Alkaline Earth Metal Salts Research Articles

Self-Assembled Synthesis of Graphene Tubes from Melamine Catalyzed by Calcium Carbonate

This study investigates the carbon products generated by melamine under various heat-treatment temperatures with the catalysis of calcium carbonate. We discovered that the cost-effective precursor melamine readily self-assembles and curls into graphene tubes when catalyzed by the alkaline earth salt CaCO3 at elevated temperatures. Under heat-treatment conditions of 1100 °C and 1200 °C, the growth morphology of graphene tubes with open structures and exceptionally large diameters was observed, and the diameters reached the micron level. These products exhibit a high degree of carbonization and an extremely low nitrogen content, as low as 1.7%. Further, the intensity ratio (ID/IG) of the D band and the G band is as low as 0.79 in Raman characterization. The results show that the products have a certain graphite structure, which proves the catalytic activity of CaCO3. This is attributed to the incorporation of CaCO3 into the raw material system, which impedes the complete thermal decomposition of melamine. On the other hand, the resulting CaO particles are evenly distributed along the tubular products, providing certain support for their self-assembly and growth, thereby achieving the efficient growth of graphene tubes.

Efficient and durable seawater electrolysis with a V2O3-protected catalyst.

The ocean, a vast hydrogen reservoir, holds potential for sustainable energy and water development. Developing high-performance electrocatalysts for hydrogen production under harsh seawater conditions is challenging. Here, we propose incorporating a protective V2O3 layer to modulate the microcatalytic environment and create in situ dual-active sites consisting of low-loaded Pt and Ni3N. This catalyst demonstrates an ultralow overpotential of 80 mV at 500 mA cm-2, a mass activity 30.86 times higher than Pt-C and maintains at least 500 hours in seawater. Moreover, the assembled anion exchange membrane water electrolyzers (AEMWE) demonstrate superior activity and durability even under demanding industrial conditions. In situ localized pH analysis elucidates the microcatalytic environmental regulation mechanism of the V2O3 layer. Its role as a Lewis acid layer enables the sequestration of excess OH- ions, mitigate Cl- corrosion, and alkaline earth salt precipitation. Our catalyst protection strategy by using V2O3 presents a promising and cost-effective approach for large-scale sustainable green hydrogen production.

Optical Basicity for Understanding the Lewis Basicity of Chloride Molten Salt Mixtures.

Currently, there is a lack of reliable measurement techniques for understanding the basicity of molten chloride salts. Optical basicity, an ultraviolet-visible (UV-vis) spectroscopic method for measuring Lewis basicity, is explored for its applicability to molten chloride salts. Shifts in probe ion (Pb2+ and Bi3+) electronic transitions are observed that show that cations in chloride salts follow the same basicity series as in oxide melts, and an increase in basicity is observed with increasing temperature. Pb2+ and Bi3+ are validated as effective probe ions in alkali, alkaline earth, and aluminum-sodium chloride molten salts. However, the utility of Bi3+ is limited by the volatility of BiCl3 at high temperatures, posing a challenge for use in high-temperature molten salt applications. Since optical basicity measures the extent of electron donation, it may be a useful metric for electrochemical corrosion.

Insight into the alkaline earth metal salt promotion for alkali-catalyzed glucose isomerization

An approach to improving the efficiency of alkali-catalyzed glucose isomerization into fructose by adding alkaline earth metal salts was explored. 70.3% fructose yield with 99% fructose selectivity can be achieved in Ca(OH)2–CaCl2 solution at 50 °C for 25 min.

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).

Integrated production of potash fertilizer and formed coke via carbonated consolidation technique

Transforming potassium feldspar (PF) into water-soluble potassium fertilizer traditionally requires high-temperature conditions, a significant challenge in sustainable agriculture. Addressing this, our study innovatively employed the carbonated consolidation process using low-rank semi-coke (SC). By introducing PF and alkaline earth metal salts, we produced high-strength formed coke (FC). Crucially, the combustion heat from FC facilitated the desired transformation in the coke ash. Our findings highlight that FC with PF addition yields a calorific value of 20.8 MJ/Kg, aligning with industrial standards, and significantly curtails emissions of sulfur, nitrogen compounds, and dust, emphasizing its eco-friendly nature. Remarkably, a 96.5% potassium leaching rate was achieved within 4 h at 25 °C. Further analyses showcased the FC's carbonate content's role in drastically reducing the transformation temperature of potassium in PF to a mere 570 °C. This research not only offers a cleaner approach to SC utilization but also paves the way for cost-effective and eco-friendly PF transformations, bearing significant implications for future sustainable agricultural practices.

Characterization of sargassum accumulated on Dominican beaches in 2021: Analysis of heavy, alkaline and alkaline-earth metals, proteins and fats

This paper presents the characterization of sargassum that reached the shores of eight Dominican beaches in 2021. The analysis of heavy, alkaline and alkaline-earth metals was performed by ICP-OES. Twelve heavy metals were studied, with the highest concentrations corresponding to Fe, As, and Zn. Regarding the alkaline and alkaline-earth metals, the highest concentrations were detected for Ca, K, Na and Mg. The high values of arsenic and alkali and alkaline-earth metal salts do not suggest using these algae in agriculture. It is recommended to carry out arsenic speciation studies to assess whether the form in which it is found is bioavailable for plants and animals. The heavy metal contamination index was determined, which ranged between 0.318 and 3.279. Finally, for the first time in the country, the organic fraction of sargassum was analyzed.

Catalytic co-pyrolysis of cellulose over alkali and alkaline earth metal salts for levoglucosan production

A comprehensive study of alkali and alkaline earth metal (AAEM) salts including two different anions (Cl- and CH3COO-) in the catalytic pyrolysis of cellulose to produce levoglucosan (LG), bio-oil, and biochar were investigated. At the same time, the catalytic pyrolysis mechanism was also speculated. The thermogravimetric analyzer (TGA) and lab-scale fixed-bed reactor system were used to determine the thermal degradation process and the pyrolysis products of LG, bio-oil, and biochar. The optimized pyrolysis parameters were obtained by using Box-Behnken design-response surface method. According to the results, AAEM salts significantly boosted the yield of biochar, as well as greatly cut down the output of LG and bio-oil. The rank of effect on LG yield was as follows: CaCl2, MgCl2 > CH3COOK, CH3COONa > (CH3COO)2Mg, (CH3COO)2Ca > KCl, NaCl. Moreover, the addition of AAEM salts considerably dropped the activation energy E of cellulose pyrolysis as well as prompted microcrystalline cellulose pyrolysis under lower temperatures. This study was pivotal in deducing the pathway of cellulose pyrolysis, thereby offering critical insights to hasten the progress of biomass utilization.

Impact of limestone caves and seawater intrusion on coastal aquifer of middle Andaman

Seawater intrusion has become a common problem in coastal and island aquifers with the rise in climate change that greatly affects the majority of developing countries. The island hydrology is very complex and associated with a unique set of environmental characteristics with the dynamic interaction of groundwater, surface water, and seawater. Further, Sea level rise, erratic rainfall, and over-extraction of groundwater triggered salt-water intrusion. A study on seawater intrusion and the effect of limestone caves on groundwater was carried out in middle Andaman using a combination of ionic ratios of major ions. A total of 24 samples and a reference sample from the sea were collected and analysed using ICP, spectrophotometer, and flame photometer. A combination of 10 ionic ratios Cl/HCO3, Ca/(HCO3 + SO4), (Ca + Mg)/Cl, Ca/Mg, Ca/Na, Cl/(SO4 + HCO3), Ca/SO4, K/Cl, Mg/Cl, and SO4/Cl was used to assess the dissolution of limestone minerals and the level of saltwater intrusion into groundwater. The geospatial method was used to extract and combine all the hydrogeochemical parameters and ionic ratios in the GIS platform. Durov plot was used for the interpretation of groundwater chemistry and the identification of natural processes controlling the hydrogeochemistry of the area. The dominance of Ca-HCO3 and Na-HCO3 was confirmed in 48% and 24% of the sample respectively. The equiline graph of chloride with other major ions showed the enrichment of alkali and alkaline earth metal salt in groundwater. Schoeller's diagram depicted the dominance of Cl, Ca, and the sum of CO3 and HCO3 in seawater near Mayabunder. The lower concentration of Na with respect to Cl (64%) and Ca (100%) showed the presence of a reverse ion exchange process. Further, the correlation matrix showed a strong relationship between Cl, K, Ca, and Na. The analysis of X-ray diffraction of the rock samples confirmed the presence of limestones such as Aragonite, Calcite, Chlorite, Chromite, Dolomite, Magnetite, and Pyrite in the study area. The integration of ionic ratios showed moderately affected and slightly affected saline regions in 44% and 54% of the region respectively. Finally, the role of tectonic activities and active lineaments connected to the sea was found to play a major role in the intrusion of seawater where interconnected faults created an opening for surface water to recharge groundwater leading to the deep aquifer.

Conversion of biomass-derived sugars to 1,1,2-trialkoxyethane via a [2 + 4] retro-aldol reaction over alkaline and alkaline earth metal salts of phosphotungstic acid

Catalytic conversion of biomass-derived sugars over alkaline and alkaline earth metal salts of phosphotungstic acid to 1,1,2-trialkoxyethane with high yield.

Splicing oxygen-rich multidentate ligands and characteristic metals to construct flame colorants: abundant structures and attractive colors.

Tetranitroethane (TNE), an energetic compound with high-nitrogen (N%, 26.7%) and oxygen (O%, 60.9%) content, is deprotonated by alkali and alkaline earth metal bases to form the corresponding metal salts of TNE which are characterized by FT-IR spectroscopy, elemental analysis, and single crystal X-ray diffraction. All the prepared energetic metal salts show excellent thermal stabilities, and the decomposition temperatures of EP-3, EP-4, and EP-5 are higher than 250 °C, due to the numerous coordination bonds of the complexes. Furthermore, the energy of formation of the nitrogen-rich salts were calculated utilizing heat of combustion. The detonation performances were calculated with the EXPLO5 software, and the impact and friction sensitivities were determined. EP-7 shows excellent energy performance (P = 30.0 GPa, VD = 8436 m s-1). EP-3, EP-4, EP-5, and EP-8 are more sensitive to mechanical stimulation. These alkali and alkaline earth metal salts of TNE show good monochromaticity by atomic emission spectroscopy (visible light), and may be used as potential flame colorants in pyrotechnics.

OXIDATIVE DIMERIZATION OF METHANE: KINETICS OF THE REACTION

In this article, the textural properties of catalysts and the process of catalytic dimerization of methane using catalysts based on salts of alkali and alkaline-earth metals containing molybdenum and manganese oxides were studied. It was found that the catalytic conversion of methane takes place on the surface of a catalyst that adsorbs oxygen to form an active complex [ZOCH3]. It has been shown that the catalytic conversion of methane can be carried out simultaneously with the formation of ethane and ethylene. At the same time, the percentage of ethylene in the free volume of the reactor increases compared to ethane, which helps the reaction of ethylene formation without oxygen and catalyst. Phenomenological equations for the kinetics of the catalytic reaction of methane dimerization are formulated and rate constants and Arrhenius parameters are calculated.

Theoretical Investigation of the Structure and Physicochemical Properties of Alkaline and Alkaline Earth Metal Perchlorate Solutions in Sulfolane.

To assess the possibility of using solutions of perchlorates of alkali and alkaline earth metals in sulfolane as electrolytes for electrochemical energy storage devices with metal negative electrodes, the physicochemical properties of 0.5 M solutions of Me(ClO4)n (Me = Li, Na, K, Mg, and Ca) in sulfolane were simulated by the method of molecular dynamics. The density, viscosity, conductivity, self-diffusion coefficients, and transport numbers are calculated. Satisfactory agreement between the calculated and experimentally measured properties of 0.5 M solutions of LiClO4 and NaClO4 in sulfolane suggests that the calculated values of the physicochemical properties of solutions of K, Mg, and Ca perchlorates are also close to real values. The study of the structure of solvate complexes of salts of alkali and alkaline earth metals with sulfolane by quantum chemical and molecular dynamics modeling showed that the first solvate shell of metal cations consists of sulfolane molecules. Regardless of the nature of the cation, sulfolane is coordinated to the metal cation by only one oxygen atom. Based on the analysis of the calculated values of the physicochemical properties of solutions of metal perchlorates in sulfolane, it can be concluded that they can be used as electrolyte systems of electrochemical energy storage devices with negative electrodes made of alkali and alkaline earth metals.

Access to Green Pyrotechnic Compositions via Constructing Coordination Polymers: A New Approach to the Application of 3,4-Dinitropyrazole.

Alkali and alkaline-earth metal salts with 3,4-dinitropyrazole (DNP) were synthesized by the reaction of DNP with stoichiometric amounts of the corresponding metal hydroxide-, oxide-, or carbonate-based highly pure salts, and products were fully characterized. Determination of single-crystal structures of all new complexes except for the lithium and strontium salts was performed by X-ray diffraction techniques. The cesium salt crystallized no water among them. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) manifested that these salts have satisfactory thermal stabilities with decomposition temperatures above 210 °C. They also showed that there exists strong bonding of crystallized water among lattices, which disappeared at temperatures equal to or above 115 °C except for salts MES-3, MES-4, and MES-9. In addition, the percentage of water contents was confirmed by using DSC and TGA methods. The constant-volume combustion heats of these metal salts containing DNP anions were measured using an oxygen bomb calorimeter due to their expectant interest in energetic materials, and their standard molar formation enthalpies were obtained. The investigated salts were found to be insensitive toward friction and impact. Findings of burning tests performed with experimental formulations using MES-1, MES-7, MES-8, and MES-9 certify that these four salts might be more promising candidates for application in green pyrotechnics.

Metal salts used as an efficient catalyst to reduce the ring opening polymerization temperature of benzoxazines

An attempt was made to develop low-temperature curing aniline-based benzoxazines (BA-a/BF-a) using various transition metal salts, such as FeCl3, CoCl2, NiBr2, CuCl2, ZnCl2, Zn(OAc)2, CdCl2 and Alkali–Alkaline earth metal salts, such as LiCl, KI and CaCl2 and main group metal salt AlCl3 as an efficient catalyst. The findings of the DSC analysis revealed that the main group and transition metal salts had outstanding catalytic activity and were able to reduce the curing temperature of benzoxazines (BA-a/BF-a). Among the various metal salts, FeCl3, AlCl3, ZnCl2 and Zn(OAc)2 exposed excellent catalytic behavior in lowering the curing temperature of benzoxazines to 145 °C (BA-a) and 150 °C (BF-a) from 217 to 218 °C, respectively. The thermal stability and flame retardant characteristics of the resultant polybenzoxazines (PBz’s), are also studied and included in this work. In the presence of catalysts, the initial degradation temperature almost same, residual char yield increased from 27 to 55%, and the flame retardant properties increased to 39.5 from 28.5 for the resultant PBz’s.

Acid treatment as a beneficiation method for phosphorite waste of Kyzylkum phosphorite plant

This article addresses matters relating to the recycling of waste from the Kyzylkum phosphorite plant in the form of phosphorite slimes, the mass of which exceeds 3 million tons at present. The treatment of slime with sulfuric acid having the concentrations from 2 g/l to 40 g/l made it possible to determine the most optimal concentrations (up to 10 g/l), at which the salts of alkali and alkaline earth metals, uranium and other elements are separated. This method permits obtaining a richer fraction of the useful component, phosphorus(V) oxide (up to 19.1%). At the same time, the pH value of the medium remains in the neutral range. Mass spectroscopy showed that such treatment with sulfuric acid having the concentrations up to 10 g/l allows selectively dissolving carbonates without decomposing phosphates. IR spectra of phosphorite slime after acid treatment do not contain absorption bands characteristic of CO32– groups. In accordance with the obtained results, a low-cost technological scheme for the phosphorite slime utilization was developed, followed by its introduction into the production process without violating the main technological regulations. The enriched slime fraction corresponds in quality to the burdened phosphorite ore and can be used as an additional product.

Dendrite-free alkali metal electrodeposition from contact-ion-pair state induced by mixing alkaline earth cation

Alkali metals are expected to be used for rechargeable metal anode batteries owing to their low electrode potentials and large capacities. However, they face the well-known fatal problem of “dendritic growth” while charging. Here, we present a detailed investigation on electrolytes where alkaline earth salts are introduced to inhibit dendrite growth in alkali metal electrodeposition. Specifically, focusing on CaTFSA 2 as an exemplary additive, we reveal that dendrite-free morphology upon alkali metal electrodeposition can be attained by modifying the solvation structures in dual-cation electrolytes. Addition of Ca 2+ promotes alkali cation (Li + or Na + ) to form the contact ion pairs (CIPs) with the counter anions, which replaces the solvent-separated ion pairs that commonly exist in single-cation electrolytes. The strong binding of the CIPs slows the desolvation kinetics of alkali cations and, consequently, realizes a severely constrained alkali metal electrodeposition in a reaction-limited process that is required for the dendrite-free morphology. • Additive divalent cations lead to flat morphology in Li and Na electrodeposition • Li + /Na + tends to form strong CIPs to alleviate interaction among divalent cations • Increased activation energy of CIPs enables to retain a uniform diffusion field Li et al. report that mixing divalent cations with alkali cations in electrolytes can modify the solvation structure and consequently obtain flat morphology in alkali metal electrodeposition. This finding may represent a step toward active control of reaction kinetics toward metal anode batteries.

Accelerated synthesis of Sn-Beta with less silanols by alkaline (earth) salt for efficient transformation of glucose to methyl lactate

Sn-Beta zeolite is an excellent catalyst for the transformation of biomass derived carbohydrates. However, the long synthesis time restricted its application. Here, alkaline (earth) salt was used as promoter to accelerate the crystallization of Sn-Beta. Different alkaline (earth) salts and the amount of MgCl2 were investigated. The properties of the synthesized samples were characterized by various techniques and compared with Sn-Beta, and the catalytic performance was investigated for the conversion of glucose to methyl lactate (MLA). The results indicate that a small amount of alkaline (earth) salt, especially MgCl2, promoted dramatically the crystallization of Sn-Beta. The full crystallization time was shortened from 15 d to 5 d with the aid of MgCl2 (nMg/nSn of 1.0) for Sn-Beta with nSi/nSn of 100. Sn4+ cations were incorporated into the framework sites, while Mg2+ cations replaced the protons of silanol defects. Mg–Sn-Beta with strong Lewis acid sites and less silanols showed high activity and selectivity for glucose conversion to MLA. The yield of MLA is 20% over the fully crystallized Sn-Beta at 120 °C for 15 h and glucose concentration of 3.1 wt%, which increased significantly to 44% over the fully crystallized 1 Mg–Sn-Beta. Furthermore, Mg–Sn-Beta is stable and recyclable.

The Influence of Accelerated Carbonation on Physical and Mechanical Properties of Hemp-Fibre-Reinforced Alkali-Activated Fly Ash and Fly Ash/Slag Mortars.

The physical and mechanical properties of hemp-fibre-reinforced alkali-activated (AA) mortars under accelerated carbonation were evaluated. Two matrices of different physical and chemical properties, i.e., a low Ca-containing and less dense one with fly ash (FA) and a high Ca-containing and denser one with FA and granulated blast furnace slag (GBFS), were reinforced with fibres (10 mm, 0.5 vol% and 1.0 vol%). Under accelerated carbonation, due to the pore refinement resulting from alkali and alkaline earth salt precipitation, AA hemp fibre mortars markedly (20%) decreased their water absorption. FA-based hemp mortars increased significantly their compressive and flexural strength (40% and 34%, respectively), whereas in the denser FA/GBFS matrix (due to the hindered CO2 penetration, i.e., lower chemical reaction between CO2 and pore solution and gel products), only a slight variation (±10%) occurred. Under accelerated carbonation, embrittlement of the fibre/matrix interface and of the whole composite occurred, accompanied by increased stiffness, decreased deformation capacity and loss of the energy absorption capacity under flexure. FA-based matrices exhibited more pronounced embrittlement than the denser FA/GBFS matrices. A combination of FA/GBFS-based mortar reinforced with 0.5 vol% fibre dosage ensured an optimal fibre/matrix interface and stress transfer, mitigating the embrittlement of the material under accelerated carbonation.

Influence of different salts of alkali and alkaline earth metals on the pyrolysis of Prosopis juliflora

AbstractThis study explores the effect of acetate, oxide and chloride salts of alkali and alkaline earth metals (AAEMs) on the pyrolysis of lignocellulosic biomass. Prosopis juliflora samples were infused using 2% acetate and chloride salts of potassium (CH3COOK, KCl) and the oxide and chloride salts of magnesium (MgO, MgCl2). Dry impregnation technique was employed for the infusion of salts into the biomass matrix. The AAEM salt‐infused biomass was pyrolyzed using a semi‐batch pyrolysis reactor, and the bio‐oils were characterized for variation in chemical composition using gas chromatography–mass spectroscopy. The AAEM salts significantly influenced the pyrolysis process by catalyzing different degradation pathways. Potassium salts catalyzed the ring fission reactions of carbohydrates, resulting in an increase in carboxylic acid yield. On the other hand, magnesium salts promoted the cyclization of the fragmented radicals of the ring fission, resulting in enhanced furan and cycloketone yield. AAEM salts were most effective in catalyzing carbohydrate degradation pathways over the lignin degradation reactions owing to their ability to easily influence polysaccharide C–C bond cleavage over those of lignin aromatic rings. This study also revealed that the anions of AAEM salts also play a major role in biomass pyrolysis. © 2022 Society of Chemical Industry and John Wiley & Sons, Ltd