Aqueous Salt Research Articles

2D Germanane‐MXene Heterostructures for Cations Intercalation in Energy Storage Applications

AbstractHeterostructures offer an exceptional possibility of combining individual 2D materials into a new material having altered properties compared to the parent materials. Germanane (GeH) is a 2D material with many favorable properties for energy storage and catalysis, however, its performance is hindered by its low electrical conductivity. To address the low electrochemical performance of GeH, a heterostructure of GeH and Ti3C2Tx is fabricated. The Ti3C2TX is a layered material belonging to the family of MXenes. The resulting heterostructure (GeMXene) at a defined mass ratio of GeH and Ti3C2Tx shows superior capacitive performance that surpasses that of both pristine materials. The effect of the size of cations and anions for intercalation into GeMXene in different aqueous salt solutions is studied. GeMXene allows only cation intercalation, which is evidenced by the gravimetric electrochemical quartz crystal microbalance (EQCM) technique. The capacitive performance of the GeMXene is compared in neutral, acidic, and alkaline electrolytes to determine the best electrochemical performance. This unleashes the potential use of GeMXene heterostructure in different electrolytes for supercapacitors and batteries. This work will pave the way to explore the heterostructures of other 2D materials such as novel MXenes and functionalized germanane for highly energy‐storage efficient systems, and beyond.

Removal of volatile methyl siloxanes in an anoxic two-phase partitioning bioreactor operated with hydrophobic biomass

Volatile methyl siloxanes (VMS) generated during the anaerobic digestion of organic matter laden with polydimethylsiloxane are key biogas pollutants responsible of irreversible damage to energy-production equipment. This study presents a next-generation two-phase partitioning bioreactor operated with hydrophobic biomass under anoxic conditions for the removal of octamethylcyclotetrasiloxane (D4) and decamethylcyclopentasiloxane (D5) as model VMS commonly found in biogas. When supplied in mixture, D4 and D5 average removal efficiencies (RE) of 26.7 ± 6.4 and 24.1 ± 5.9 % were achieved in the control operating phase using only aqueous mineral salt medium. Addition of 15 % (v/v) of silicone oil boosted the reactor performance, resulting in RE of up to 69.4 ± 9.7 and 85.1 ± 1.6 % for D4 and D5, respectively. D5 removal was enhanced when no D4 was fed, reaching a D5 RE of 91.8 ± 4.0 % and revealing a competitive inhibition between both VMS. The VMS removal in presence of silicone oil was concomitant with nitrate consumption rates of 412 ± 267–1846 ± 1605 mg m−3h−1. Microbial attachment on the water/silicone oil interface was confirmed by observations in the microscope at a 100 × magnification as well as by changes in the silicone oil color and texture. 16S rRNA high-throughput sequencing showed that while Mycobacterium was by far the predominant genera attached to silicone oil with a relative abundance of 92.2 %, Mycobacterium, Romboutsia, Clostridium, Intestinibacter, and Terrisporobacter were the predominant bacterial genera in aqueous phase after 127 days of operation with relative abundances of 25.3, 25.2, 12.3, 7.7, and 5.9 %, respectively.

Inorganic Nanoparticles Embedded in Polydimethylsiloxane Nanodroplets.

To stabilize and transport them through complex systems, nanoparticles are often encapsulated in polymeric nanocarriers, which are tailored to specific environments. For example, a hydrophilic polymer capsule maintains the circulation and stability of nanoparticles in aqueous environments. A more highly designed nanocarrier might have a hydrophobic core and a hydrophilic shell to allow the transport of hydrophobic nanoparticles and pharmaceuticals through physiological media. Polydimethylsiloxane, PDMS, is a hydrophobic material in a liquid-like state at room temperature. The preparation of stable, aqueous dispersions of PDMS droplets in water is problematic due to the intense mismatch in surface energies between PDMS and water. The present work describes the encapsulation of hydrophobic metal and metal oxide nanoparticles within PDMS nanodroplets using flash nanoprecipitation. The PDMS is terminated by amino groups, and the nanodroplet is capped with a layer of poly(styrenesulfonate), forming a glassy outer shell. The hydrophobic nanoparticles nucleate PDMS droplet formation, decreasing the droplet size. The resulting nanocomposite nanodroplets are stable in aqueous salt solutions without the use of surfactants. The hierarchical structuring, elucidated with small-angle X-ray scattering, offers a new platform for the isolation and transport of hydrophobic molecules and nanoparticles through aqueous systems.

Corrosion-driven droplet wetting on iron nanolayers

The classical Evans’ drop describes a drop of aqueous salt solution, placed on a bulk metal surface where it displays a corrosion pit that grows over time producing further oxide deposits from the metal dissolution. We focus here on the corrosion-induced droplet spreading using iron nanolayers whose semi-transparency allowed us to monitor both iron corrosion propagation and electrolyte droplet behavior by simple optical means. We thus observed that pits grow under the droplet and merge into a corrosion front. This front reached the triple contact line and drove a non radial spreading, until it propagated outside the immobile droplet. Such chemically-active wetting is only observed in the presence of a conductive substrate that provides strong adhesion of the iron nanofilm to the substrate. By revisiting the classic Evan’s drop experiment on thick iron film, a weaker corrosion-driven droplet spreading is also identified. These results require further investigations, but they clearly open up new perspectives on substrate wetting by corrosion-like electrochemical reactions at the nanometer scale.

Thermal properties of multi-layered seamed fabrics under wet state

PurposeIn experiments utilising sweat solution and distilled water, seamed ensembles performed less thermally efficiently than unseamed fabrics.Design/methodology/approachWater may not accurately reflect perspiration when testing multi-layered clothes for thermal comfort in wet state. Most researchers used water or sodium chloride (NaCl) to measure wet state thermal comfort. However, human perspiration is an extremely complex mixture of aqueous chemicals, including minerals, salts, lipids, urea and lactic acid. This study compares the effects of simulated sweat solution to distilled water on the thermal behaviour of a multi-layered fabric assembly with different seam patterns.FindingsExperiment results show that stitching decreases thermal resistance and thermal conductivity. Seam pattern of 10 cm diagonal spacing is more thermally resistant than 2.5 cm diagonal spacing. In comparison to that of simulated sweat, fabric that has been moistened with distilled water exhibits increased thermal conductivity. Hollow polyester wadding or micro polyester wadding as the intermediate layer exhibits greater thermal resistance than multi-layered construction with spacer fabric as middle layer.Originality/valueThis study considers human perspiration while designing protective clothing for wet thermal comfort.

Understanding the Anomalous Diffusion of Water in Aqueous Electrolytes Using Machine Learned Potentials.

The diffusivity of water in aqueous cesium iodide solutions is larger than that in neat liquid water and vice versa for sodium chloride solutions. Such peculiar ion-specific behavior, called anomalous diffusion, is not reproduced in typical force field based molecular dynamics (MD) simulations due to inadequate treatment of ion-water interactions. Herein, this hurdle is tackled by using machine learned atomic potentials (MLPs) trained on data from density functional theory calculations. MLP based atomistic MD simulations of aqueous salt solutions reproduce experimentally determined thermodynamic, structural, dynamical, and transport properties, including their varied trends in water diffusivities across salt concentration. This enables an examination of their intermolecular structure to unravel the microscopic underpinnings of the differences in their transport properties. While both ions in CsI solutions contribute to the faster diffusion of water molecules, the competition between the heavy retardation by Na ions and the slight acceleration by Cl ions in NaCl solutions reduces their water diffusivity.

Clouding of TX-100 and promethazine hydrochloride mixture: Impacts of Na salts on the physicochemical parameters and interaction forces linked with studied components

Interest in the phase separation behaviors and interactions between non-ionic surfactants and various drug species in aqueous salt solutions have grown significantly in recent years due to their extensive applications in industry and medicine. This study explored the clouding characteristics of a triton X-100 (TX-100) and promethazine hydrochloride (PMH) mixture in various aqueous sodium salt (such as NaOAc, NaOxal, Na2CO3, NaHCO3, and NaNO3) solutions. The physicochemical variables and interaction forces between TX-100 and PMH species in different sodium salt media were successfully determined by measuring the cloud point (CP). Different electrolyte solutions have been found to alter the clouding behavior of TX-100 + PMH. The CP magnitudes for TX-100 + PMH combinations decreased as the Na salt concentrations were increased, and the respective CPs decreased in the order: Na2CO3 > NaOxal > NaHCO3 > NaOAc > NaNO3. The salting-out effect played a significant role in decreased CP, possibly due to the reduction in water solubility of solutes in the presence of other soluble ions within the mixtures. The ΔGc0 of TX-100 and the employed drug mixture in aqueous salt media was positive, demonstrating the non-spontaneous nature of the clouding process. However, the non-spontaneity of phase separation in the corresponding mixtures decreased as the electrolyte content of the solution increased. The ΔHc0 and ΔSc0 were negative, suggesting that the clouding progression in the studied mixtures was exothermic and driven by enthalpy change. The evaluation of the intrinsic enthalpy gain (ΔHco,∗) and the compensation temperature (Tc) provided evidence of the interactions between TX-100 and PMH species. This research is significant and may be useful in different industries, including for formulating various drugs in the pharmaceutical industry.

Film Coatings Based on Aqueous Shellac Ammonium Salt"Swanlac®ASL 10"and Inulin for Colon Targeting.

Over the past decades, increasing interests took place in the realm of drug delivery systems. Beyond treating intestinal diseases such as inflammatory bowel disease, colon targeting can provide possible applications for oral administration of proteins as well as vaccines due to the lower enzymatic activity in the distal part of GIT. To date, many strategies are employed to reach the colon. This article encompasses different biomaterials tested as film coatings and highlights appropriate formulations for colonic drug delivery. A comparison of different films was made to display the most interesting drug release profiles. These films contained ethylcellulose, as a thermoplastic polymer, blended with an aqueous shellac ammonium salt solution. Different blend ratios were selected as well for thin films as for coated mini-tablets, mainly varying as follows: (80:20); (75:25); (60:40). The impact of blend ratio and coating level was examined as well as the addition of natural polysaccharide "inulin" to target the colon. In vitro drug release was measured in 0.1M HCl for 2h followed by phosphate buffer saline pH 6.8 to simulate gastric and intestinal fluids, respectively. Coated mini-tablets were exposed to fresh fecal samples of humans in order to simulate roughly colonic content. Several formulations were able to fully protect theophylline as a model drug up to 8h in the upper GIT, but allowing for prolonged release kinetics in the colon. These very interesting colonic release profiles were related to the amount of the natural polysaccharide added into the system.

Development of a spray dryer’s mathematical model for control tasks

The sustainable development paradigm includes the most efficient material and energy resources using in production processes. One of the ways to achieve this goal is creating the effective automated control systems. At the same time, such systems effective functioning is impossible without adequate mathematical models for control objects. Thus, the actual task of this study is to create the control object – a spray dryer -model-, which could be used in the control system.
 It was established that one of the main devices in the sodium tripolyphosphate production is a spray dryer in which the aqueous salts suspension is dried by flue gases. The obtained powdery product which is fed into the calcination furnace. The work investigated convective drying, where the material is in direct contact with the drying agent – furnace gas. To drying process control by the drying agent temperature.
 The existing works analysis showed that the mathematical model developing process of a spray dryer requires in-depth research into the physical nature of processes which taking object's operation’s various factors into account. The object presentation can be carried out with different approaches taking into account various important production factors, but at the same time it should be as close as possible to the nature of process. The development of the spray drying process model is carried out for regulation the moisture at the finished product.
 The beginning of the research is the structural and parametric diagram creation of a spray dryer taking into account all input and output values which allow to determine the control disturbance channels. A material balance based on the moisture and loose matter amount and a gas environment heat balance is compiled. The transfer functions component calculation is carried out using the Kramer method. 
 The presented results of the research make it possible to build and analyse the spray dryer mathematical model taking into account the requirements for the substance moisture content be dried and the control process analysis by the drying agent temperature changing. The transient characteristics of the spray dryer by the disturbance and control channels, which are calculated and presented in the research make it possible to compare the control object behaviour with and without taking heat loss into the environment the assumptions into account.

Review of the current state of technology for capacitive deionization of aqueous salt solutions

The availability of clean water at affordable prices is one of the key technological, social, and economic challenges of the 21st century. The increased extraction of groundwater worldwide is leading to the gradual intrusion of salty water into sources and water horizons. In order to use this water for industrial and agricultural purposes, or as drinking water, it needs to be purified and desalinated. Thus, methods of desalinating water of different salinity levels, ranging from brackish to seawater, are becoming more prominent. The overall goal of current research is to make water desalination technologies more energyefficient and cost-effective. One promising technology that meets these requirements is capacitive deionization (CDI) of water. This technology has been widely known for over 30 years, but significant progress in CDI research has only been achieved in recent years. In this review, we examine the currently developed architectures of CDI cells, advancements in carbon materials, and discuss the prospects and challenges of commercializing this technology.

Unveiling the formation mechanism of polydisperse iron oxide nanoparticles in coprecipitation route

Coprecipitation is the simplest, fastest, and most inexpensive method for preparing metal oxide nanoparticles (NPs). It is considered one of the most convenient methods for simultaneously precipitating two or more aqueous metal salt precursors (such as chlorides, nitrates, oxychloride, etc.) into NPs in a basic solvent, yielding uniform composition. However, the main drawback of this route is the production of NPs with a broad size distribution (polydispersed particle formation), which limits their use in various applications. The present work addresses the experiments and formation mechanism of polydispersed iron oxide magnetite (Fe3O4) NPs using this route. Experiments involving the drop-wise addition of mixed ferric (Fe3+) and ferrous (Fe2+) chloride salt solutions to NaOH base solution at room temperature resulted in a polydispersed Fe3O4 NP system containing both large and small particles at the end of 30 min of the reaction. A mechanism is proposed to explain the formation of these polydispersed Fe3O4 NPs based on the time scales of different individual particle formation events and the experimental aging time. The mechanism elucidates that the time scales of events such as Fe3O4 nucleation, diffusional-limited and Ostwald ripening growth of small and large particles, and the coagulation of two small particles or a small particle with a large particle are smaller, and completed within the experimentally allowed aging time. Conversely, the coagulation time for two large particles exceeds the experimental time, preventing complete coagulation. As a result, incomplete coagulation of large particles and the completion of all other events lead to the formation of a polydispersed Fe3O4 NP system at the end of the synthesis. The combined experiments and time scale-based mechanism explain the polydispersed NP formation in the coprecipitation route, and the insights gained from this understanding can be beneficial for optimizing synthesis conditions to achieve a controlled size distribution of Fe3O4 and other NP systems.

Preparation of graphene oxide composited zinc oxide films by electrostatic spray deposition for humidity sensors

This work aimed to study the preparation of graphene oxide (GO) and zinc oxide (ZnO) composited films by electrostatic spray deposition for use in fabricated humidity sensors. The physical properties of prepared films were examined with X-ray diffraction, Raman spectroscopy, and scanning electron microscope. Subsequently, a humidity sensor was fabricated using a low-cost interdigitated electrode pattern with the print circuit board. The humidity sensing behaviors were assessed with fixed humidity levels in a saturated aqueous salt solution in the humidity range of 11 – 93%RH. The impedance value of the device was obtained with a precision LCR meter. It was found that the composited film of 0.50 %wt. GO demonstrated the highest humidity response with optimized humidity sensitivity, hysteresis error, and response/recovery times of 2.68 ´ 103, 4.89%, and 228/19 s, respectively. Moreover, the equivalent circuits for the prepared device at various humidity levels were acquired with impedance spectroscopy to propose the mechanism for the humidity sensing of the device.

Mechanism to form nanosized oxides when burning aqueous carbohydrate salt solutions

This paper describes a method for the synthesis of nanosized oxide powders exemplified by Al2O3, MgO, and SiO2, which includes combustion of a saturated aqueous solution of salts and carbohydrates with multi-stage thermal treatment. A new approach to the synthesis of dispersed oxides with controlled properties has been developed. Particular attention is paid to the selection of optimal synthesis parameters (ratio of components, temperature, processing time) and analysis of phase transformations in the process of formation of nanosized powders with low bulk density. The stages of structural transformations of nanosized oxide particles during multistage heat treatment of an element-containing polymer matrix have been established. The synthesized Al2O3, MgO, and SiO2 nanoparticles are highly reactive due to their disordered defect structure.

Electrohydrodynamic Redox Printing: A Swiss Army Knife of Metals Microfabrication?

The dissolution and deposition of metals in solvents is widely known and used in a large range of applications, from electroplating to electro-machining. More recently, it has also been used for additive manufacturing (AM) at the sub-micron scale, since electroplated metals offer as-deposited high-quality metals (in terms of porosity and contamination) compared to other small scale AM techniques [1,2]. These intricate, high-quality metal structures have a range of applications in microelectromechanical systems, photonics or micro-robotics. However, the nature of the deposition process requires a conductive substrate to provide the electrons necessary for the localized reduction of metal ions. This requirement renders the direct fabrication of microelectronic devices using electrochemical small scale AM a challenge, as often deposition on electrically insulating substrates is required.Here, we present our work on electrohydrodynamic redox printing (EHD-RP), an electrochemical small scale AM technique, and our efforts towards deposition on various substrates. We’ll first introduce EHD-RP with a focus on our recent work on the deposition from aqueous metal salt solutions onto conductive substrates. We’ll then discuss strategies to expand the concept of EHD-RP towards deposition on non-conductive substrates and how electrically floating structures can be fabricated. These strategies render EHD-RP a versatile technique for metals microfabrication.[1] M. Nydegger, A. Pruška, H. Galinski, R. Zenobi, A. Reiser and R. Spolenak. Additive Manufacturing of Zn with Submicron Resolution and its Conversion into Zn/ZnO core-shell structures. Nanoscale, 2022[2] L. Hirt, A. Reiser, R. Spolenak and T. Zambelli. Additive Manufacturing of Metal Structures at the Micrometer Scale. Adv. Mater., 29(17), 2017

Solubility modeling of hydrogen sulfide in aqueous sodium salt solutions

Accurate solubility prediction of hydrogen sulfide in aqueous electrolyte solutions is critical for gas exploitation and geological storage. However, there is a lack of electrolyte Equation of State model that can accurately calculate the solubilities of hydrogen sulfide in aqueous electrolyte solutions over wide ranges of temperature, pressure, and salt molality. This work presents a modeling study on the solubilities of hydrogen sulfide in pure water and several aqueous sodium salt solutions. The thermodynamic framework used in this work is an electrolyte version of Cubic-Plus-Association Equation of State. The model’s temperature-dependent ion-gas binary interaction parameters are obtained by regressing the experimental solubilities in the aqueous electrolyte solutions. The modeling results show that the electrolyte Cubic-Plus-Association Equation of State can satisfactorily correlate the solubilities of hydrogen sulfide in aqueous electrolyte solutions over wide ranges of temperature, pressure, and salt molality. For the typical water–sodium chloride–hydrogen sulfide system, the model can satisfactorily correlate the gas solubilities with the mean relative deviation being 6.2%, with the temperature up to 593.95 K, pressure up to 32.30 MPa, and salt molality up to 6.0 mol⋅kg−1 water. Moreover, the salting-out effects and model adaptability are analyzed and discussed.

Impact of hierarchical water dipole orderings on the dynamics of aqueous salt solutions

Ions exhibit highly ion-specific complex behaviours when solvated in water, which remains a mystery despite the fundamental importance of ion solvation in nature, science, and technology. Here we explain these ion-specific properties by the ion-induced hierarchical dipolar, translational, and bond-orientational orderings of ion hydration shell under the competition between ion-water electrostatic interactions and inter-water hydrogen bonding. We first characterise this competition by a new length λHB(q), explaining the ion-specific effects on solution dynamics. Then, by continuously tuning ion size and charge, we find that the bond-orientational order of the ion hydration shell highly develops for specific ion size and charge combinations. This ordering drastically stabilises the hydration shell; its degree changes the water residence time around ions by 11 orders of magnitude for main-group ions. These findings are fundamental to ionic processes in aqueous solutions, providing a physical principle for electrolyte design and application.

Salt effects on the reactivity for ligand substitution reactions of [Ru(CN)5OH2]3− anion with two naphthalene substituted ligands (nitroso‐R‐salt and α‐nitroso‐β‐naphthol) in presence of Tetrapropylammonium bromide (Pr4NBr) and Sodium chloride (NaCl)

AbstractThe kinetics of the ligand exchange reaction between aquapentacyanoruthenate(II) [Ru(CN)5OH2]3− ion and naphthalene substituted ligands [α‐nitroso‐β‐naphthol (αNβN), and nitroso‐R‐salt (NRS)] has been studied in aqueous salt solutions of sodium chloride (NaCl) or tetrapropylammonium bromide (Pr4NBr) salt. The kinetics was monitored spectrophotometrically at 525 nm corresponding to the λmax of reddish‐brown‐colored substituted products, [Ru(CN)5(αNβN)]3− or [Ru(CN)5(NRS)]3−. Increasing the ionic strength of the reaction mixture using NaCl, exerted a negative salt effect on the rate of formation of naphthalene‐substituted products. At the same time, an increment in the concentration of Pr4NBr imparted a positive salt effect on the reaction. The observed rate constant (kobs) exhibits linear increment with respect to the concentration of NRS or αNβN while remaining invariant with variation in [Ru(CN)5OH2]3−. The computed activation parameters for NRS (∆H# = 24.55 kJ mol−1, Ea = 27.03 kJ mol−1, ∆G# = 87.83 kJ mol−1, and ∆S# = – 212.5 J K−1 mol−1) and αNβN ((∆H# = 17.33 kJ mol−1, Ea = 19.81 kJ mol−1, ∆G# = 87.87 kJ mol−1, and ∆S# = – 236.7 J K−1 mol−1) also support the proposed mechanism.

A Heteronuclear NMR Study of Aqueous Lithium Salt Solutions of l-Alanine: Revealing Solute Hydrophobic Association through the NMR B' Coefficient.

In the present study, a set of heteronuclear NMR approaches has been adopted to investigate the solution behavior of a small hydrophobic solute l-alanine in the presence of lithium (Li) salts. The presence of salts plays a major role in determining the structure and solvation of biomolecules. It therefore evokes interest to understand the effect of Li salts on amino acids (alanine), the building block of biomolecules. The ionic solute dynamics in the present case has been probed using 1H, 7Li, and 13C nuclei available in the aqueous Li salt solution of l-alanine. Nuclear longitudinal spin relaxation of alanine protons was examined at a variable concentration range of three lithium salts, i.e., LiCl, Li2SO4 and LiClO4, to introduce the NMR B' coefficient for each salt defining ionic solute/solvent interaction in the solution. Analysis of the active relaxation mechanism of 7Li spin-lattice relaxation further revealed the presence of alanine in the solvation shell of Li ion depending on the anionic counterpart.

Interactions between γ-alumina surfaces in water and aqueous salt solutions

Particle agglomeration is relevant to numerous industrial applications and consumer products. The present work explores interactions between and agglomeration of gamma (γ)-alumina nanoparticles in pure water and dilute aqueous salt solutions. To characterize surface- and salt-specific effects, potential of mean force (PMF) profiles between γ-alumina surfaces ([110] and [100] facets) are extracted using classical molecular dynamics (MD) simulations. Supporting experiments are conducted using dynamic light scattering (DLS) to investigate agglomeration at the macroscale. The ion pairs considered are sodium chloride, ammonium acetate, barium nitrate, and barium acetate; sampling a broad range of the Hofmeister series. As particle surfaces approach contact, free-energy fluctuations of the PMF profiles reflect structural adjustments of the intervening aqueous phase. We extract values for the cohesive energy from the MD results, and parse the resultant effective pair interactions into van der Waals and electrostatic contributions. Molecular scale findings from simulations correlate with hydrodynamic radii of γ-alumina nanoparticles, obtained from DLS experiments. The results highlight the applicability of molecular simulations to identify the origins of macroscale observables.

Aqueous Potassium Salt of L-Cysteine as Potential CO2 Removal Solvent: An Investigation on Physicochemical Properties and CO2 Loading Capacity

The operational and economic constraints suffered by amine solvents for CO2 removal have motivated the research on an alternative solvent with better performance and cost-effectiveness. Amino acid salt (AAS) has been identified as an interesting green solvent, an alternative to commercial amine solvents. The present work evaluated the physicochemical and CO2-solubility properties of potassium L-cysteine (K-CYS), a naturally occurring amino-acid-based solvent for CO2 removal from natural gas. Its physicochemical properties, including density, viscosity, and refractive index, were measured at different temperatures ranging between 298.15 and 333.15 K and a concentration range of 5 to 30 wt.%. Based on the experiment, all properties were found to decrease with increasing temperature and increase with increasing concentration. The experiments also demonstrated a significant reduction of CO2 loading from 2.4190 to 1.1802 mol of CO2/mol of K-CYS with increasing solvent concentration from 10 to 30 wt% at 313.15 K and 20 bar (g).