Aqueous Potassium Hydroxide Solution Research Articles

Functionalized Silicone Elastomer via Alkaline Solution to Coat Phosphorylcholine-Based Copolymer Containing Organosilane to Improve Hemocompatibility for Medical Devices

Surface modification of hemocompatible copolymers on silicone elastomers (SEs) is crucial for the long-term use of medical devices. Both physical adsorption and chemical conjugation are important for modification of SE. Oxygen plasma treatment is widely used to produce silanol groups on SE for silane coupling. However, the plasma reaction is difficult to apply to the surface modification of three-dimensional complex devices. This study demonstrated an appropriate and efficient method with alkaline solution for producing silanol groups on SE for modifying phosphorylcholine-based copolymer with organosilane (cross-MPC copolymer). A 2.5 wt% aqueous solution of potassium hydroxide (KOH) was effective in producing silanol groups and for coating the cross-MPC copolymer. Additionally, we successfully modified the cross-MPC copolymer on the inner surface of SE tubes after pretreatment with the 2.5 wt% KOH aqueous solution, and the copolymer film was coated homogeneously. The cross-MPC copolymer film on SE was stable for one month under fluidic condition with a shear stress of 3.2 Pa. The hollow fiber membrane with the polymer coating inhibited blood coagulation after one week implantation with extracorporeal circulation device using a goat. Therefore, pretreatment of SE using an alkaline solution is an appropriate method for producing silanol groups for coating the cross-MPC copolymer by silane-coupling reaction.

Alkaline Extraction of Organomineral Potassium Humate from Coal Mining Waste

Organomineral potassium humate was extracted from coal mining waste from the Lenger deposit (Turkestan region, Kazakhstan) by alkaline extraction using an aqueous solution of potassium hydroxide. The time and temperature of the process were investigated for the degree of extraction and yield of the product. A comprehensive study of the physicochemical properties of the raw material and the resulting production potassium humate was carried out by chemical analysis, scanning electron microscope, energy dispersion, IR-Fourier spectrometric and X-ray diffractographic analyses. The maximum degree of extraction and yield of the product wasachieved at 80 °C and 90 min. Moreover, the experimental data were subjected to kinetic processing, as a result of which it was established that the process of extraction of potassium humate occurs in the external diffusion region.

Electrodeposited nickel–zinc alloy nanostructured electrodes for alkaline electrolyzer

Over the last decade, as a consequence of the global decarbonization process, the interest towards green hydrogen production has drastically increased. In particular a substantial research effort has focused on the efficient and affordable production of carbon-free hydrogen production processes. In this context, the development of more efficient electrolyzers with low-cost electrode/electrocatalyst materials can play a key role. This work, investigates the fabrication of electrodes of nickel-zinc alloys with nanowires morphology cathode for alkaline electrolyzers. Electrodes are obtained by the simple method of template electrosynthesis that is also inexpensive and easily scalable. Through the analysis of the morphological and chemical composition of nanowires, it was found that the nanowires composition is dependent on the concentration of two metals in the deposition solution. Electrocatalytic tests were performed in 30% w/w potassium hydroxide aqueous solution at room temperature. In order to study the electrodes stability, mid-term galvanostatic test was also carried out. All electrochemical tests show that nanowires with about 44.4% of zinc have the best performances. Particularly, at −50 mAcm−2, these electrodes have an overpotential 50 mV lower than pure Ni nanowire. NiZn nanowires show also a good stability over time without noticeable signs of performance decay.

Synthesis, characterization and crystal structure of some novel partially hydrogenated isoquinolines and their fused heterocyclic systems

AbstractKetonic hydrolysis of 7‐acetyl‐4‐cyano‐1,6‐dimethyl‐6‐hydroxy‐8‐phenyl‐5,6,7,8‐tetrahydro‐isoquinoline‐3(2H)‐thione (1) via heating with aqueous solution of potassium hydroxide resulted in both deacetylation and dehydration affording new 7,8‐dihydroisoquinoline scaffold (7,8‐DHISQ) 2. Two simple mechanistic approaches are postulated for this synthesis. One of them was supported by converting 7‐acetyl‐4‐cyano‐1,6‐dimethyl‐8‐phenyl‐7,8‐dihydroisoquinoline‐3(2H)‐thione (3) into 7,8‐DHISQ 2 via heating with aqueous solution of potassium hydroxide. Compound 2 was used as a key intetermediate for synthesizing other 7,8‐DHISQ's 4 and 6, as well as 7,8‐dihydrothienoisoquinoline 7. Reaction of compound 3 with 2‐chloroacetamide (8) by refluxing in ethanol containing sodium acetate gave 7‐acetyl‐1‐amino‐5,8‐dimethyl‐6‐phenyl‐6,7‐dihydrothieno[2,3‐c] isoquinoline‐2‐carboxamide (10) which was converted into full aromatized pyrimidothienoisoquinoline 12 on treatment with triethyl orthoformate. Reaction of 3 with both hydrazine hydrate and hydroxylamine hydrochloride afforded tetrahydropyrazolo‐isoquinoline 13 and tetrahydroisoxazoloisoquinoline 14, respectively. Reaction of 14 with N‐(4‐chlorophenyl)‐2‐chloroacetamide (15) produced (N‐phenylcarbamoylmethylthio)tetra‐hydroisoxazoloisoquinoline 16 which was coverted into tetrahydroisoxazolothieno‐isoquinoline 17 upon heating with sodium ethoxide. Also, crystal structures of compounds 4 and 13 were determined via X‐rays diffraction analysis.

Вплив природи електроліту на електрохімічні властивості вуглецевого матеріалу рослинного походження

Non-aqueous electrolytes are advantageous for power sources due to the increase in the operating voltage since their electrochemical stability range is much wider. It should be noted that the capacitor’s capacitance depends on the capacitance provided by the electrode material, expressed in F/g, while its voltage and resistance depend on the electrolyte. Therefore, it is very important to study the electrochemical properties of carbon material in aqueous and organic electrolytes and to determine the effect of the electrolyte on the capacitance of the capacitor formed on its basis. The cathode mixture was made of porous carbon material obtained from biomass and a binding additive. Then, it was pressed onto a nickel grid with an area of 0,5 cm2. A 30% aqueous solution of potassium hydroxide (KOH) and a 0,7-molar solution of tetraethyl ammonium tetrafluoroborate ([C2 H5 ]4 NBF4) in acetonitrile (CH3CN) was used as the electrolyte. The measurements were carried out using two- and three-electrode schemes with a silver chloride reference electrode. Modeling impedance data to equivalent electrical circuits has assisted to establish the influence of the volume charge region in the electrode material on the capacitor’s capacitive characteristics. The specific capacitance values of 125 F/g in KOH and 101 F/g in [C2 H5 ]4 NBF4 are determined by the electrolyte type used and the nature of salts and bases dissolved in it. The practical significance of the obtained results is the application of the developed methods for obtaining carbon material with developed micro- and mesoporous structures and improved physicochemical properties.

Experimental evaluation of dynamic operating concepts for alkaline water electrolyzers powered by renewable energy

Synthetic current density profiles with wind and photovoltaic power characteristics were calculated by autoregressive-moving-average (ARMA) models for the experimental evaluation of dynamic operating concepts for alkaline water electrolyzers powered by renewable energy. The selected operating concepts included switching between mixed and split electrolyte cycles and adapting the liquid electrolyte volume flow rate depending on the current density. All experiments were carried out at a pressure of 7 bar, a temperature of 60 °C and with an aqueous potassium hydroxide solution with 32 wt.% KOH as the electrolyte. The dynamic operating concepts were compared to stationary experiments with mixed electrolyte cycles, and the experimental evaluation showed that the selected operating concepts were able to reduce the gas impurity compared to the reference operating conditions without a noticeable increase of the cell potential. Therefore, the overall system efficiency and process safety could be enhanced by this approach.

Effect of Mass Transport on the Charge Storage Mechanism of Cobalt Hydroxide Nanosheets in an Aqueous Electrolyte

Although cobalt hydroxide (Co(OH)2) has received great attention as a layered electrode material for aqueous-based energy storage applications due to its high theoretical capacity, it is unstable and easily oxidized to be more stable phase in an aqueous medium. This leads to decrease in capacity and cycling performance, limiting its practical application. In addition, a wide range of electrolyte concentration (1-6M) has been utilized for Co(OH)2 electrode and the mechanisms related to charge storage performance were still unclear. To enhance the overall performance, a deep understanding of charge storage mechanisms of Co(OH)2 corresponding to mass transport and electrolyte concentration is needed. Herein, the hydrodynamic voltammetry experiment using rotating disk electrode (RDE) was performed to study the effect of mass transport of the ions in electrolytes on the charge storage mechanism of the as-electrodeposited cobalt hydroxide nanosheets in various concentrations of an aqueous potassium hydroxide (KOH) solution. The cycling performance related to rotation rates and electrolyte concentrations was also studied. Additionally, Operando X-ray absorption spectroscopy (XAS) was carried out to investigate the change in oxidation state of Co(OH)2 in different concentrations of KOH during charge/discharge processes. The set of information in this work will pay the way for further development of the cobalt-based energy storage technologies.

Facile and Straightforward Synthesis of Racemic Version of Substituted 3-[3-(2-Hydroxyphenyl)-3-oxo-1-arylpropyl]-4-hydroxycoumarins: Easy Access to a Series of Biorelevant Warfarin Analogues

AbstractThe present communication deals with a straightforward, efficient, and green synthesis of a series of racemic version of 3-[3-(2-hydroxyphenyl)-3-oxo-1-arylpropyl]-4-hydroxycoumarins as biologically interesting warfarin analogues upon decarboxylative hydrolysis of bis-coumarin derivatives in aqueous potassium hydroxide solution. The salient features of this practical method are operational simplicity, avoidance of any organic solvents and tedious column chromatographic purification, clean reaction profiles, excellent yields, and gram-scale synthetic applicability.

Design of efficient solar photocatalytic system for hydrogen production and degradation of environmental pollutant

Here, we have designed an efficient multipurpose photocatalytic system based on iron-doped tin oxide (Fe-SnO2) which exhibited excellent catalytic activity toward dyes degradation and hydrogen production. The synthesized photocatalyst was characterized using different spectroscopic techniques. Fe-SnO2 was tested in degradation of different dyes i.e., congo red (CR), acridine orange (ArO) and methyl orange (MO) and among these dyes, Fe-SnO2 was more efficient and selective toward CR which was degraded more than 95% in 30 min. Further, the catalytic efficiency of Fe-SnO2 was also evaluated toward photocatalytic hydrogen generation from aqueous solutions of methanol, ethanol, propanol, potassium hydroxide and Na2S + Na2SO3, where Fe-SnO2 displayed high catalytic activity toward hydrogen generation from methanol solution under sunlight. Moreover, the catalytic activity of Fe-SnO2 toward CR degradation and hydrogen production was optimized by using different combinations of operating conditions and no major loss in activity was observed upon running the same photocatalyst sample in different batches.

Synthesis and characterization of potassium-doped multilayer graphene prepared by wet process using potassium hydroxide

Potassium (K) doping of multilayer graphene was demonstrated by means of a wet chemical process using potassium hydroxide (KOH) aqueous solution (KOH treatment). The presence of K atoms along the stacking direction was confirmed from depth profiles of 41K+ ions obtained by time-of-flight secondary ion mass spectroscopy (TOF-SIMS). The intensity images of 41K+ ions obtained by TOF-SIMS suggested that the K atoms existed throughout the whole area. For the KOH-treated multilayer graphene, no peak due to K intercalation between graphene layers was obtained by x-ray diffraction (XRD); in Raman spectra, splitting of the G-band peak and disappearance of the 2D-band peak were not observed. A graphite intercalation compound structure was not determined by either XRD or Raman results. However, the up-shift in the G-band peak position in the Raman spectra suggested that K atoms were doped in the graphene. X-ray photoelectron spectroscopy carbon 1s spectra implied that KOH treatment resulted in K-termination at the edges and/or domains of graphene. In addition, a C1s shoulder peak appeared at 1 eV higher binding energy compared to the C1s peak of pristine graphene. Temperature-dependent conductivity measurement results indicated that the conductivity of multilayer graphene was increased by KOH treatment. In addition, the conductivity increased with increasing temperature, which could be explained by band overlap.

CO2 absorption into potassium hydroxide aqueous solution: experimental and modeling

CO2 absorption into potassium hydroxide aqueous solution: experimental and modeling

Construction of dual metal ferrite-based core-shell nanostructures as low-cost multimetal electrode for boosting energy density of flexible asymmetric supercapattery

We report the synthesis and fabrication of economically cheaper and binder-free hierarchical core-shell nanostructures of copper ferrite nanorods and nickel ferrite nanosheets (CuFe2O4–NR@NiFe2O4–NS) via a two-step wet chemical technique. The unique core-shell (nanorods@nanosheets) nanostructures offer multiple redox couples (Cu2+, Fe3+, and Ni2+), smaller ion diffusion path, and faster electron movement. When evaluated as an individual electrode in aqueous potassium hydroxide solution, the as-synthesized CuFe2O4–NR@NiFe2O4–NS electrode demonstrate superior electrochemical behaviour with concurrent specific capacity of 1366 C g−1 at current rate 1 A g−1, and 94% capacity retention over 10,000 cycles. A flexible asymmetric supercapattery device is assembled comprising positive electrode of CuFe2O4–NR@NiFe2O4–NS and negative electrode of reduced graphene oxide (rGO) with PVA-KOH semisolid electrolyte. The ASC cell manifest enhanced specific energy of 72 Wh kg−1, specific power of 0.287 kW kg−1 and outstanding cycle life (~97% of retention over 10,000 cycles at 10 A g−1). The superior specific capacity, capacity retention, and excellent cyclic life endow such multimetal ferrite-based core-shell architecture with tremendous potential for use as electrode materials for fabricating next generation energy storage devices.

Concentration-dependent diffusion of lithium, sodium, potassium, and cesium hydroxides in water

The diffusion coefficients of aqueous solutions of lithium, sodium, potassium, and cesium hydroxide in a concentration range of 0 to 3.0 mol/L were obtained at 25 °C and normal pressure. The Fizeau interferometer and the spatial phase-shifting method were used to measure the spatial distribution of concentration of the investigated substances. The concentration dependence of the diffusion coefficient was determined from the Matano-Boltzmann analysis. The experimental setup and techniques, as well as the image and data processing procedure, were tested using an aqueous solution of nitric acid. The comparison made for lithium, sodium, and potassium hydroxides indicated good agreement between the obtained results and the data collected from the literature. The concentration dependence of the diffusion coefficient for cesium hydroxide in water was found experimentally for the first time.

Enhancing the performance of carbon electrodes in supercapacitors through medium-temperature fluoroalkylation

Medium-temperature fluoroalkylation of microporous activated carbons (ACs) with 1,1,1,2-tetrafluoroethane is presented. Supercapacitor (SC) electrodes based on the fluoroalkylated ACs showed enhanced specific capacitance and high specific energy in electrolytes, either aqueous potassium hydroxide solution or tetraethylammonium tetrafluoroborate-acetonitrile solution. We found the largest increase in the specific capacitance, up to 89 F g–1, and in the specific energy, up to 7.5 Wh kg–1, at the voltage of 1.5 V. The specific capacitance of the SC electrode based on the sample prepared at 350 °C increases by a factor of ~ 2–3 × for certain scan rates in the organic electrolyte. The fluoroalkylated ACs have good electrochemical stability in the tested model systems. We associate the registered enhanced SC parameters with an increase in the total fluorine content and high specific surface areas of the carbon electrode materials. The surface “isolated fluorine” formed during fluoroalkylation at 300–400 °C ensures the production of improved electrode materials for SC applications. Fluoroalkylation is a simple and cost-effective method of improving the specific capacitance of carbon-based SC electrodes.

Süperkapasitör elektrot için MnCo2S4 nanotellerin iki aşamalı sentezi

In this study, MnCo2S4 nanowires were synthesized on 3D-Ni foam by the hydrothermal process in two-step and investigated as supercapacitor electrode material. Crystal structure and morphology analyzes of MnCo2S4 nanowires were performed. Electrochemical measurements were taken in 1 M of a potassium hydroxide aqueous electrolyte solution. The specific capacitance value calculated from GCD measurement taken at a current density of 0.5 A g−1 from the sample was 450 F g−1. Furthermore, the sample have good cycling stability by keeping 46% of the initial specific capacitance after 3000 cycles.

Ni alloy nanowires as high efficiency electrode materials for alkaline electrolysers

The fabrication and characterization of nickel-alloy electrodes for alkaline electrolysers is reported. Three different alloys (Ni–Co, Ni–Zn and Ni–W) at different composition were studied in order to determine the optimum condition. Nanostructured electrodes were obtained by template electrodeposition into a nanoporous membrane, starting from aqueous solution containing the two elements of the alloy at different concentrations. Composition of alloys can be tuned by electrolyte composition and also depends on the difference of the redox potential of elements and on the presence of complexing agents in deposition bath. Electrochemical and electrocatalytic tests, aimed at establishing the best alloy composition, were carried out for hydrogen evolution reaction. Then, test conducted at a constant current density in potassium hydroxide (30% w/w) aqueous solution were also performed. For all investigated alloys, very encouraging results were obtained and in particular Ni–Co alloys richer in Co showed the best performance.

A Comparative Analysis of PEM and Alkaline Water Electrolyzers

There are two main industrial techniques of water electrolysis operating under near-ambient temperature and pressure conditions: alkaline water electrolysis which uses a liquid electrolyte based on an aqueous solution of potassium hydroxide [1] and PEM water electrolysis [2] which uses a solid electrolyte made of a proton-conducting polymer. Both technologies present a set of strengths and weaknesses in view of practical application in the industry sector. The objective of this communication is to highlight the differences and similarities in terms of design (cell and stack) and balance-of-plant, and to present in a critical way what are these advantages and disadvantages, from a scientific viewpoint (that of materials science, especially for the selection of electrocatalysts), from a technological viewpoint (stack design and balance-of-plant) and from an economic viewpoint (comparative analysis of capex and opex). The discussion will take into account the situation which prevails on machines at the MW-scale. Particular attention will be paid to the ability of these machines to operate under transient conditions, in particular with a view to providing services to the electricity network. Several performance indicators such as the flexibility and reactivity of machines to the demands of network operators will be used to carry out this comparison. A detailed analysis of the existing limitations will make it possible to define a set of development perspectives highlighting possible complementarities.[1] N. Guillet and P. Millet, in : Hydrogen Production: by Water Electrolysis’, chapter 4, Alkaline Water electrolysis, A. Godula-Jopek, D. Stolten Editors, Wiley-VCH (2015).[2] D. Bessarabov and P. Millet in: PEM water electrolysis, “Hydrogen and Fuel Cells Primers”, B.G. Pollet Editor, 1st Edition, Elsevier (2018).

Reversal Trend of Hounsfield Unit Values of Substances with High and Low Effective Atomic Numbers

Introduction: In dual-energy computed tomography (DECT), the Hounsfield values of a substance measured at two different energies are the basic data for finding the chemical properties of a substance. The trends of Hounsfield unit (HU) alterations following the changes in energy are different between the materials with high and low Zeff. The present study aimed to analyze the basic principles related to the attenuation coefficient of x-ray photons and a quantitative explanation is given for the mentioned behavior or trend. Material and Methods: A mathematical expression was derived for the HU difference between two different scanner voltages. Attenuation coefficients of diverse substances, such as methanol, glycerol, acetic acid, the aqueous solution of potassium hydroxide, and water were calculated for x-ray scanners operating differently at distinct applied voltages and with diverse inherent or added filters. Results: Findings of the current study demonstrated that the negative or positive outcome of HU(V1) - HU(V2) equation is not determined by the electron density of a substance. However, it is affected by the effective atomic number (Zeff) of the material and machine parameters specified by the source spectrum. Conclusion: According to our results, the sign of HU difference [HU(V1) – HU(V2)] for the variable cases of V2 and V1 gives an indication of the effective atomic number of the material under study. The obtained results might be of diagnostic value in the DECT technique.

Gas discharge between two liquid electrolyte electrodes

A gas discharge between two liquid electrolyte electrodes was studied experimentally in the current range of 0.5-3.5 A. As liquid electrolytes, aqueous solutions of sodium chloride, sodium carbonate, potassium hydroxide and copper sulfate, as well as tap water, were used. The effect of composition of electrolytes on characteristics of discharge was studied at different polarities of connection to the power source.

Growth, structural, optical and thermal studies of semi-organic nonlinear optical potassium hydrogen oxalate single crystal

Single crystals of semi-organic nonlinear optical material potassium hydrogen oxalate are grown from the aqueous solutions of potassium hydroxide and oxalic acid in 1:1 stoichiometric ratio by slow evaporation solution growth method at room temperature. The grown crystals are subjected to various characterization techniques to explore their structural explication, thermal, linear and nonlinear optical perspectives for optoelectronic device applications. The monoclinic structure with non-centrosymmetric space group P21/c of the titular compound has been confirmed by single-crystal X-ray diffraction. The crystal packing is ruled by extensive networks of hydrogen bonds revealed by the detailed study of the refinement of the crystal structure. Optical transparency of the crystal in the entire visible region has been confirmed by ultraviolet–visible-near infrared (UV–Vis-NIR) analysis. The robust thermal stability of the grown crystal is ensured by thermogravimetric–differential thermal analysis. The presence of expected functional groups in the grown crystal has been confirmed by Fourier transform infrared spectroscopic studies. Second-harmonic generation efficiency has been calculated by Kurtz powder method.