Aqueous Solutions Of KCl Research Articles

Dual-Metal Sites Drive Tandem Electrocatalytic CO2 to C2+ Products.

The electrochemical conversion of CO2 into valuable chemicals is a promising route for renowable energy storage and the mitigation of greenhouse gas emission, and production of multicarbon (C2+) products is highly desired. Here, we report a 1.4 %Pd-Cu@CuPz2 comprising of dispersive CuOx and PdO dual nanoclusters embedded in the MOF CuPz2 (Pz=Pyrazole), which achieves a high C2+ Faradaic efficiency (FEC2+) of 81.9 % and C2+ alcohol FE of 47.5 % with remarkable stability when using 0.1 M KCl aqueous solution as electrolyte in a typical H-cell. Particularly, the FE of alcohol is obviously improved on 1.4 %Pd-Cu@CuPz2 compared to Cu@CuPz2. Theoretical calculations have revealed that the enhanced interfacial electron transfer facilitates the adsorption of *CO intermediate and *CO-*CO dimerization on the Cu-Pd dual sites bridged by Cu nodes of CuPz2. Additionally, the oxophilicity of Pd can stabilize the key intermediate *CH2CHO and promote subsequent proton-coupled electron transfer more efficiently, confirming that the formation pathway is skew towards *C2H5OH. Consequently, the Cu-Pd dual sites play a synergistic tandem role in cooperatively improving the selectivity of alcohol and accelerating reductive conversion of CO2 to C2+.

Microfluidic Laser-Induced Nucleation of Iron (II,III) Oxide Nanoparticle-Doped Supersaturated Aqueous KCl Solutions.

A capillary-based microfluidic system designed for nonphotochemical laser-induced nucleation (NPLIN) studies coupled with real-time microscopy was used to study NPLIN of iron (II,III) oxide doped aqueous KCl solutions. Supersaturation was achieved by lowering the solution temperature using thermoelectric cooling, and heating was used for the dissolution of crystals downstream to prevent clogging during the flow. The effect of nanoparticle concentration, supersaturation, laser intensity, and filtration was studied. We report laser-induced nucleation using laser intensities as low as 1 MW/cm2 with nanoparticle number densities of ∼109 particles per mL of solution at KCl supersaturations from 1.06 to 1.08. The number of crystals increased with increasing laser intensity, supersaturation, and nanoparticle concentration. We discuss our results with respect to the colloidal impurity-heating mechanism hypothesis and propose a semiempirical model based on the nanoparticle heating and bubble formation due to the absorption of laser energy.

EIS Behavior of Polyethylene + Graphite Composite Considered as an Approximation to an Ensemble of Microelectrodes

The electrical percolation of alternating current through two-phase polyethylene/graphite composite electrodes with different contents of graphite microparticles immersed in aqueous KCl solutions has been studied. Above the graphite content of the first percolation threshold, the electrochemical impedance response of this electrode is associated with an equivalent circuit of resistance Ru in series with a constant phase element (CPE). An insulator material + conducting filler model is proposed in which the electroactive surface is considered as the intersection of the percolation cluster through the solid and the cluster associated with the interfacial region. CPE is analyzed assuming a distribution of microcapacitors of the graphite particles in contact with the dielectric solution and inside the dielectric polymeric phase.

Buried interface modification of condensation reflux-processed SnO2 electron transport layers for CsPbBr3 perovskite solar cells

Low temperature solution-processed SnO2 is favorable for electron transport layer (ETL) of flexible perovskite solar cells (PSCs) owing to their process compatibility. Here, we propose a route of condensation reflux-processed SnO2 ETLs for PSCs using SnCl2 source. However, the low temperature SnCl2-derived SnO2 ETLs are inherently associated with a high defect state density as well as a large amount of H+ and Cl- residual on the surface, which will cause open-circuit voltage (VOC) loss of the devices. To tackle this issue, aqueous solutions of KOH, CsOH, and KCl have been employed to regulate the buried interfaces. The effects of different cations (K+ and Cs+) and anions (OH- and Cl-) on the photovoltaic performance of the devices have been comparatively explored. The buried interface with KOH modification showed the best effect, which not only improved the quality and light absorption of CsPbBr3 perovskite layer but also markedly reduced the defect state density at the interface. The optimal device with an architecture of FTO/SnO2/KOH/CsPbBr3/carbon exhibited a champion power conversion efficiency (PCE) of 7.80 %, VOC of 1.46 V, short-circuit current density (JSC) of 7.50 mA/cm2, and fill factor (FF) of 0.71, compared with the pristine counterpart with a PCE of 5.86 %, VOC of 1.40 V, JSC of 6.37 mA/cm2, and FF of 0.66, respectively. The strategy of low temperature-processed SnO2 ETLs by KOH interface modification may also provide an avenue for other-typed flexible PSCs manufacture.

Density and coefficients of Jones–Dole equation for viscosity measurement of l-isoleucine, l-proline, and l-glutamine in aqueous KCl solution at 298.15–323.15 K

The present studies reported the experimental data on thermophysical properties such as density and viscosity of aqueous solutions of different amino acids namely l-isoleucine, l-proline, and l-glutamine in 1.5 mol/L KCl solution at different temperatures ranging from 298.15 to 323.15 K. Hence, the aim of this study is to investigate interactions between amino acids and KCl solution at dilute concentrations. For understanding amino acid and KCl solution interactions, we will investigate ion–ion and ion–solvent interactions. It has been observed that the density and viscosity rise with amino acid concentration and decrease with temperature. Using the Jones–Dole equation, the viscosity A and B coefficients have been determined. The viscosity B-coefficient values for all the three amino acids in aqueous electrolyte system are depicted as positive. The positive values of B-coefficient indicate a strong alignment of the solvent molecules with solute molecules. The amino acid l-glutamine acts as a structure breaker solute. This structure breaking effect of l-glutamine on solvent may be attributed to the domination of hydrophilic nature of amide group. l-isoleucine and l-proline act as structure maker in electrolyte system.

Harvesting Enhanced Blue Energy in Charged Nanochannels Using Semidiluted Polyelectrolyte Solution.

Blue energy generation in nanochannels based on salinity gradients is currently the most promising method in the area of nonconventional energy production. We used a semidiluted pure sodium carboxymethylcellulose (NaCMC)-KCl aqueous solution to study the characteristics of blue energy generation within a charged nanochannel. We solve the corresponding equations for ionic transport using a numerical technique based on the finite element method. Our analysis focused on the electric double layer (EDL) potential field, open circuit current, diffuse potential, electric conductance, maximum generated pore power, and maximum energy conversion efficiency by varying concentrations of the salt in the left-side reservoir and the bulk polyelectrolyte. The results indicate that as the polyelectrolyte concentration increases, the extent of EDL overlap considerably reduces. With an increase in polyelectrolyte concentration, the open circuit current increases, while the diffuse potential reduces. It was observed that both electrical conductance and maximal pore power improve considerably with higher polyelectrolyte concentrations. Interestingly, our modeling framework demonstrates a power density substantially higher (up to 16.31 W/m2) than earlier configurations and surpasses the established commercial limit (5 W/m2). Furthermore, our findings reveal that the reservoir salt concentration significantly affects the rate of decline in the maximum energy conversion efficiency as the polyelectrolyte concentration increases. The research paves the way for the development of high-power-density devices with several practical applications.

Biodiesel photoelectrocatalytic synthesis employing α-Fe2O3 film decorated with Pt nanoparticles as photoanode

In this work, photoelectrochemical route for biodiesel production using an electrochemical cell configured with platinum and α-Fe2O3 modified with Pt nanoparticles as electrodes was investigated. XRD patterns registered for film prepared by modified hydrothermal method revealed a trigonal structure of the hematite (α-Fe2O3) phase. The α-Fe2O3 film surface was decorated by metallic Pt nanoparticles (PtNP) in order to reduce the charge recombination and improve the photocatalytic efficiency. The band gap energy (EBG) of the α-Fe2O3 and PtNP/α-Fe2O3 films was estimated by UV-Vis spectroscopy at approximately 2.1 eV. Electrochemical measurements showed that the oxide is an n-type semiconductor adequate to be used as a photoanode in biodiesel synthesis. Under polarization conditions, the electrochemical cell changed the pH from 7 to 14 when the system was polarized at 5.0 V. In the synthesis of biodiesel by esterification reaction, oleic acid, 300 µL of 0.1 mol L−1 aqueous KCl solution and methanol were used as precursor reagents. The reaction was carried out free of strong base, such as KOH or NaOH, as a supporting electrolyte. In this route, the reduction of the water molecule occurred on the cathode, with the formation of hydroxyl (OH-) species, methoxy, and consequently fatty acid methyl esters (FAMEs). Thermogravimetric analysis (TGA) and Gas chromatography coupled to mass spectrometry (CG-MS) were performed to evaluate the catalysis products. GC-MS analyzes show that the reaction has a yield of about 7 % with the formation of FAMEs, such as methyl 9-octadecenoate, methyl hexadecanoate and methyl hexadecanoate.

Dual‐metal sites drive tandem electrocatalytic CO2 to C2+ products

The electrochemical conversion of CO2 into valuable chemicals is a promising route for renowable energy storage and the mitigation of greenhouse gas emission, and production of multicarbon (C2+) products is highly desired. Here, we report a 1.4%Pd‐Cu@CuPz2 comprising of dispersive CuOx and PdO dual nanoclusters embedded in the MOF CuPz2 (Pz = Pyrazole), which achieves a high C2+ Faradaic efficiency (FEC2+) of 81.9% and C2+ alcohol FE of 47.5% with remarkable stability when using 0.1 M KCl aqueous solution as electrolyte in a typical H‐cell. Particularly, the FE of alcohol is obviously improved on 1.4%Pd‐Cu@CuPz2 compared to Cu@CuPz2. Theoretical calculations have revealed that revealed that the enhanced interfacial electron transfer facilitates the adsorption of *CO intermediate and *CO−*CO dimerization on the Cu‐Pd dual sites bridged by Cu nodes of CuPz2. Additionally, the oxophilicity of Pd can stabilize the key intermediate *CH2CHO and promote subsequent proton‐coupled electron transfer more efficiently, confirming that the formation pathway is skew towards *C2H5OH. Consequently, the Cu‐Pd dual sites play a synergistic tandem role in cooperatively improving the selectivity of alcohol and accelerating reductive conversion of CO2 to C2+.

CO2 solubility in aqueous solution of salts: Experimental study and thermodynamic modelling

AbstractThere are many economic obstacles and complex engineering problems associated with CO2 capture and storage in saline aquifers that need to be addressed. Overcoming such challenges requires precise knowledge on the fluid phase equilibria of CO2‐brine systems. Having accurate CO2 solubility data over a wide range of temperature and pressure can greatly assist in resolving these obstacles by improving the performance and accuracy of the thermodynamic modeling and subsequent CCS engineering success.CO2 solubility in pure water and NaCl solutions has been widely studied in the literature, however, there is a lack of data on CO2 solubility at lower temperatures (below 298 K). Furthermore, limited phase equilibria data are available for CO2 solubility in CaCl2, MgCl2, and KCl solutions at elevated temperatures (i.e., T > 323.15 K).In this work, the phase equilibria of CO2 and brine systems are investigated experimentally and theoretically. In this study, solubilities of CO2 in pure water and various concentrations of NaCl (10, 15, 20, and 22 wt%), KCl (10, 15, and 22 wt%), CaCl2 (7.5, 10, 15.7, and 23.4 wt%), and MgCl2 (6.7, 11, 18, and 29 wt%) aqueous solutions are reported. All CO2 solubilities were measures at 323.15, 373.15, and 423.15 K and over various pressure ranges, while solubilities in 10 and 20 wt% NaCl aqueous solutions were also measured over the temperature range of 263 to 298 K and pressures up to the hydrate dissociation pressure of each system. Equation of state modelling using the PC‐SAFT and the Cubic Plus Association equations of state, is performed in the theoretical part of the study to validate the measured solubility data. © 2024 The Author(s). Greenhouse Gases: Science and Technology published by Society of Chemical Industry and John Wiley & Sons Ltd.

Investigating antimicrobial behavior of thymol/Zn encapsulated hierarchically structured zeolite and thymol release kinetics

A new bioactive material was proposed by encapsulating thymol molecules and Zn2+ cations within the post-modified intracrystalline voids of hierarchical zeolite X crystals. To enhance the accessibility of thymol molecules within zeolite X crystals, commercial zeolite samples underwent post-synthesis treatment involving consecutive aqueous KCl, NH4Cl, and Na2H2EDTA solutions. The gas adsorption method utilized the encapsulation of both Zn2+ cation and thymol molecules into the resulting hierarchical zeolite X framework, which demonstrated improved antimicrobial activity. While sole thymol-encapsulated zeolite X exhibited no antimicrobial activity against S. aureus, Zn2+ encapsulated zeolite X (ZnX), thymol encapsulated post-treated zeolite X (HX-thy), and both Zn2+ and thymol encapsulated post-treated zeolite X (ZnHX-thy) displayed zone of inhibition values of 18.7 mm, 25.0 mm, and 37.5 mm, respectively. Adding Zn2+ and creating a hierarchical pore system in the zeolite X framework altered the release profiles. The Higuchi kinetic release model has the highest R2 value to describe the process of thymol release from X-thy, whereas the Elovich release model has the best fitting profile of thymol release kinetics from ZnX-thy, HX-thy, and ZnHX-thy. Results indicate that thymol and Zn2+ containing hierarchical porous materials could be beneficial tools for obtaining enhanced antibacterial activity and stability with reduced degradation and volatility of thymol with extended protection against microbial attack due to the controlled release. These findings highlight an innovative approach to designing sustainable and green materials, utilizing modified porous networks that encapsulate natural antibacterial compounds with environmentally benign metal ions.

Experimental solubility of FeCO3 in aqueous 3–20 wt% KCl at 25–80 °C

FeCO3 is a mineral, present in both industrial and natural systems. While the solubility of FeCO3 is determining for CO2 storage, and driving for corrosion, it is not well understood. For the development of rigorous modelling, there is a lack of adequate experimental data under relevant conditions to model carbonated systems containing iron.In this work, the solid-liquid equilibrium (SLE) of the ternary system FeCO3-KCl-H2O was measured at atmospheric pressure at temperatures from 25 to 80 °C. The FeCO3 solubility was studied in aqueous KCl solutions from 3 to 20 wt%. 73 new solubility data points for the systems FeCO3–KCl–H2O are presented together with 73 oxidation data points. Results showed that less than 5% of FeCO3 is oxidized in the electrolyte system. The equilibrium concentration of FeCO3 was obtained after 5–10 days with the fastest equilibrium kinetics obtained at the highest temperature, 80 °C. Temperature had a minor impact on the FeCO3 solubility in aqueous KCl solutions. However, the FeCO3 solubility seemed to slightly decrease with temperature. The solubility data was fitted to a first-order rate equation with molality as driving, to obtain kinetic insights. The dissolution rate decreases as a function of KCl concentrations. In some cases, it was 75 % lower than in NaCl. A rate constant of approximately 0.2 1/day was obtained for most experiments. The FeCO3 solubility and kinetic data obtained in this work will allow for a deeper understanding and better prediction of CO2 corrosion and mineralization, suitable for CO2 storage.

MD Simulation and Analysis of the Pair Correlation Functions, Self-Diffusion Coefficients and Orientational Correlation Times in Aqueous KCl Solutions at Different Temperatures and Concentrations

MD Simulation and Analysis of the Pair Correlation Functions, Self-Diffusion Coefficients and Orientational Correlation Times in Aqueous KCl Solutions at Different Temperatures and Concentrations

Porosity generation via spatially uncoupled dissolution precipitation during plagioclase replacement in quartz undersaturated fluids

The replacement of feldspars is commonly characterized by pseudomorphism and reaction-induced pore generation. However, the effects of compositions of feldspars and fluids on porosity generation during alteration are still poorly understood. In this study, we conducted a series of hydrothermal experiments on plagioclase replacement by 2 M KCl or NaCl aqueous solutions at 600 °C and 150 MPa for 1–8 days, using plagioclase with different compositions (anorthite, An96Ab4; labradorite, An66Ab33Or1; albite, An1Ab99) with or without quartz. Albite replacement by K-feldspar was not affected by the presence of quartz, whereas anorthite was unaltered in the quartz-absent fluid. The replacement of labradorite by KCl(aq) showed different results: in the presence of quartz, labradorite was altered by K-feldspar, whereas in the absence of quartz, alteration proceeded significantly with the generation of large pores hosted by secondary anorthite coupled with euhedral K-feldspar overgrowth. Such textural relationship and oxygen isotope-labeled experiments reveal that silica-deficient fluid enhances the uncoupled dissolution reprecipitation process. The Si and Al ions in the reacted aqueous solution diffused outside the labradorite grains and encountered K+-rich solutions to grow K-feldspar. The experiments with polycrystalline rocks composed of amphibole + labradorite using 2 M KCl aqueous solution indicated the replacement of labradorite grains by anorthite and K-feldspar overgrowth, as found in single-crystal experiments. Our results indicate that the silica concentration in the fluids has different influences on the saturation indices of albite, anorthite, and K-feldspars in saline fluids, which significantly affect the replacement textures and porosity generation in crustal rocks.

Structural study of a novel layered aluminophosphate AlPO-NS having 10-&10-rings micropores by 3D-ED, powder XRD, and solid-state NMR analyses

A crystal structure of a novel aluminophosphate AlPO-NS, which has a crystal morphology of stacked hexagonal plate crystallites (30–50 nm in thickness), was determined utilizing a combination of 3D-ED, powder X-ray diffraction, and solid-state NMR experiments. We previously reported that AlPO-NS could be obtained from a synthetic solution for a typical aluminophosphate AlPO4-5 (Al2O3 : P2O3 : triethylamine : H2O = 1.0 : 1.0 : 3.0 : 250) via AlPO4-5 by prolonged hydrothermal reaction time (T. Kodaira et al. Microporous and Mesoporous Materials 162, 32–35 (2012).). The 3D-ED/microED analysis successfully revealed that AlPO-NS consists of two layers in a unit cell of a hexagonal system. A space group and lattice constants were P6322, and a = 0.941565(12) nm, c = 5.22254(8) nm. A 2D 10-&10-rings micropore structure is incorporated in the layered framework consisting of AlO4, AlO6, and PO4 polyhedra. The structure of AlPO-NS was changed into a disordered structure derived from stacking faults by the calcination above 573 K under the atmosphere. This structural change is due to shrinkage of the interlayer space and (partially) bridging adjacent aluminophosphate layers by dehydration-condensation of facing –OH groups. The calcined AlPO-NS showed nitrogen adsorption ability with a nearly type-I adsorption isotherm. A specific surface area (SBET) and micropore volume (Vmicro) were 300 m2 g−1 and 0.11 mL g−1, respectively. As-synthesized AlPO-NS contained H+ ions for charge compensation and exhibited ion exchange abilities for Na+ and K+ ions when immersed in NaCl and KCl aqueous solutions, respectively. From the above, it was found that AlPO-NS and its calcined form have micropores and physicochemical properties similar to zeolites.

Engineered Conductive Proteins for Supercapacitors

Proteins can be used as building blocks of functional materials for electrochemical applications due to their structural properties and the possibility to tailor their ionic and electronic conductive properties.[1] One of the most attractive applications is in the bioelectronics field, for example as energy storage devices such as Electrical Double Layer Capacitors (EDLCs), due to the nontoxicity and biocompatibility of the materials.[2] EDLCs are primarily used for applications where high power is required during a short period of time. They present several advantages, such as fast charge-discharge cycling, high power density, and outstanding long-term stability.[3]Traditionally, the incorporation of biomaterials in EDCLs is limited because they can be denaturalized in contact with organic solvents or salts. In addition, they easily interact with other cell components resulting in parasitic reactions and their complex purification processes hinder their commercialization.[4] These drawbacks can be overcome by introducing engineered proteins, since their amino acid sequences can be tuned resulting in 3D structures with varying degrees of complexity. Based on this approach, engineered proteins with improved conductivity will be introduced as interlayers with good stability and wettability, to ensure that the ions can shuttle freely between the two electrodes.In our case, consensus tetratricopeptide repeat (CTPR) proteins have been chosen [5] and engineered with the aim of increasing the ionic conductivity of the resulting variants. CTPR variants have been mixed with 5% PEG solutions and drop cast to obtain self-standing films. After being cross-linked, the films have been sandwiched in a two electrodes Swagelok-cell configuration between two electrodes made of activated carbon. KCl (3M) aqueous solution has been used as electrolyte for evaluating the electrochemical performance of the devices.The electrochemical characterization of the EDLC devices has been carried out using cyclic voltammetry (CV) and galvanostatic cycling (GC) to study the effect of the of the engineering strategy of the CTPR proteins on the EDLC performances. The CV curves of the devices using thin films of proteins with distinct mutations show quadratic capacitive responses for all the assembled EDLCs, demonstrating both its ability to isolate the two electrodes and to allow the diffusion of ions. The EDLCs capacitances were calculated and analyzed from the GC characteristics at different charge-discharge currents and compared with commercial glass fiber separators confirming their feasibility as safe and environmentally friendly separators. The ionic diffusive behavior of the devices has been also studied by electrochemical impedance spectroscopy (EIS). Finally, the effect of the thickness, porosity, polarity, wettability, and ionic conductivity of the different protein separators has been addressed to explore the role of the engineered proteins in EDLC devices. Acknowledgements This abstract is part of R&D&I project TED2021-131641B-C44, funded by MCIN/AEI/10.13039/501100011033 and by European Union NextGenerationEU/PRTR. This project has received funding from the European Union’s Horizon 2020 FET Open under the grant agreement No: 964593

Thermodynamic characterization of aqueous solutions of NaCl, KCl, MgCl2 and CaCl2: volumetric, acoustic, viscometric and computational analysis

The volumetric and acoustic properties of alkali and alkaline earth metal salts are ubiquitous in numerous biological and non-biological processes and accurate formulation of their thermophysical properties is a fundamental prerequisite for complete exploration of their diverse applications. To meet this purpose, in this investigation, we herewith report the systematic data of densities ρ, speed of sound u and viscosity η of aqueous binary solutions of the prominent alkali and alkaline earth metal salts viz. NaCl, KCl, MgCl2, and CaCl2 at seven different temperatures T = (288.15–318.15 K) and ambient pressure over the wide concentration range of (0.002–1) mol∙kg−1.These experimental data have been further employed to obtain some important thermodynamic parameters, viz, the apparent molar volume of solute Vϕ, limiting apparent molar volume of solute Vϕ0, isentropic compressibility of solution κS, apparent molar isentropic compression of the solute KS,ϕ, limiting apparent molar isentropic compression of solute KS,ϕ0 and apparent molar expansibility Eϕ0. Further, the coefficient of thermal expansion α*, the second-order derivative of limiting apparent molar volume ∂2Vϕ0/∂T2, Jones-Dole equation viscosity A, B, D coefficients, temperature derivative of B coefficient i.e. dB/dT, activation parameters for viscous flow and hydration number nH have also been computed. The results obtained have been used to elucidate different interactions taking place in the aqueous electrolytic solutions. To corroborate the experimental results, quantum chemical calculations were performed using density functional theory (DFT) by Gaussian software package. The calculations included an analysis of molecular orbitals, with particular emphasis on the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO).

Hydration Processes in HCl and Aqueous Salt Solutions

In this work, the number of hydration of ions (K+ and Cl-, K+ and Br-, K+ and I-, H+ and Cl-, Li+ and Cl-, Cs+ and Cl-, Na+ and Cl-) in dilute aqueous solutions of some electrolytes of KCl, KBr, KI, HCl, LiCl, CsCl, and NaCl was studied by the proposed refractometric method. Further, the effect of polyethylene glycol (PEG-6000) on the hydration processes for ions in aqueous solutions of KCl and KBr was studied. It turned out that when the polymer is introduced into the solution, the hydration numbers of ions decrease, which is apparently due to the role of the PEG oxygen atom competing with ions in interaction with water molecules.

Investigation of the Ability to Detect Electrolyte Disorder Using PET with Positron Annihilation Lifetime Spectroscopy.

Various concentrations (8-300 mmol/L) of NaCl, KCl, and NaCl + KCl aqueous solutions were investigated using positron annihilation lifetime spectroscopy (PALS). A strong dependence of the o-Ps intensity as a function of the solution concentration was demonstrated. On this basis, the mean positron lifetime and the sum of counts in a selected time interval were proposed as reliable parameters for detecting disturbances in the ion balance of living organisms. The use of these parameters for differentiating healthy and cancerous tissues allows for the development of auxiliary diagnostic methods in a new generation of PET scanners equipped with a PALS detection module.

Solubility and solvation energetics of L-histidine in aqueous NaCl/KCl electrolyte media

This article describes the solubility etiquette of an important amino acid L-histidine in chloro aqueous solutions of alkali metals (Na, K) under equilibrium saturated conditions through an analytical gravimetric technique at equidistant temperatures. Different thermodynamic parameters along with transfer Gibbs energies under standard conditions were estimated using theoretical methods and experimental solubilities. The way of surrounding by solvent molecules of solute L-histidine in the used media is discussed based on different modes of interactions occurring during solvation. The experimental section describes that the L-histidine solubility enhances in an aqueous KCl solution rather than in NaCl solution. The drop down in L-histidine solubility with moving up electrolyte concentrations at a certain temperature is caused by the salting-out effect. For the studied amino acid, the salting out effect is more pronounced in NaCl electrolyte at any temperature. Amino acid shows higher solubility with rising temperature in both electrolytes’ solutions. The current study suggests that the physical properties of NaCl and KCl and the size of the L-histidine molecules are two crucial factors for the chemical stability of the protein building unit.

Novel High‐Pressure Potassium Chloride Monohydrate and Its Implications for Water‐Rich Planetary Bodies

AbstractSaline water is a common fluid on the Earth‘s surface and in ice planets. Potassium chloride (KCl) is a common salt and is expected to be a ubiquitous solute in salt water in the Universe; however, few studies investigated the behavior of KCl‐H2O system at high pressures and temperatures. In this study, powder and single‐crystal X‐ray diffraction (SC‐XRD), Raman and Brillouin scattering combined with diamond anvil cells were used to investigate the phase relation in the KCl‐H2O system for different KCl concentrations at 0–4 GPa and 298–405 K. The results of powder X‐ray diffraction and Raman scattering demonstrate that a novel KCl hydrate is formed when KCl aqueous solutions transform to solid ice‐VI and ice‐VII at high pressure. Simultaneously, the single‐crystal of KCl hydrate is synthesized from a supersaturated KCl solution at 298 K and 1.8 GPa. The structure is solved by SC‐XRD, indicating a KCl monohydrate with the P21/n space group is formed. We have verified the phase stability of KCl monohydrate by using Raman spectroscopy and density functional theory. Our results indicate that KCl monohydrate is a stable phase under pressure and temperature conditions between 1.6 and 2.4 GPa and 298–359 K. By considering the thermal profile and composition of icy moons, we hypothesize that the formation and decomposition of KCl monohydrate might induce mantle convection in these moons.