Alkali Salts Research Articles

Direct Air Capture and Integrated Conversion of Carbon Dioxide into Cyclic Carbonates with Basic Organic Salts.

Direct air capture and integrated conversion is a very attractive strategy to reduce CO2 concentration in the atmosphere. However, the existing capturing processes are technologically challenging due to the costs of the processes and the low concentration of CO2. The efficient valorization of the CO2 captured could help overcome many techno-economic limitations. Here, we present a novel economical methodology for direct air capture and conversion that is able to efficiently convert CO2 from the air into cyclic carbonates. The new approach employs commercially available basic ionic liquids, works without the need for sophisticated and expensive co-catalysts or sorbents and under mild reaction conditions. The CO2 from atmospheric air was efficiently captured by IL solution (0.98 molCO2/molIL) and, subsequently, completely converted into cyclic carbonates using epoxides or halohydrins potentially derived from biomass as substrates. A mechanism of conversion was evaluated, which helped to identify relevant reaction intermediates based on halohydrins, and consequently, a 100% selectivity was obtained using the new methodology.

Unraveling the Mechanism of Alkali Metal Fluoride Post-Treatment of SnO2 for Efficient Planar Perovskite Solar Cells.

The facile synthesis and beneficial properties of tin oxide have driven the development of efficient planar perovskite solar cells (PSCs). To increase the PSC performance, alkali salts are used to treat the SnO2 surface to minimize the defect states. However, the underlying mechanism of alkali cations' role in the PSCs needs further exploration. Herein the effect of alkali fluoride salts (KF, RbF, and CsF) on the properties of SnO2 and PSC performance is investigated. The results show different alkali have significant roles depending on their nature. Larger cations Cs+ preferably locate at the SnO2 film surface to passivate surface defects and enhance conductivity, while smaller cations like Rb+ or K+ cations tend to diffuse into the perovskite layer to reduce trap density of the material. The former effect leads to enhanced fill factor while the latter effect increases the open circuit voltage of the device. It is then demonstrated that a dual cation post-treatment of the SnO2 layer with RbF and CsF achieves PSC with a significantly higher power conversion efficiency (PCE) of 21.66% compared to pristine PSC with a PCE of 19.71%. This highlights the significance of defect engineering of SnO2 using selective multiple alkali treatment to improve PSC performance.

Understanding the Anion Effect of Basic Cobalt Salts for the Electrocatalytic Oxygen Evolution Reaction

Basic cobalt salts with distinct acidic anion Co(OH)x(A)y are efficient electrocatalysts toward the oxygen evolution reaction (OER). However, plenty of present studies are still in the try-and-wrong stage, while the underlying anion effect remains unclear. Herein, a series of Co(OH)x(A)y (A = F–, Cl–, and CO32–) are synthesized via a hydrothermal strategy, and the order of the OER activity is determined to be Co(OH)(CO3)0.5 > Co2(OH)3Cl > Co(OH)F > Co(OH)2. X-ray photoelectron spectroscopy and soft X-ray absorption spectroscopy studies reveal that these Co(OH)x(A)y materials undergo surface oxidation during the OER process, and the highly active Co(IV) content is the dominant factor in deciding the OER performance. Furthermore, quantitative analysis of anion concentrations in the electrolyte solution reveals that the anion leaching ability in Co(OH)x(A)y directly relates to the Co(IV) content and finally the OER catalytic activity, which is the essence of the anion effect and can be summarized as an “anion leaching─metal oxidation” model. Our work not only provides deep understanding of the anion effect of metal basic salt-based OER catalysts but also profound insights for the activation process of the OER pre-catalysts.

Full-Length Transcriptome Analysis of Soybean Cyst Nematode (Heterodera glycines) Reveals an Association of Behaviors in Response to Attractive pH and Salt Solutions with Activation of Transmembrane Receptors, Ion Channels, and Ca2+ Transporters.

Soybean cyst nematode (Heterodera glycines Ichinohe), a devastating pathogen in soybean, was chosen as a model system to investigate nematode behavior and gene expression changes in response to acidic and basic pH and salt signals (pH 4.5, 5.25, 8.6, and 10 and NaCl) through full-length transcriptome sequencing of 18 samples. An average of 4.36 Gbp of clean reads per sample were generated, and 3972 novel genes and 29,529 novel transcripts were identified. Sequence structural variation during or after transcription may be associated with the nematode's behavioral response. The functional analysis of 1817/4962 differentially expressed genes/transcripts showed that signal transduction pathways, including transmembrane receptors, ion channels, and Ca2+ transporters, were activated, but pathways involved in nematode development (e.g., ribosome) and energy production (e.g., oxidative phosphorylation) were inhibited. A corresponding model was established. Our findings suggest that these receptors and ion channels might be potential targets for nematicides or drug discovery.

Role of Accumulated Alkali and Alkaline-Earth Chloride Salts in Hydrochar Formation Produced from Lignocellulosic Biomass

Hydrothermal carbonization (HTC) is an effective method for recovering useful carbon-rich solids from biomass and wet organic waste. This study investigated the effects of the type and amount of alkali and alkaline-earth chloride salts (AAECS) in HTC media on the properties of cornstalk hydrochar by analyzing the yield, elemental composition, surface functionality, and morphology, as well as fuel characteristics. The results suggest that the abundance of AAECS in HTC media may increase the aromaticity and energy recovery of hydrochar by facilitating the dehydration and decarboxylation of biomass. Both anions and cations in AAECS are responsible for these variations, especially for Ca2+, which can selectively affect the dehydration reaction of biomass by promoting the formation of anhydride and inhibiting the reaction between carboxyl and hydroxy to form a lactone. In addition, the high concentration of AAECS in HTC media is beneficial for improving the electron-donating capacity of hydrochar. This work could provide important insights into AAECS’ effects on hydrochar preparation, which arose from the recirculation of HTC aqueous solution.

Improving the Cycling Stability of Aqueous Zinc-Ion Batteries by Preintercalation of Polyaniline in Hydrated Vanadium Oxide.

This paper reports the synthesis and characterization of hydrated vanadium oxide (VOH) and chemically preintercalated polyanilines in VOH, labeled as PAVO-H as the cathode material for aqueous zinc-ion batteries. Synthesized PAVO-H has a high surface area and rod-shaped morphology. PAVO-H has an increased interlayer distance of 13.36 Å. PAVO-H offers high specific capacities of 330 and 225 mAh g-1 at 50 mA g-1 and 4 A g-1 of current densities, respectively, with a 92% capacity retention rate of over 3000 cycles. The preintercalation of polyaniline is likely to catalyze the redox reaction and facilitate and simplify transport kinetics. It is also possible that the preintercalation of polyaniline permits the insertion of large hydrated Zn ions and reduces the formation of zinc basic salts.

Size and Composition Control of Magnetic Nanoparticles

Magnetite nanoparticles are a type of magnetic nanoparticle (MNP) that are inexpensive to make and can be formed in different shapes and sizes. MNPs can be used in DNA/RNA purification, drug delivery, and other biomedical applications. The commonly employed solvothermal route to make these MNPs gives the most uniform products with the smallest size distribution, but there is a need to identify easily controlled changes to reaction parameters that can reliably tune the size and composition of the MNPs made by this method. In this work we report simple and reliable methods whereby adjusting the total water content and basic salt concentration affords size and composition control, respectively. We employ synchrotron X-ray absorption measurements to prove our method offers monotonic control over MNP composition from maghemite-rich (γ-Fe2O3) to the more magnetic magnetite (Fe3O4). This demonstrates a simple, general method to produce particles with high magnetite concentration and the desired size.

High-Contrast Visualization Chemiluminescence Based on AIE-Active and Base-Sensitive Emitters.

Peroxyoxalate chemiluminescence (PO-CL) is one of the most popular cold light sources, yet the drawback of aggregation-caused quenching limits their use. Here, we report a new kind of efficient bifunctional emitter derived from salicylic acid, which not only exhibits typical aggregation-induced emission (AIE) character but also has the ability to catalyze the CL process under basic conditions based on base sensitivity. By taking advantage of these unique features, we successfully confine the CL process on the surface of solid bases and provide a high-contrast visualization of CL emission. This method allows most of the common basic salts like sodium carbonate to be invisible encryption information ink and PO-CL solution to be a decryption tool to visualize the hidden information. The current study opens up an appealing way for the development of multifunction CL emitters for information encryption and decryption applications.

Thermally induced solid-state reaction of Fe2(SO4)3 with NaCl or KCl: a route to β-Fe2O3 synthesis

β-Fe2O3 is a rare crystalline polymorph of the ferric oxide family with an interesting application potential, e.g., in photocatalysis. In this study, the effect of different alkali salts addition, namely NaCl and KCl, on the preparation of β-Fe2O3 via thermally induced solid-state reaction was investigated. Two series of samples were prepared by calcining two different mixtures, Fe2(SO4)3 + NaCl (molar ratio 1:3) and Fe2(SO4)3 + KCl (molar ratio 1:3) at temperatures from 350 to 700 °C. Although the addition of either alkali salt led the preparation of β-Fe2O3 particles in wide temperature range up to 650 °C, differences in the overall phase composition and β-Fe2O3 purity were observed between the two series. The addition of KCl to Fe2(SO4)3 allowed the preparation of pure β-Fe2O3 (≥ 95%) in relatively wide temperature range of 450‒600 °C, while in the case of NaCl, pure β-Fe2O3 (≥ 95%) was found only in samples calcined at 500 °C and 550 °C. Other phases could be identified as additional ferric oxide polymorphs, γ-Fe2O3 and α-Fe2O3. The in situ XRD results suggest that, in the case of NaCl + Fe2(SO4)3 reaction, simultaneous formation of β-Fe2O3 and α-Fe2O3 may be possible between 350 and 500 °C, depending on the reaction conditions.

Design of type-II heterojunction MoS2/gC3N4/graphene ternary nanocomposite for photocatalytic CO2 reduction to hydrocarbon fuels: In aqueous solvents with a sacrificial donor

MoS2/gCN/graphene ternary nanocomposites were synthesized using the ultrasonication-assisted calcination method, and different amounts of gCN were loaded to prepare the ternary nanocomposites. The hybrid MoS2/gCN/graphene ternary nanocomposites showed significant responses to an incident light source, and electrochemical analysis indicated that the junctions of the rose-like MoS2, metal-free gC3N4, and 2D graphene positively changed the electronic structure without changing the internal crystal and electronic structures of each unary nanocomposite, thus offering an effective separation of the electron–hole pairs. Therefore, this process provides abundant photoinduced electrons for CO2/CH3OH and holes for the water oxidation reactions, which can in turn be employed for the photoreduction of CO2. In addition, the charge-carrier mechanism of the ternary nanocomposites was labeled as type-II heterojunction. The use of an aqueous solvent with a basic salt and donor scavenger enhanced the Type-II heterojunction photocatalytic CO2 reduction because of the efficient supply of hydrated CO2 molecules and the large number of electrons required for the complex reduction reaction of CO2 to alcohol. Control of the external and internal factors for photocatalytic CO2 reduction further increased the selectivity for the reduction of CO2 and CH3OH. This work demonstrates the successful integration of gCN, graphene, and rose-like MoS2 with enhanced catalytic activity. Moreover, this work is expected to be of great importance in the development of photocatalyst materials for CO2 reduction while allowing advanced tunable chemical and structural properties of the metal-free gCN and rose-like MoS2.

Tailoring interfacial S-scheme heterojunction and porous ternary nanocomposite: Its highly efficient CO2 reduction in an aqueous solution

A calcination-assisted hydrothermal method was used to successfully prepare a series of porous boron nitride/Cu/Al2O3 composites. All of these nanocomposites were found to have efficient separation and migration for photoexcited electron-hole pairs, which provide an abundance of photoinduced electrons for the CO2 redox reaction and holes for the water oxidation reaction, which can be used for the photoreduction of CO2. The charge carrier process of the pBN/Cu/Al2O3 nanocomposites labeled as the S-scheme heterojunction system contributed to the prompt separation and transfer of photogenerated charge carriers. The introduction of porous boron nitride (pBN) supplies adsorbed CO2 to the surface of Cu/Al2O3 while suppressing undesirable side reactions. The addition of the basic salt NaHCO3 enhances S-scheme CO2 reduction because of the efficient supply of hydrated CO2 molecules to the photocatalyst surface. Thus, the photocatalytic CO2 reduction test further confirmed that the formation of the hybrid pBN/Cu/Al2O3 efficiently increases the methanol production rate. The excellent photocatalytic properties of pBN/Cu/Al2O3 are anticipated to be of great significance for the development of photocatalyst materials for CO2 reduction tests, as well as the tunable chemical and structural properties of pBN at advanced levels, given the electrochemical and surface structural tunability of pBN/Cu/Al2O3.

Alkali salts of amino acids as alkaline additives for neutralization of acidic corrosion inhibitors

We present alkali salts of amino acids as functional, non-toxic, non-hazardous, non-volatile, chemically stable, and cheap alkaline additives for common acidic corrosion inhibitors. The resulting mixtures have been evaluated for Co, Ni, and Cu leaching and were analyzed by chip filter assay, potentiodynamic polarization measurements, electrochemical impedance measurements, and gravimetry for corrosion protection of iron and steel in aqueous environment at slightly alkaline pH. Leaching of Co and Ni was found to depend on the corresponding complex stabilities. Taurine (Tau) as well as aminohexanoic acid (AHX) leads to low leaching of Co and Ni. Particularly AHX is an attractive low leaching additive leading to lower Co and Ni concentrations in solution than currently used amino alcohols. Glu and Tau were found to synergistically interact with several acidic corrosion inhibitors of the carboxylic acid and the phosphonic acid type. Tau had a particularly positive impact on the protective properties of carboxyphosphonic acids. Glu had also a positive effect on the anti-corrosive properties of several acidic corrosion inhibitors and served as an anti-scalant. Alkali salts of Glu and Tau might thus serve as commercially and ecologically attractive substitutes for current alkaline additives to acidic corrosion inhibitors.

Investigation of the mechanism of nickel hydroxide formation from nickel nitrate

Nickel hydroxides are widely used as electrochemically active substances in alkaline batteries and hybrid supercapacitors; they can be used for electrocatalysis, in electrochemical sensors, and as pigments. Knowledge of the formation mechanism of nickel hydroxides is necessary for developing and optimizing targeted synthesis methods. The thermal effects of processes in the formation of nickel hydroxide from nitrate were studied by the calorimetry method. The mechanism of precipitate formation was investigated by the method of simultaneous potentiometric (with a glass universal electrode) and conductometric titration. The nickel content in the samples obtained at the determined NaOH/Ni2+ ratios was investigated by the chemical method of trilonometry after preliminary dissolution. Calorimetric investigations showed that the reaction of nickel nitrate with NaOH was exothermic with ΔНreaction=‒28328.5 J/mol. The exothermic nature of the NaOH dilution process was revealed with ΔНdilution =‒2454 J/mol. According to the results of potentiometric titration, the formation of a basic salt of the NiOHNO3 type was not detected. Analysis of the results of conductometric titration revealed a two-stage chemical mechanism for the formation of nickel hydroxide from nitrate. At the first stage, which had a high rate, due to the liquid-phase reaction of the nickel cation with the hydroxyl anion, a primary precipitate of the composition Ni(OH)1.87(NO3)0.13 was formed. In the second stage, as a result of a slow topochemical reaction of the primary precipitate with hydroxyl anions, nitrate ions were displaced from the precipitate to form nickel hydroxide. These data are confirmed by the analysis of precipitate obtained at NaOH/Ni2+ ratios of 1.87 and 2.2: the Ni content was 52.95 % and 55.63 %, corresponding to the formulas Ni(OH)1.87(NO3)0.13∙0.68H2O and Ni(OH)2∙0.71H2O. This clearly indicated that the primary precipitate was nitrate-doped α-Ni(OH)2 and the final precipitate corresponded to the α-modification of nickel hydroxide

Design and Validation of an Experimental Setup for Evaluation of Gas Permeation in Ceramic Membranes

An experimental setup for the evaluation of permeation of gaseous species with the possibility of simultaneously collecting electrochemical impedance spectroscopy data in disk-shaped ceramic membranes was designed and assembled. It consists of an alumina sample holder with thermocouple tips and platinum electrodes located close to both sides of the sample. Water-cooled inlet and outlet gas connections allowed for the insertion of the sample chamber into a programmable split tubular furnace. Gas permeation through a ceramic membrane can be monitored with mass flow controllers, a mass spectrometer, and an electrochemical impedance analyzer. For testing and data validation, ceramic composite membranes were prepared with the infiltration of molten eutectic compositions of alkali salts (lithium, sodium, and potassium carbonates) into porous gadolinia-doped ceria. Values of the alkali salt melting points and the permeation rates of carbon dioxide, in agreement with reported data, were successfully collected.

Mechanism of coupling corrosion caused by flue gas and deposits in municipal solid waste incinerator: Resistance of HVOF-NiCr coating

Municipal solid waste (MSW) incineration technology have developed rapidly for the achievement of waste disposal and energy conversion. However, the contents of alkali salts especially chlorides are much higher than traditional solid fuels such as coal and biomass, resulting in severe high-temperature corrosion. High-velocity oxy-fuel spray (HVOF) coating is a promising method, while the complex corrosion process involving flue gas and deposits was still unclear. In this study, the in-service performance and coupling corrosion mechanism was investigated. After the 2700 h of in-situ experiments in a 400 t/d MSW incinerator, thickness loss of bare high temperature superheater was 1.9 times that of bare low temperature superheater. For coated superheater by HVOF-NiCr coating, the layered Cr, Mo and Ni oxides was successively formed during the corrosion process, contributing to an 80 % reduction in the thinning rate. In order to further investigate the corrosion mechanism induced by deposits and flue gas, the decoupling analysis of corrosion kinetics and in-stage characterization was conducted based on the lab-scale experiments. Results showed that a two-stage linear fitting was appropriate, theoretically confirming that the coupling corrosion reaction is dominated by deposits. HCl and SO2 can significantly accelerate the deposits-induced corrosion by about 10 times, through promoting the inward penetration of chlorine and oxidation. The resistance of HVOF-NiCr coating against corrosion can be divided into two stages. In the first 10 h, the growth of spherical nickel oxide with continuous oxygen intake resulted in a quick mass gain rate of 1.18 mg·cm−2·h−1. Subsequently, the corrosion rate significantly decreased to 0.086 mg·cm−2·h−1 due to the formed oxide layer. This study provided a new insight into the coupling corrosion caused by flue gas and deposits through kinetic analysis, and the resistance of HVOF-NiCr coating was clarified through the staged characterization.

Investigating pH and other electrical properties of potassium salt solutions

A recent study of ours reported that pH of common salts varies with concentration at room temperature. It can either increase in case of basic salts or decrease in case of acidic salts. In this study, pH values of four kind of potassium salts were investigated and their pH values increased with salt concentrations. It was reasoned that the concentration of hydrogen ions equalled the concentration of positive charges/protons in a solution, so a relationship between the activity of hydrogen ions and charge activity was developed. Further, the well-established equations for pH with hydrogen-ion activity and electrostatic/cell potential were extended to charge activity. Potential energy, the product of charge activity and electrostatic/cell potential, was presented and discussed.

Improving the Quality of People's Salt Using the Blue Economy Concept in East Java Province, Indonesia

Assessment of the quality of people's salt in East Java Province is only seen based on color and shape, even though the NaCl level determines whether or not the quality of the salt is good. Implementing the production process is often counterproductive, with reusing "bittern" for production affecting quality. Still, some also throw away "bittern" which can cause ecosystem pollution, contrary to the blue economy concept. This study aims to determine the quality control of people's salt, the implementation of blue economy principles in the salt sector, and solutions to improve the quality of people's salt in East Java Province by considering the blue economy principles. The research approach uses mixed methods with quantitative descriptive and qualitative descriptive. Data is collected through interviews, observation, documentation, and audio and visual materials. Quantitative descriptive data analysis techniques used statistical process control and capability analysis, while qualitative descriptive data analysis used the Interactive Model, including data condensation, data display, and conclusion drawing/verification. The results of this study indicate that it must improve people's salt quality control in East Java Province because the average is still in the K3 quality category. NaCl levels < 85% and 85%-89.99% and Mg levels 0.080%-0.099% are a top priority for quality control. Analysis of process capability shows that production is inadequate, and the people's salt in East Java Province has not been able to meet the quality standards for iodized consumption salt and industrial salt for various foods due to personnel, measurements, methods, materials, and environmental factors. Solutions to improve the quality of people's salt by referring to the blue economy principle through increasing the competence of farmers, preparing production SOPs, applying semi-modern production technologies, improving techniques for transferring water and raw materials, washing and recrystallization, providing assistance with production facilities, technical guidance, and having a policy for determining salt as a basic need and salt commodity reference price.

Reactivity of C3S and model cement in presence of Na2S2O3 and NaSCN

The impact of NaSCN and Na2S2O3 on the reactivity, microstructure and morphology of C3S and model cement (with a clinker containing 85% C3S and 15% C3A) pastes was systematically investigated. Results concluded that both alkali salts mainly act enhancing the reactivity of the C3S phase while not significant influence on the reactivity of C3A was measured. While both admixtures rose the reactivity of C3S over the studied 7 days of hydration, they only increased the reactivity of model cement pastes up to 14–20 h. NaSCN and Na2S2O3 did not modify the C–S–H stoichiometry but they influenced its morphology. In particular, thicker convergent C–S–H needles were formed in pastes containing Na2S2O3 compared to non-admixed systems, while a higher number of thinner C–S–H needles were formed in presence of NaSCN. Furthermore, greater portlandite clusters and intermixing of AFm and C–S–H were observed in admixed C3S and model cement pastes, respectively, compared to plain systems.

Substrate-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry of Some Small Biomolecules Using TiO2-Nanotubes: The Effect of Nanotube Diameter and Salt Addition.

Substrate-assisted laser desorption/ionization (SALDI) is a kind of soft ionization method that is most suitable for the analysis of low molecular weight analytes when it is coupled with a time-of-flight mass spectrometer. Unlike the conventional matrix-assisted laser desorption/ionization, there is no interference in the SALDI with matrices for the low mass analyte peaks (m/z < 700). The focus of this work is to develop substrates based on nanomaterials to obtain higher sensitivity, better reproducibility, and easier preparation. The mass spectra of some small molecules (capecitabine, hemin, methadone, noscapine, oxycodone, thebaine, malathion, chlorpyrifos, ethion, permethrin, and phosalone) deposited on the TiO2-nanotube (TiO2-NTs) plate by the SALDI-TOF-MS technique are reported. The nanotubes are synthesized in different diameter sizes of nanotubes via the anodizing method. The intensity of the analyte peaks and the softness of ionization are optimized by varying the diameter of nanotubes and adding relevant alkali salts to the analytes. In addition, the reproducibility of the signal intensity of analytes is optimized by changing the surface hydrophilicity of the TiO2-NT plate.

Mitigating Electrode Inactivation during CO2 Electrocatalysis in Aprotic Solvents with Alkali Cations

CO2 electrochemical reduction (CO2R) in aprotic media is a promising alternative to aqueous electrocatalysis, as it minimizes the competing hydrogen evolution reaction while enhancing CO2 solubility. To date, state-of-the-art alkali salts used as electrolytes for selective aqueous CO2R are inaccessible in aprotic systems due to the inactivation of the electrode surface from carbonate deposition. In this work, we demonstrate that an acidic nonaqueous environment enables sustained CO2 electrochemical reduction with common alkali salts in dimethyl sulfoxide. Electrochemical and spectroscopic techniques show that at low pH carbonate buildup can be prevented, allowing CO2R to proceed. Product distribution with a copper electrode revealed up to 80% Faradaic efficiency for CO2R products, including carbon monoxide, formic acid, and methane. By understanding the mechanism for electrode inactivation in an aprotic medium and addressing that challenge with dilute acid addition, we pave the way toward the development of more efficient and selective electrolytes for CO2R.