Solutions Of Alkali Metals Research Articles

Phosphorus‐based anodes for fast‐charging alkali metal ion batteries

AbstractAdvancing fast‐charging technology is an important strategy for the development of alkali metal ion batteries (AMIBs). The exploitation of a new generation of anode material system with high‐rate performance, high capacity, and low risk of lithium/sodium/potassium plating is critical to realize fast‐charging capability of AMIBs while maintaining high energy density and safety. Among them, phosphorus‐based anodes including phosphorus anodes and metal phosphide anodes have attracted wide attention, due to their high theoretical capacities, safe reaction voltages, and natural abundance. In this review, we summarize the research progress of different phosphorus‐based anodes for fast‐charging AMIBs, including material properties, mechanisms for storing alkali metal ions, key challenges and solution strategies for achieving fast‐charging capability. Moreover, the future development directions of phosphorus‐based anodes in fast‐charging AMIBs are highlighted.image

Preparation and Characterization of Red Mud-Based Geopolymer Composited with Rice Husk Ash for the Adsorption of Bromocresol Green in Aqueous Solution

Geopolymer-based industrial waste as red mud (RM) was successfully obtained in the presence of different loadings of rice husk ash (RHA). During the preparation, the added amounts of RHA in the geopolymer composition were varied from 10 to 50 % when the mass ratio of binder solution (Na2SiO3) and activated alkali-metal solution (NaOH 7 M) were 2.5 and the curing condition was fixed at 333 K within 24 h. For characterization, the surface morphology was evaluated by scanning electron microscope (SEM) equipped with the energy-dispersive X-ray, which detected the distribution of elements before and after the geopolymerization. To indicate the formation of geopolymer, Fourier–transform infrared spectroscopy (FT-IR) was used. The effect of the loading amounts of RHA on the Brunauer–Emmett Teller (BET) surface area value and Barrett–Joyner–Halenda (BJH) pore size of the obtained geopolymers were determined using a nitrogen gas adsorption instrument. In the bromocresol-green (BG) adsorption performed at pH 2, the higher addition of RHA in the geopolymer composition enhanced the adsorption capacities within 180 minutes. In addition, the adsorption behavior of the mixed geopolymer to BG fits well the Langmuir model, indicating that the adsorption occurs on the homogeneous monolayer surface of geopolymer. From this study, the RHA could be a natural potential filler to improve the BG-uptake of RM-based geopolymer in wastewater treatment.

Effect of Red Mud and Rice Husk Ash-Based Geopolymer Composites on the Adsorption of Methylene Blue Dye in Aqueous Solution for Wastewater Treatment.

In this study, geopolymer originating from locally industrial byproducts as red mud (RM) was successfully prepared in the presence of different loadings of rice husk ash (RHA) used for the adsorption of methylene blue (MB) in wastewater. During geopolymerization, various mixing amounts between RM and RHA were conducted when the weight ratio of binder solution/activated alkali-metal solution (Na2SiO3/ NaOH 7 M) was 2.5 and the curing temperature was set at 60 °C for 24 h. As a result, the surface area value of the prepared geopolymer composited with RHA at 0 and 60% was increased from 19.2 to 29.5 m2/g, while the BJH pore size of the prepared geopolymer was reduced to 6.68 and 5.76 nm, respectively. In the dye removal test, higher additions of RHA in the RM-geopolymer maintained better retention of the MB ion due to the increase in the adsorption binding site. The maximum uptake amount of dyes performed at pH 8 was changed from 6.59 to 10.74 mg/g, while RHA was from 0 to 60% after 180 min of immersion in MB solution. The adsorption isotherms well obeyed the Langmuir model, as the relative coefficient R2 was 0.999. Based on these, the initial agricultural waste as RHA and industrial byproducts as RM were valued as functional materials used for dye treatment in wastewater.

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.

Cyan Fluorescent Carbon Quantum Dots with Amino Derivatives for the Visual Detection of Copper (II) Cations in Sea Water

Amino- and carboxyl-functionalized carbon quantum dots (Amino-CQDs) were synthesized through fast and simple microwave treatment of a citric acid, ethylenediamine and ethylenediaminetetraacetic acid (EDTA) mix. The reproducible and stable optical properties from newly synthesized CQD dispersion with a maximum absorbance spectra at 330 nm and the symmetric emission maximum at 470 nm made the Amino-CQDs a promising fluorescence material for analytical applications. The highly aminated and chelate moieties on the CQDs was appropriate for a copper (Cu2+) cation sensor in the linear range from 1 × 10-4 mg/mL to 10 mg/mL with a limit of detection at 0.00036 mg/mL by static fluorescence quenching effects. Furthermore, Amino-CQDs demonstrated stable fluorescence parameters for assays in diluted alkali metal solution (Na+ and K+) and sea water. Finally, a visual sensor, based on Amino-CQDs, was successfully created for the 0.01-100 mg/mL range to produce a colorimetric effect that can be registered by computer vision software (Open CV Python).

Dissolution kinetics of rare earth metal phosphates in carbonate solutions of alkali metals

Treatment of apatite raw materials is associated with the formation of large-tonnage waste – phosphogypsum. The content of rare earth metals in such waste reaches 1 %, which makes it possible to consider it a technogenic source for obtaining rare earth metals and their compounds. Up to the present moment, there are neither processing plants, nor an efficient process flow to handle phosphogypsum dumps. It is rational to use a way that involves extraction of valuable components and overall reduction of phosphogypsum dumps. Such process flow is available with carbonate conversion of phosphogypsum to alkali metal or ammonium sulfate and calcium carbonate upon the condition of associated extraction of rare earth metal (REM) compounds. Associated extraction of REM compounds becomes possible since they form strong and stable complexes with hard bases according to Pearson, which among other things include carbonate, phosphate and sulfate anions. Formation of lanthanide complexes with inorganic oxygen-containing anions is facilitated by the formation of high-energy Ln-O bonds. The study focuses on the dissolution of lanthanide phosphates in carbonate media. It was established that formation of REM carbonate complexes from their phosphates is a spontaneous endothermic process and that formation of lanthanide carbonates and hydroxides serves as thermodynamic limitation of dissolution. A shift in equilibrium towards the formation of carbonate complexes is achieved by increasing the temperature to 90-100 °C and providing an excess of carbonate. The limiting stage of REM phosphate dissolution in carbonate media is external diffusion. This is indicated by increasing rate of the process with an intensification of stirring, first order of the reaction and the value of activation energy for phosphate dissolution from 27 to 60 kJ/mol. A combination of physical and chemical parameters of the process allowed to develop an engineering solution for associated REM extraction during carbonate conversion of phosphogypsum, which included a 4-5 h conversion of phosphogypsum at temperature of 90-110 °C by an alkali metal or ammonium carbonate solution with a concentration of 2-3 mol/l. As a result, a solution with alkali metal (ammonium) sulfate is obtained, which contains REMs in the form of carbonate complexes and calcium carbonate. The rate of REM extraction into the solution reaches no less than 93 %. Rare earth metals are separated from the mother liquor by precipitation or sorption on anion exchange resins, while the excess of alkali metal or ammonium carbonate is returned to the start of the process.

Some peculiarities of the kinetics of interaction of cationic hydrogels based on copolymers of vinyl esters of monoethanolamine and ethylene glycol with copper ions

Over the past few decades, formation of polymer hydrogels complexes with metal ions, including transition ones, attracts the steady attention of researchers. The relevance of such study is due to the fact that the kinetics of swelling and contraction of hydrogels in various media has been studied in many works, however, this question remains insufficiently studied. Cationic hydrogels based on copolymer of vinyl ethers of monoethanolamine (VEMEA) and ethylene glycol (VEEG) as the study subject in the present work have been used. The kinetics of interaction cationic hydrogels based on copolymer of vinyl ethers of monoethanolamine and ethylene glycol with copper ions in aqueous solutions has been studied. It was shown that swelling behavior such hydrogel in this process is characterized two stages. At the initial stages of the interaction of the gel with the copper salt solution, the interaction in question is determined mainly by the displacement of water from the swollen mesh, due to the difference in osmotic pressures inside and outside the sample. At this stage, the kinetics of the gel contraction is described by the same laws as for polyelectrolyte hydrogel in the alkali metal solution. At the second stage, the network charge density increases due to the formation of a complex, and the degree of the gel swelling begins to increase with time. On the basis of the results obtained, it can be assumed that in systems of this kind, metastable states with differences in character from truly equilibrium states, persisting for a long time, can be formed.

Microporosity Enhancement in a One‐Dimensional Imidazolium Caged Metal‐Organic Framework by Highly Selective Postsynthetic Removal of Inner Yttrium Clusters

A one‐dimensional (1D) metal‐organic caged framework (YMOF‐Y) was obtained via self‐assembly of yttrium cations with a U‐shape imidazolium based ligand and the structure was elucidated by single‐crystal X‐ray diffraction analysis. The YMOF‐Y has a unique 1D chain structure composed of octa‐imidazolium based cages. Inside the cage, an inner Y4 cluster connected to yttrium cations of the cage through formate anions is present. The microporosity and flexibility of YMOF‐Y can be improved by an unprecedented postsynthetic removal of the Y4 clusters from the cage by washing with alkali metal solutions. The removal of the Y4 cluster is reflected in a significant change in the properties of the metal‐organic framework (MOF), as confirmed by carbon dioxide sorption measurements and variable temperature powder X‐ray diffraction analysis.

High Adhesion Superhydrophobic Surface Constructed by PDMS-co-PMHS Coatings Embedded with SiO2 Particles

Superhydrophobic surfaces have attracted attention due to their hydrophobic, self-cleaning, anti-icing, and oil/water separation properties. The present study used a nonwoven fabric as a flexible substrate and constructed a high-adhesive superhydrophobic surface by coating the fabric with polydimethylsiloxane (PDMS)-co -polymethyl hydrogen siloxane (PMHS) polymers and embedding mesoporous SiO2 nanoparticles. The water contact angle (WCA) of the superhydrophobic surface was up to 165.2° at a PDMS to PMHS ratio of 4:1. The adhesion to deionized water was 99.7 μN. High hydrophobicity was maintained, even after sandpaper abrasions and flowing water impact. The surface was resistant to acid, alkali, brine, strong oxidation, and heavy metal solutions. The coating exhibited anti-icing and oil/water separation properties. This study provides a facile and effective method for constructing multifunctional superhydrophobic coatings on flexible substrates.

Elucidating the Role of Hydroxide Electrolyte on Anion-Exchange-Membrane Water Electrolyzer Performance

Many solid-state devices, especially those requiring anion conduction, often add a supporting electrolyte to enable efficient operation. The prototypical case is that of anion-exchange-membrane water electrolyzers (AEMWEs), where addition of an alkali metal solution improves performance. However, the specific mechanism of this performance improvement is currently unknown. This work investigates the functionality of the alkali metal solution in AEMWEs using experiments and mathematical models. The results show that additional hydroxide plays a key role not only in ohmic resistance of the membrane and catalyst layer but also in the reaction kinetics. The modeling suggests that the added liquid electrolyte creates an additional electrochemical interface with the electrocatalyst that provides ion-transport pathways and distributes product gas bubbles; the total effective electrochemical active surface area in the cell with 1 M KOH is 5 times higher than that of the cell with DI water. In the cell with 1 M KOH, more than 80% of the reaction current is associate with the liquid electrolyte. These results indicate the importance of high pH of electrolyte and catalyst/electrolyte interface in AEMWEs. The understanding of the functionality of the alkali metal solution presented in this study should help guide the design and optimization of AEMWEs.

The dispersed SiO2 microspheres supported Ru catalyst with enhanced activity for ammonia decomposition

Ru nanoparticles supported on SiO2 microspheres (Ru/SiO2-GUS) were prepared by the glucose-urea-metallic salt method and applied in the decomposition of ammonia. In the glucose-urea-metallic salt method, glucose as the carbon template plays a significant role in the formation of diffusion-beneficial structural properties of Ru/SiO2-GUS, and also induceds the modification of the electronic state of Ru. Ru/SiO2-GUS exhibited higher catalytic activity compared with the catalyst prepared with the impregnation method. The catalytic performance of Ru/SiO2-GUS was further enhanced with the addition of either K or Cs——the addition order and amount strongly affecting the catalytic performance. When the ratio of K/Cs to Ru is 2, the alkali metal (KOH/CsOH) solution is added in the homogeneous solution of glucose, urea, RuCl3 and the colloidal silica, the promotion effect of K/Cs is the strongest, particularly under lower reaction temperatures. However, the promotion effects of K and Cs are different as reveled by the combined results of H2-TPR, XPS and NH3-TPSR. More NH3 can be absorbed on K–Ru/SiO2-GUS and the electron density of Ru decreased. By contrast, more metallic Ru formed on Cs–Ru/SiO2-GUS, facilitating N2 recombination.

Slowing down DNA translocation velocity using a LiCl salt gradient and nanofiber mesh.

Solid-state nanopores are considered an attractive basis for single-molecule DNA sequencing. At present, one obstacle to be overcome is the improvement of their temporal resolution, with the DNA molecules remaining in the sensing volume of the nanopore for a long period of time. Here, we used a composite system of a concentration gradient of LiCl in solution and a nanofiber mesh to slow the DNA perforation speed. Compared to different alkali metal solutions with the same concentration, LiCl can extend the dwell time to 20 ms, five times longer than NaCl and KCl. Moreover, as the concentration gradient increases, the dwell time can be tuned from dozens of milliseconds to more than 100 ms. When we introduce a nanofiber mesh layer on top of the pore in the asymmetric solution, the DNA molecules get retarded by 162-185 [Formula: see text]s/nt, which is three orders of magnitude slower than the bare nanopore. At the same time, because the molecule absorption region becomes larger at the pore vicinity, the higher molecule capture rate improves the detection efficiency.

Experimental research on explosion suppression affected by ultrafine water mist containing different additives.

The suppression effects of pure ultrafine water mist and 5% mass fraction alkali metal (NaCl, Na2CO3, KHCO3, KCl and K2CO3) solutions ultrafine water mist on methane explosion were conducted under five mist concentrations in a sealed visual vessel. Mist diameters of different additive solutions were measured by a phase doppler particle analyzer. Pressure data and dynamic flame pictures were recorded respectively by a high-frequency pressure sensor and a high-speed camera. Results indicate that alkali metal compound can enhance the suppression effect of ultrafine water mist and it was related to the additive type. The suppression order of alkali metal compound for methane explosion was K2CO3>KCl > KHCO3>Na2CO3>NaCl. Meanwhile, additive radicals can obviously affect explosion intensity and it mainly reflected in the reduction of explosion pressure under different mist conditions (K+>Na+, Cl- >HCO3-). The pressure generated from combustion wave accelerating propagation underwent two accelerating rises and was affected by additive type and mist amount. The effect of additive type on explosion intensity (maximum explosion overpressure (ΔPmax), two peak values of pressure rising rate) was similar with flame propagation velocity and were decreased evidently with increasing mist concentration. The enhancement in explosion suppression was due to the combination of improved physical and chemical effects.

Layered Double Hydroxides with the Composition Mn/Al-SO4-A (A = Li, Na, K; Mn:Al ca. 1:1) as Cation Exchangers

Hydrated Mn/Al-SO4-A (A = Li, Na or K) layered double hydroxides with M2+:M3+ molar ratio close to 1:1 were synthesized by co-precipitation with increasing pH. All phases presented solvated alkali metals and sulfate as intercalated species. In the exchange reactions, when sulfate solutions of alkali metals were used, sodium could be partially replaced by potassium, and the same was true for the potassium phase, where potassium could be partially replaced by Na and Li, without removing the intercalated sulfate anions. This class of compounds, considered to be anion exchanger, can also exchange cations, which opens new perspectives for applications.

Thiocyanates as attractive redox-active electrolytes for high-energy and environmentally-friendly electrochemical capacitors.

This manuscript reports on the novel insight into the development of high voltage carbon/carbon electrochemical capacitors operating in aqueous solutions of alkali metals and ammonium thiocyanates (KSCN, NaSCN, LiSCN, and NH4SCN). The effect of salt concentration, electrode porosity and current collectors on the capacitance value, system stability, and power performance has been investigated. Therefore, thiocyanate-based electrolytes were recognized as cheap and highly conductive electrolytic solutions (up to 401 mS cm-1 for NH4SCN at RT) allowing a cell voltage of 1.6 V in a symmetric carbon/carbon system to be achieved. At the same time, they display an attractive redox activity, enhancing the energy of the device with a good performance during cycling.

Selective removal of sodium from alkali-metal solutions with tetraoctylammonium monensin

Accumulation of sodium ions in fresh water limits its use for drinking water. In the greenhouse industry reuse of irrigation water, which still contains valuable nutrients is limited due to an increasing sodium concentration, and next to this high concentrations of sodium also result in corrosion problems. Existing technologies are not yet able to selectively remove sodium to solve above mentioned problems. Therefore, it was tried to develop a novel sodium selective ionic liquid based on the monensin anion combined with the tetraoctylammonium cation. Ionic crystals were obtained instead of an ionic liquid. Nevertheless, it was proven that these crystals could selectively remove sodium. Metal extraction experiments of an aqueous solution containing Li, Na, K, Mg and Ca with the monensin ionic crystals dissolved in toluene showed a selective single stage extraction efficiency of 41wt% for sodium, while the extraction of the other salts was negligible. Regeneration is possible by applying an acidic solution, however this also prevents its reuse.

Pseudohalide-Based Electrolytes for High-Energy Electrochemical Capacitors

Redox-active electrolytes and additives offer a large selection of available species serving for supercapacitor energy enhancement. The first group refers to typical organic compounds like hydroquinone with isomeric forms. There are also several reports on methylene blue and indigo carmine compounds tested on multi-walled carbon nanotubes. Nevertheless, these organic admixtures have limited solubility in water, and/or their bulkiness restricts adsorption at the interface. Apart from organic molecules, another group of electroactive species includes halide ions. Initially, the iodide/iodine and bromine/bromide redox couples were introduced to supercapacitors. To the best of our knowledge, this is the first report on the employment of alkali metal and ammonium thiocyanates (SCN-) aqueous solutions serving as an electrolyte for supercapacitors. The investigation presents a comprehensive study including the effect of salt concentration, the impact of counter anion type (K+, Na+, Li+ and NH4 +), the influence of applied current collectors as well as the effectiveness of asymmetric configuration. Our research proves that symmetric AC/AC system can easily operate up to 1.6 V with high capacitance and great cyclability. The thiocyanate redox shuttle with formal redox potential at +0.77 V vs. SHE preserves the positive electrode against oxidation and contrarily to iodides or bromides, oxidized SCN- specimen (e.g. polythiocyanogen) in a polymeric form does not evaporate from the system (unlike I2 or Br2). A comparative study on the effect of salt concentration and dependence on the type of current collectors (gold, titanium, and stainless steel) was performed using the KSCN aqueous solutions at various concentrations (1-7 mol∙L-1). It has been demonstrated that the highest concentration of SCN- specimen (7 mol∙L-1) preserved the best performance whatever the current collector used. However, on Ti and stainless steel current collectors, the activity of SCN- seems to be slightly reduced and more ‘capacitive’ profile has been observed. More in-depth studies demonstrated that the system based on 7 mol∙L-1 KSCN aqueous solution preserved high capacitance values even at 10 A∙g-1 current load and retained high energy density (~30 Wh∙kg-1) up to 10 kW∙kg-1 of power rate. Furthermore, we observed that kind of current collector strongly influences the cycle life of the system. Although the gold current collectors provided the highest capacitance during first 1000 cycles, their cyclability is limited to 2 000 cycles. For stainless steel-based systems, the capacitance retention reached 10 000 cycles at 1.6V voltage range.

Phenomenological study of viscosity and density of alkali metal hydroxide solutions

Alkaline solutions are widely used in many industries. For dilute solutions, physicochemical properties, such as solubility of gases, hydration numbers and mobility of ions are well known. A relatively new trend is using concentrated alkaline solutions to obtain ferrates. In these processes, the solution concentration of more than 8 M is used. Studying the processes of transport of matter and charge in concentrated alkaline solutions requires updating the data on the hydration numbers and radii of ions, the effect of concentration, viscosity and nature of electrolytes on them. A method for determining the hydration numbers of alkali metal cations in hydroxide solutions, based on calculating the number of water moles per mole of cations at concentrations close to the limit was proposed. In addition, the influence of ions, strengthening and breaking the solution structure on the density and viscosity of alkali metal solutions was examined. It was shown that primary hydration of ions has the predominant impact on the solution viscosity in dilute solutions, and secondary - in concentrated. It was found that a sharp increase in the solution viscosity with increasing concentration occurs with decreasing distance between ions up to 3,7×10 -7 m. At high concentrations, the solution density is higher in hydrated cations with smaller dimensions. High density of lithium hydroxide solutions in concentrations of from 2 to 4 M can be explained by the fact that the positively hydrated cation is embedded in the structure of water without a significant increase in its volume.

The alkali metals: 200 years of surprises

Alkali metal compounds have been known since antiquity. In 1807, Sir Humphry Davy surprised everyone by electrolytically preparing (and naming) potassium and sodium metals. In 1808, he noted their interaction with ammonia, which, 100 years later, was attributed to solvated electrons. After 1960, pulse radiolysis of nearly any solvent produced solvated electrons, which became one of the most studied species in chemistry. In 1968, alkali metal solutions in amines and ethers were shown to contain alkali metal anions in addition to solvated electrons. The advent of crown ethers and cryptands as complexants for alkali cations greatly enhanced alkali metal solubilities. This permitted us to prepare a crystalline salt of Na(-) in 1974, followed by 30 other alkalides with Na(-), K(-), Rb(-) and Cs(-) anions. This firmly established the -1 oxidation state of alkali metals. The synthesis of alkalides led to the crystallization of electrides, with trapped electrons as the anions. Electrides have a variety of electronic and magnetic properties, depending on the geometries and connectivities of the trapping sites. In 2009, the final surprise was the experimental demonstration that alkali metals under high pressure lose their metallic character as the electrons are localized in voids between the alkali cations to become high-pressure electrides!

Diastereoselective desymmetrization of diarylphosphinous acid-borane amides under Birch reduction.

Treatment of diarylphosphinous acid-borane amides possessing chiral amido functionality with an alkali metal solution in liquid ammonia induced a preferential dearomatization of one aryl substituent at phosphorus leading to the formation of non-equimolar amounts of diastereomers. Diastereoselectivity of dearomatization depends strongly on the structure of a chiral auxiliary.