (COP) of the system. Furthermore, a global sensitivity analysis of the system model, achieved using Fourier Amplitude Sensitivity Test method, allowed us to identify the most influential factors that were ranked in a decreasing order of their influence degree on the system COP. Hence, key factors to be controlled for improving the system overall performance are specified.

Combined heat and mass transfer analysis during the dehumidification process within a plate type heat exchanger

Liquid desiccant systems have been paid attention because of its advantages in energy saving and an environmental friendliness. The use of liquid desiccant systems offers design and performance advantages over the solid desiccant systems, especially when solar energy is used for regeneration. The objective of this paper is to analyze the simultaneous heat and mass transfer characteristics of lithium chloride aqueous solution for the plate type dehumidification system. The effects of process air and solution inlet conditions on the dehumidification performance are studied in this study. It is found that the heat transfer coefficient of the air side gives much more significant effect on the absorption rate and dehumidification effectiveness than those of the solution and the coolant sides while the mass transfer coefficient of the solution side gives more significant effect than that of the air side. It is also found that the solution concentration is the most important factor for absorption performance improvement during the dehumidification process.

Concentration-Dependent Self-Diffusion of Water in Aqueous Solutions of Lithium Chloride Confined to Porous Glasses

1H pulsed field gradient nuclear magnetic resonance has been used to study the concentration dependent self-diffusion of water in aqueous solutions of lithium chloride in bulk solutions and in these solutions confined to porous glasses with pore sizes of 6 and 100 nm. For the analysis of the experimental results, an analytical description, which is accounting for the water dynamics around and within the ion’s hydration shell, is applied. In the 100 nm pores, the overall water self-diffusion coefficient is reduced by a tortuosity factor and no influence on the dynamics within the hydration shell is detected, while in the 6 nm pores, a significant increase of the mobility of the hydrating water molecules is observed.

Characterization of a 6Li-loaded liquid organic scintillator for fast neutron spectrometry and thermal neutron detection

The characterization of a liquid scintillator incorporating an aqueous solution of enriched lithium chloride to produce a scintillator with 0.40% 6Li is presented, including the performance of the scintillator in terms of its optical properties and neutron response. The scintillator was incorporated into a fast neutron spectrometer, and the light output spectra from 2.5MeV, 14.1MeV, and 252Cf neutrons were measured using capture-gated coincidence techniques. The spectrometer was operated without coincidence to perform thermal neutron measurements. Possible improvements in spectrometer performance are discussed.

Sudden switchover between the polyamorphic phase separation and the glass-to-liquid transition in glassy LiCl aqueous solutions

Lithium chloride aqueous solutions (LiClaq solutions) below 10 mol.% are vitrified by cooling from room temperature to 77 K at 0.3 GPa. We examine the solvent state of the glassy sample and its transformation by heating at 1 atm using low-temperature differential scanning calorimetry and Raman spectroscopy. This experimental study suggests strongly that the solvent state of the glassy LiClaq solution closely relates to the state of high-density amorphous ice. Moreover, we reconfirm that the separation into the low-density amorphous ice and the glassy highly concentrated LiClaq solution occurs in the glassy dilute LiClaq solution at ∼130 K, not the glass-to-liquid transition which is commonly observed in the glassy LiClaq solution above ∼10 mol.%. In order to interpret the sudden switchover between the glass-to-liquid transition and the phase separation at ∼10 mol.%, we propose a state diagram of LiClaq solution which connects with a polyamorphic state diagram of pure water and discuss a possibility that the electric field induces a polyamorphic transition of water.

Slow dynamics of water molecules in an aqueous solution of lithium chloride probed by neutron spin-echo

Aqueous solutions of lithium chloride are uniquely similar to pure water in the parameters such as glass transition temperature, Tg, yet they could be supercooled without freezing down to below 200 K even in the bulk state. This provides advantageous opportunity to study low-temperature dynamics of water molecules in water-like environment in the bulk rather than nano-confined state. Using high-resolution neutron spin-echo data, we argue that the critical temperature, Tc, which is also common between lithium chloride aqueous solutions and pure water, is associated with the split of a secondary relaxation from the main structural relaxation on cooling down. Our results do not allow distinguishing between a well-defined separate secondary relaxation process and the "excess wing" scenario, in which the temperature dependence of the secondary relaxation follows the main relaxation. Importantly, however, in either of these scenarios the secondary relaxation is associated with density-density fluctuations, measurable in a neutron scattering experiment. Neutron scattering could be the only experimental technique with the capability of providing information on the spatial characteristics of the secondary relaxation through the dependence of the signal on the scattering momentum transfer. We propose a simple method for such analysis.

Hydration structure in concentrated aqueous lithium chloride solutions: A reverse Monte Carlo based combination of molecular dynamics simulations and diffraction data

We report on a comparison of three interaction potential models of water (SPC/E, TIP4P-2005, and SWM4-DP) for describing the structure of concentrated aqueous lithium chloride solutions. Classical molecular dynamics simulations have been carried out and total scattering structure factors, calculated from the particle configurations, were compared with experimental diffraction data. Later, reverse Monte Carlo structural modelling was applied for refining molecular dynamics results, so that particle configurations consistent with neutron and X-ray diffraction data could be prepared that, at the same time, were as close as possible to the final stage of the molecular dynamics simulations. Partial radial distribution functions, first neighbors, and angular correlations were analysed further from the best fitting particle configurations. It was found that none of the water potential models describe the structure perfectly; overall, the SWM4-DP model seems to be the most promising. At the highest concentrations the SPC/E model appears to provide the best approximation of the water structure, whereas the TIP4P-2005 model proved to be the most successful for estimating the lithium-oxygen partial radial distribution function at each concentration.

Adsorption behaviors of trivalent actinides and lanthanides on pyridine resin in lithium chloride aqueous solution

The adsorption behaviors of trivalent actinides and lanthanides on pyridine resin in lithium chloride aqueous solution were investigated. The adsorbed amounts of lanthanides and the degree of mutual separation of lanthanides increased with an increase in the concentration of lithium chloride in aqueous solution. The group separation of the trivalent actinides and lanthanides was observed. This separation phenomenon is similar in a hydrochloric acid solution. However, the adsorption behavior of lanthanides in lithium chloride is different from their behavior in a hydrochloric acid solution. This fact shows that the adsorption mechanisms of lanthanides in a lithium chloride aqueous solution and in a hydrochloric acid solution are different; the adsorption mechanisms are attributed to the ion exchange in a hydrochloric acid solution, and to the complex formation with pyridine group in a lithium chloride solution.

Water dynamics in a lithium chloride aqueous solution probed by Brillouin neutron andx-ray scattering

We studied the collective excitations in an aqueous solution of lithium chlorideover the temperature range of 270–205 K using neutron and x-ray Brillouinscattering. Both neutron and x-ray experiments revealed the presence of low- andhigh-frequency excitations, similar to the low- and high-frequency excitations in purewater. These two excitations were detectable through the entire temperature rangeof the experiment, at all probed values of the scattering momentum transfer (0.2 Å − 1 < Q < 1.8 Å − 1). A wider temperature range was investigated using elastic intensity neutron and x-rayscans. Clear evidence of the crossover in the dynamics of the water molecules inthe solution was observed in the single-particle relaxational dynamics on theµeV (nanosecond) time scale, but not in the collective dynamics on the meV (picosecond) timescale.

Combination of air-source heat pumps with liquid desiccant dehumidification of air

This paper proposes a frost-free air source heat pump system with integrated liquid desiccant dehumidification, in which frosting can be retarded by dehumidifying air before entering an outdoor heat exchanger. And the water removed from the air is used to humidify a room. Simulation is carried out at a dry-bulb temperature of −7 to 5.5°C and a relative humidity of 80% depending on the frosting conditions. The results show that the coefficient of performance (COP) is in the range of 2.6–2.9, which is 30–40% higher than that of heat pump heating integrated with an electric heater humidifying system. And it is found that the optimum value of the concentration of lithium chloride aqueous solution is 37% for the frost-free operation mode. Experiments are conducted for liquid desiccant system under low air temperature and high relative humidity conditions. Experimental results show that the dew point of the dehumidified air is decreased by 8°C and the humidity ratio of the humidified air is kept at 8.1gkg−1, which ensures the frost-free operation of the heat pump evaporator and the comfortable level of room humidity simultaneously. The heating load of solution is 3–4.5 times larger than cooling load of solution, which agrees with the assumption given at the part of the simulation. Furthermore, the deviations between the calculated COPLHRU and the experimental results are within 33%.

Cyclic Voltammetry of Ion Transfer for Phenylpropanolamine Hydrochloride at Water|Nitrobenzene Interface

AbstractThe transfer on phenylpropanolamine ion, PPAH+, has been studied at the Interface between Two Immiscible Solutions (ITIES). The polarizable potential range was determined by cyclic voltammetry at the interface between an aqueous solution of lithium chloride (LiCl) and a nitrobenzene (NB) solution of electrolyte tetrabutylammonium tetraphenylborate (TBATPB). The half‐wave potential of ion transfer for phenylpropanolamine accross the water|NB interface was found 465.3 mV. The peak separation, the diffusion coefficient, and the standard ion transfer potential of PPAH+ were observed to be 59.1 mV, 1.7 × 10−6 cm2/s, and 104.6 mV, respectively. The temperature of experiment was kept constantly at 25 ± 1 °C using water flow thermostate.

Electrochemical Lithiation of Silicon Clathrate-II

The clathrate-II compound NaxSi136 (x → 0) was synthesized as a precursor for electrochemical lithiation via sodium extraction from the Zintl-Phase NaSi. The final composition was determined to be Na1.3Si136 via a Rietveld refinement. Electrochemical lithiation of this clathrate-II compound yielded a potential plateau at 300 mV whose capacity is in good agreement with 24 lithium atoms being inserted in the clathrate-II structure. In order to prove this assumption, several clathrate-containing electrodes were prepared and electrochemically lithiated. Afterwards the electrode material was investigated using 7Li magic-angle spinning (MAS)-NMR spectroscopy. Two signals in a 2:1 ratio at extremely high chemical shifts of 412 and 433 ppm, respectively, relative to 1M aqueous lithium chloride solution, were detected and give the indisputable evidence that lithiation of the clathrate-II framework was successful. Hence, this work presents a new method for filling clathrate cages and moreover, the first lithium containing clathrate compound.

Neutron and X-ray diffraction measurements on highly concentrated aqueous LiCl solutions

New neutron and X-ray diffraction experiments have been performed on concentrated aqueous lithium chloride (LiCl) solutions under ambient conditions, as a function of the salt concentration. The concentration range covers a wide region, between ion-pair:water ratios of about 1:3 (which is about the solubility limit) and 1:15 (which is still rather high a concentration value). Data have been interpreted by means of the Reverse Monte Carlo structural modelling method. It has been established that meaningful ion–water and water–water partial radial distribution functions may be derived even from such limited amount of diffraction data, provided that the diffraction measurements and the method of interpreting them are chosen sensibly. The new data and their analyses suggest the presence of Li + cations with only 3 (or less) coordinated water molecules around them. At the highest concentration, one counter-ion has been found to penetrate into the first hydration sphere of the ions.

EFFECT OF SURFACE MODIFICATION ON STRUCTURAL, OPTICAL AND AMMONIA SENSING PROPERTIES OF INDIUM OXIDE FILMS

Indium oxide (In2O3) films have been prepared by thermal oxidation of pre-deposited indium films onto glass substrate kept at room temperature (35°C). These films were dipped into an aqueous solution (0.1 M) of lithium chloride (LiCl) and aluminum chloride (AlCl3) followed by being fired at 500°C. Based on X-ray diffraction results, it has been observed that pure and Li modified In2O3 films are polycrystalline in nature while Al modified In2O3 film has a prominent peak corresponding to 222 plane of In2O3 . Field emission scanning electron microscopy of pure film shows smaller grains which get transformed to bigger ones for Li modified In2O3 film. In case of Al modified In2O3 film agglomerated small grains are observed. This film also reveals the response of 60% for 100 ppm of ammonia vapors at room temperature. The transparency increased from 23–36% to 53–67% in visible region with Li modification of pure In2O3 film.

The features of structurization of the dilute aqueous solution of lithium chloride at the near-critical and supercritical conditions

Method of integral equations in the RISM approximation was used for the study of the structural properties of the dilute aqueous solution of lithium chloride in the near-critical and supercritical state. The following general trends of structural changes in the solution at its transition from the standard conditions to the supercritical conditions were revealed: destruction of the solvent tetrahedral lattice, thermal dehydration of the cation and anion, and an increase in the contact association. We found that the effect of temperature on the decrease in the fraction of the hydrogen-bonded solvent molecules and the value of the thermal dehydration of the ions is comparable with the influence of the density on the same characteristics. The process of ion association is affected predominantly by temperature, the effect is maximal in the subcritical region.

Polarized Raman spectroscopic study on the solvent state of glassy LiCl aqueous solutions and the state of relaxed high-density amorphous ices

We measure polarized OH-stretching Raman spectra of the glassy lithium chloride aqueous solutions (LiClaq solutions) and the relaxed high-density amorphous ices (HDA). The totally OH symmetric vibrational mode around 3100 cm(-1) (g(1) mode) for the glassy LiClaq solutions of 14.3 mol% and the g(1) mode for the glassy LiClaq solution of 10.0 mol% seem to be similar to the g(1) mode for HDA at high pressure and the g(1) mode for HDA at 1 atm, respectively. This indicates that the solvent state of glassy LiClaq solution relates to the state of HDA and that the attenuation of the salt effect on water is equivalent to the attenuation of the pressure effect on water. This suggests a possibility that the hydration in electrolyte aqueous solution may relate to high-density liquid water.

Temperature and density effects on structural features of a dilute aqueous lithium chloride solution at near- and supercritical conditions

The structural features of a 0.24 molal LiCl(aq) solution at near- ( T = 573 K, ρ 1 = 1.0 g/cm 3, ρ 2 = 0.65 g/cm 3) and supercritical ( T = 1073 K, ρ = 0.65 g/cm 3) conditions were studied by the extended RISM integral equation method. It was found that on transition from ambient conditions into the supercritical state the tetrahedral network of water is destroyed, ions are thermally dehydrated and ion association to contact ion pairs is promoted. The effects of temperature or/and fluid density on the structural changes are analyzed. It was established that rising temperature and decreasing density have a similar effect with regard to the decrease of the average number of H-bonds per water molecule and to thermal dehydration of the ions. On the other hand, ion association is mainly affected by rising temperature and this effect is largest in the subcritical region. However, the largest impact on the structural changes in LiCl(aq) solution comes from the combined influence of T and ρ.

Hybrid liquid desiccant air-conditioning system: Experiments and simulations

This study focuses on a hybrid liquid desiccant air-conditioning system consisting of a conventional liquid desiccant system and a vapour compression heat pump. The hybrid liquid desiccant air-conditioning system is expected to enhance the system efficiency of a conventional liquid desiccant system. In this study, the liquid desiccant is aqueous solution of lithium chloride and the refrigerant of the vapour compression heat pump is R407C. The main feature of this system is that the absorber and regenerator are integrated with the evaporator and condenser respectively. The performance evaluation test is conducted to obtain the primary data. Additionally, the improvement method for the system efficiency is discussed by the mathematical calculations. As a result, the system can dehumidify 5.9 g/kg(DA) under the conditions of summer in Tokyo, Japan. Then, the calculation results show that COPs can become higher by improving the compressor isentropic efficiency and the temperature efficiency of solution heat exchanger.