Aqueous Potassium Hydroxide Solution Research Articles

Oxygen Electrocatalysis of Perovskite Oxyfluorides in Alkaline Media

Introduction Fossil fuels are indispensable as the main energy source in modern society, but there are concerns about the environmental problems and depletion caused by increased use of them. To realize a sustainable society, high-performance energy conversion devices are required, and various secondary batteries are being developed. Among these, metal-air secondary batteries, which use atmospheric oxygen as the active material, are attracting a lot of attention. Their theoretical energy density are approximately 3 to 30 times higher than that of lithium-ion batteries.[1] At the air electrode of this battery, oxygen evolution reaction (OER) occurs during charging and oxygen reduction reaction (ORR) occurs during discharging, but the overpotentials of these reactions are high, which is an issue for practical application that needs high current density. Therefore, cost effective bifunctional catalysts that can promote both reactions are being extensively researched.Perovskites have high catalytic activity in alkaline solutions and are inexpensive compared to noble metal catalysts such as Pt and IrO2.[2] It has been reported that Ruddlesden-Popper-type layered perovskite oxychlorides showed high OER and ORR activities,[3] and this study focused on fluorine, which has high electronegativity. The purpose is to clarify the effects of partial fluorination of SrFeO3 -δ and SrCo0.8Fe0.2O3 -δ containing Fe, which is one of the 3d transition metal elements reported to have OER and ORR activity.[4] Experimental SrFeO3 -δ and SrCo0.8Fe0.2O3 -δ were synthesized by the sol-gel method.[5] Fluorination was performed by filling a fluororesin tube with the synthesized catalyst powder and fluorine gas at various pressures, and allowing it to stand overnight at room temperature or 100 °C. As for the characterization of the obtained catalyst, X-ray diffraction measurements were used to analyze the crystal structure, and a fluorine ion meter was used for the solution in which the catalyst powder was dissolved to quantify the amount of F- introduced.Catalytic activity was evaluated by using cyclic voltammetry (CV) measurements. The catalyst ink was prepared by dispersing the catalyst, acetylene black, and a cation-conducting ionomer (Nafion) in tetrahydrofuran. This catalyst ink coated on a glassy carbon rotating disk electrode was used as a working electrode. A platinum wire was used as the counter electrode, a reversible hydrogen electrode (RHE) was used as the reference electrode, and an oxygen-saturated 1 mol dm- 3 potassium hydroxide aqueous solution was used as the electrolyte. For OER activity measurement, the rotational speed of the working electrode was 1600 rpm, the scanning speed was 10 mV s- 1, and the scanning range was set from 1.1 V to 1.6 V vs. RHE, and measurements were performed for 50 cycles. For ORR activity measurement, the rotational speed of the working electrode was 1600, 1200, 800, and 400 rpm, the scanning speed was 10 mV s- 1, and the scanning range was set from 0.4 V to 1.0 V vs. RHE, and measurements were performed for 1 cycle at each rotational speed. Results As a result of X-ray diffraction measurements, it was confirmed that SrFeO3 -d and SrCo0.8Fe0.2O3 -d were synthesized before the reaction with F2. After the reaction, the peak positions were shifted, which confirmed that F- was doped, and it became clear that SrF2 was produced as an impurity.Figure 1 shows the results of CV measurements normalized by the electrochemically active surface area (ECSA) obtained in the potential range of 1.1 – 1.2 V vs. RHE (non-Faradaic reaction region) or electrode surface area. Regarding OER, the activity and cycling stability of SrFeO3 -δ decreased due to fluorination. Although the surface area of SrCo0.8Fe0.2O3 -δ increased due to fluorination, the activity normalized by ECSA decreased. Regarding ORR, it was confirmed that fluorination increased the electron transfer number and improved the ORR onset potential for all catalysts. Although the details are not clear so far, it is assumed that fluorination changes the valence of transition metal, local structure, and amount of oxygen vacancies, which may change the catalytic activity. Conclusion As a result of evaluating the catalytic activity of SrFeO3 -δ and SrCo0.8Fe0.2O3 -δ in which F- was doped, it was revealed that the OER activity decreased, but the ORR activity was improved.

Bioactive surface modification of Ti–Nb alloy by alkaline treatment in potassium hydroxide solution

Abstract The aim of this work is to compare the responsive behaviour of titanium, niobium and titanium–niobium alloy during alkaline treatment in forming alkaline titanate layer and their resultant bioactive properties. Titanium and niobium powder mixture with composition in the beta region was pressed at 550 MPa and sintered at 1,200 °C for 2 h. The alloy was soaked in potassium hydroxide aqueous solution at 60 °C for 24 h with different concentrations of 0.5 M and 5 M. The effect of post sintering-heat treatment was investigated by annealing the treated alloy at 600 °C for 2 h. X-ray diffraction analysis and Fourier transform infrared spectroscopy analysis were used to evaluate the chemical composition and the functional group of material on the treated alloy surface respectively. Immersion in Hanks solution for 1 day resulted in traces of calcium and phosphate on alloy surfaces treated in different concentrations of alkali as well as post-heat treatment. The cell viability evaluation using MTT (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) assay on the new beta-Ti alloy with potassium-based titanate layer demonstrated potassium hydroxide treatment with a 5 M concentration after post-heat treatment significantly improved cell proliferation, which is a prerequisite for bone mineral apatite deposition.

Carbon capture via electrochemically mediated alkaline absorption: Lab-scale continuous operation

Energy-efficient capture technologies need to be deployed by 2050 to abate global warming caused by excessive carbon dioxide (CO2) emissions. CO2 capture using alkaline solutions and absorbent regeneration mediated through bipolar membrane electrodialysis (BMED) have been tested previously as a standalone technology. However, the continuous operation of an integrated system remains largely unclear. Here, a bench-scale study was conducted using an integrated prototype to analyze the performance of CO2 capture and electrochemical regeneration using potassium hydroxide (KOH) aqueous solution. A wide range of current densities from 150 to 1000 A/m2 was applied to demonstrate the continuous operation of the CO2 capture system emphasizing the stability in attainable high rich carbon loading and CO2 desorption. The electrochemical regeneration module achieved CO2 desorption efficiency of 70% and absorbent recovery up to 89% under industrial relevant current densities of 500–1000 A/m2. The absorbent recovery has been identified to be a result of the combined effect of load ratio and rich carbon loading. The observed inefficient CO2 separation indicates significant potential to enhance energy efficiency. These results represent a pivotal step forward in electrochemically mediated CO2 capture technology, with promising potential for rapid industrial scale-up in the near future.

Stretchable supramolecular hydrogel with instantaneous self-healing for electromagnetic interference shielding control and sensing

Conductive hydrogels possess instantaneous self-healing and adhesive properties have generated great excitement in the fields of sensing and electromagnetic interference (EMI) shielding. In this study, we ingeniously designed hydrogel-based soft materials with high conductivity by using poly(vinyl alcohol) (PVA), positively charged Ti3C2Tx MXene and thioctic acid (TA) as source materials. Through concentration-induced ring-opening polymerization of TA monomers in an aqueous solution of potassium hydroxide (KOH), supramolecular poly(potassium thioctate) (poly(PT)) was obtained. Then, the multifunctional poly(PT)/PVA/p-MXene hydrogel with exceptional stretchability, substrate-adhesion and self-healing capability was achieved through abundant dynamic bonds, including disulfide bonds, hydrogen bonds, coordination bonds and electrostatic interactions. The hydrophobic main chains within poly(PT) provide robust protection against the oxidative degradation of MXene. This hydrogel shows outstanding strain sensing and extraordinary EMI shielding effectiveness (SE) of 48.56 dB caused by the inner structure, conductivity, and water content. Interestingly, the EMI SE can be regulated by reabsorbing moisture from the air, thereby enabling the reuse of dried hydrogel. Furthermore, the EMI SE can be dynamically modulated through controlled deformations, confirming the potential application for electromagnetic waves (EMWs) sensing. This innovative approach not only simplifies the fabrication of multifunctional materials but also expands the applications of adhesive hydrogels with conductivity.

Management of toxic waste released by incorrectly discarded batteries in Brazil

Abstract The main difference between a dry cell battery and an alkaline one is the composition of the electrolyte. In zinc–carbon batteries, dry cell, the electrolyte is a paste formed by mixing ammonium chloride and zinc chloride, whereas in alkaline batteries, the electrolyte is a concentrated aqueous solution of potassium hydroxide containing a certain amount of zinc oxide, hence the name alkaline for this battery. Therefore, the improper disposal of these materials has numerous consequences for the environment, since the potentially toxic metals present in them can be leached, infiltrating, and contaminating the soil layers, the groundwater, as well as the fauna and flora of the regions nearby. Thus, the objective is to perform studies that aim to simulate and analyze the release of potentially toxic metals present in batteries found in normal environmental conditions, through leaching tests from regular batteries (Zn–C) on fertilized soil, simulating a landfill, in addition to tests on sandy soil in order to aid the identification of possible waste release.

Dissolution dynamics of poly(4-hydroxystyrene) in potassium hydroxide (KOH) and sodium hydroxide (NaOH) aqueous solutions investigated by quartz crystal microbalance (QCM) method

Abstract The molecular size of alkaline cation has been reported to affect the dissolution of resist film in alkaline aqueous solution. However, the details are still unclear. In this study, the dissolution dynamics of poly(4-hydroxystyrene) (PHS) in potassium hydroxide (KOH) and sodium hydroxide (NaOH) aqueous solutions was investigated to clarify the effects of small alkaline cations on the dissolution dynamics of typical backbone polymer for chemically amplified resists by a quartz crystal microbalance (QCM) method. The temporal changes in the frequency and impedance of QCM substrates during development were measured. The maximum impedance reachable during development significantly exceeded that of the developer saturated with PHS unlike the case of tetramethylammonium and tetraethylammonium cations. This means that the PHS matrix near surface was swollen by decreasing the size of alkaline cation. By either increasing or decreasing the size of alkaline cation from tetramethylammonium and tetraethylammonium cations, the transient swelling layer became thick.

Photoconductivity in self-assembled CuO thin films

Self-assembly is the most promising low-cost and high-throughput methodology for nanofabrication. This paper reports the optimization of a self-assembly process at room temperature for the growth of copper oxide (CuO) based nanostructures over a copper substrate using aqueous potassium hydroxide (KOH) solution as the oxidizing agent. The monoclinic phase of CuO nanostructures grown over the copper substrate was confirmed from the X-ray diffraction (XRD) and micro-Raman analysis. The overall chemical composition of nanostructures was confirmed to be that of CuO from its oxidation state using X-ray photoelectron spectroscopy (XPS). Photodetectors were engineered with the structure Cu/CuO/Ag. The photodetectors exhibited a response to both ultraviolet and visible light illumination. The optimized Cu/CuO/Ag structure exhibits a responsivity of ~ 1.65 µA/W, with an ON:OFF ratio of ~ 69 under a bias voltage of 0.01 V. The temporal dependence of photo-response for the optimized photodetector displayed the persistent nature of photoconduction indicating a delay in charge carrier recombination which could potentially be exploited for photovoltaic applications.

Communication—Controlling Etching of Germanium through Surface Charge Manipulation

Potassium hydroxide (KOH) aqueous solutions can effectively etch germanium. Etch rates were determined in an electrolytic etch cell. Electrically isolated Ge wafers were subject to an etch rate of 1.45 ± 0.07 nm min−1, increasing to 12.6 ± 0.2 nm min−1 when grounded, 97 ± 2 nm min−1 when biased at −0.9 V, and 138 ± 2 nm min−1 with periodic biasing. Results suggest that the previously reported limited etching in KOH is associated with the recombination of holes with electrons injected from the surface reaction. The results of this study demonstrate that changing the hole concentration through biasing is an effective tool to control electrolytic etch rates, enabling future selective etching processes for germanium.

A COMPREHENSIVE REVIEW ON CHALCONE ANALOGUES-VERSATILE SCAFFOLD WITH MEDICINAL AND BIOLOGICAL POTENTIAL

This review’s main focus is on the most recent synthesis of chalcones with N, O, or S heterocycles, highlighting their biological potential. Chalcone derivatives are considered in beneficial species because they possess a keto-ethylenic moiety, CO−CH=CH−. Due to the existence of a reactive α, β-unsaturated carbonyl group, the synthesis of chalcone derivatives, which have been physiologically explored for use against specific disease targets, has been made possible by recent advances in heterocyclic chemistry. The need for novel drugs that are effective against multidrug-resistant pathogens has been driven by the growth in antibiotic resistance brought on by a variety of reasons. Chalcones are phenolic compounds that fall within the flavonoids category. They are a part of a large category of naturally occurring bioactive substances. During this review we have gone through a number of studies where chalcones were created via Claisen Schmidt condensation of suitable acetophenone with suitable aromatic aldehydes in the presence of an aqueous solution of potassium hydroxide and ethanol at room temperature in an effort to create antibacterial agents. The review content have been obtained through web browsing on various scientific databases and search engines like Science Direct, Pub Med, Research Gate, Google Scholar, etc. The synthesis of diverse chalcone derivatives was motivated by the potential activity of naturally occurring chalcones as anticancer, anti-inflammatory, antibacterial, antioxidant, and antiparasitic characteristics, as well as by their unique chemical structural structure. Flavonoids and isoflavonoids, which are frequent chemical building blocks found in a variety of naturally derived compounds, are enhanced by chalcone. This review may prove to be helpful for the creation and design of new powerful therapeutic medications.

Synthesis of black TiO2 nanotubes decorated biomass-derived spongy carbon as an electrode material for producing deionized water through capacitive deionization technology

The capacitive deionization (CDI) technique is considered a promising eco-friendly desalination method due to its high energy efficiency, ease of operation, and simplistic electrode regeneration capability. Thus, significant research is focused on developing highly efficient electrode materials with high electrochemical stability and salt electro-adsorption capacity (Sc) behavior during operation because these are the governing factors in examining the measured activity of fabricated CDI cells. In this manuscript, we report the synthesis of hydrogenated titanium nanotubes@spongy activated carbon (HTiO2 NTs@SAC) using pyrolysis and hydrothermal processes. The SAC is synthesized by the pyrolysis of spongy loofa in an inert atmosphere and further hydrothermally activating it in an aqueous potassium hydroxide solution. The hydrothermal process activates and enhances the hydrophilicity of SAC. HTiO2 is synthesized electrochemically at 20 V in 0.1 M perchloric acid. Such HTiO2 NTs@SAC configuration can provide excellent pathways to increase ion adsorption and improve the kinetics of charge transfer by enhancing the contact between the electrolyte and electrode at the interface. It is found that HTiO2 NTs@SAC has a specific capacitance (Cs) of 385.7 F g−1 compared with 332.7 F g−1 for SAC. The salt electrosorption capacity (Sc) of HTiO2 NTs@SAC electrode material is found to be 24.90 mg g−1 in 250 μS cm−1 saline solution at 1.2 V, which is much higher than the values obtained for SAC (9.8 mg g−1). HTiO2 NTs@SAC has also shown an antimicrobial effect toward gram-negative bacteria and exhibited good performance in the supercapacitor application, wherein HTiO2 NTs@SAC showed a higher Cs (505.55 F g−1) than SAC (380 F g−1) at 1 A g−1. Thus, we demonstrate that the prepared composite can be used as an energy storage material, an antibacterial material, and a CDI electrode in the CDI technology.

Simulation of carbon dioxide direct air capture plant using potassium hydroxide aqueous Solution: Energy optimization and CO2 purity enhancement

While various methods of direct air capture (DAC) technology have been implemented, its widespread effectiveness hinges on achieving optimal design and process improvements, largely owing to the high energy costs involved. Literatures reports a substantial heat demand for high-temperature aqueous solutions DAC (HT DAC), ranging from 1420 to 2250 kWh per ton of CO2, accompanied by electricity consumption rates varying from 366 to 2790 kWh per ton of CO2. The present study adopts the HT DAC method with an aqueous KOH absorbent as its focus, aiming to mitigate energy consumption. Given that a substantial portion of energy consumption in comparable processes can be attributed to the calciner and slaker units, our research centers its attention on the Air Separation Unit (ASU) and the steam cycle unit, investigating their impact on the system's production capacity, the enhancement of CO2 purity, and the augmentation of equipment thermal recovery. Process optimization, results a remarkable increase in heat recovery (21.1 %) and significant reductions in utilities consumption. The outcomes indicate that this facility has the capacity to annually capture around 1.1 million tons of CO2 with a purity of 99 mol% for utilization across various industries. The process design necessitates 5.24 gigajoules (GJ) of heat and 343 kW-hours (kWh) of electricity per ton of captured CO2. Notably, in addition to fulfilling the internal electricity requirements, the facility can export 8 MWh of electricity per ton of captured CO2 to the grid.

Obtention and characterization of nano bio-hydroxyapatite particles by combined hydrothermal alkaline and ultrasonic wet milling methods

This article deals with the extraction, recovery, and characterization of nano bio-hydroxyapatite particles (nBio-HAp) from pig bones obtained by hydrothermal alkaline treatment in combination with an ultrasonic wet milling process. Pig bone powder was defatted and deproteinized with an 1 N potassium hydroxide (KOH) aqueous solution for 24 h with stirring at 90 °C, followed by ultrasonic treatment pulsed at 100 W (Pulse-cycle: 70%) for 10, 20, 30, and 60 min. Fourier Transform Infrared spectroscopy (FT-IR) showed that the alkaline treatment removed the organic compounds from the mineral matrix. Dynamic Light Scattering (DLS) and Scanning Electron Microscopy (SEM) showed that the particle size decreased with increasing duration of ultrasound, indicating the mechanism of erosion and fragmentation of micro agglomerates into nanoparticles. The X-ray patterns showed that none of the methods used to clean and extract the nanoparticles (ultrasound) damaged the Bio-HAp nanocrystals. Full Width at Half Maximum (FWHM) and crystallite size proved that they have a size between 22 and 27 nm, which was confirmed by Transmission Electron Microscopy (TEM) in the form of platelets and bacilli. Inductively coupled plasma (ICP) showed the presence of Mg, Na, K, and Zn as minority ions and that the isolation processes of Bio-HAp nanoparticles do not affect their trace element concentrations.

Thin Film Composite Membranes as a New Category of Alkaline Water Electrolysis Membranes.

Alkaline water electrolysis (AWE) is considered a promising technology for green hydrogen (H2 ) production. Conventional diaphragm-type porous membranes have a high risk of explosion owing to their high gas crossover, while nonporous anion exchange membranes lack mechanical and thermochemical stability, limiting their practical application. Herein, a thin film composite (TFC) membrane is proposed as a new category of AWE membranes. The TFC membrane consists of an ultrathin quaternary ammonium (QA) selective layer formed via Menshutkin reaction-based interfacial polymerization on a porous polyethylene (PE) support. The dense, alkaline-stable, and highly anion-conductive QA layer prevents gas crossover while promoting anion transport. The PE support reinforces the mechanical and thermochemical properties, while its highly porous and thin structure reduces mass transport resistance across the TFC membrane. Consequently, the TFC membrane exhibits unprecedentedly high AWE performance (1.16 A cm-2 at 1.8V) using nonprecious group metal electrodes with a potassium hydroxide (25wt%) aqueous solution at 80°C, significantly outperforming commercial and other lab-made AWE membranes. Moreover, the TFC membrane demonstrates remarkably low gas crossover, long-term stability, and stack cell operability, thereby ensuring its commercial viability for green H2 production. This strategy provides an advanced material platform for energy and environmental applications.

The Performance of Chitosan-based Activated Carbon for Supercapacitor Applications towards Sustainable Energy Technologies

In sustainable technologies, the application of supercapacitors (SC) for energy conversion and storage systems is rapidly increasing. Supercapacitors are widely employed in applications that require fast charge and discharge phases, such as in the automobile industry, where they are utilized in energy storage. Chitosan (CS) is a natural polymer material utilized in supercapacitor fabrication. Interest in supercapacitors is due to their high-energy capacity, storage for a shorter period, and longer lifetime. In this research, the fabrication of symmetric supercapacitors with activated carbon (AC) electrodes has been investigated in order to analyze their performance characteristics. AC is derived from CS biomass, which has remarkable biodegradability. It has been chemically activated using ZnCl <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> as the activating agent. CS has been activated inside a furnace at 500, 600, and 700°C in an inert N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> atmosphere. A 1M aqueous potassium hydroxide (KOH) solution is used as the electrolyte. The test using electrolytes (KOH) revealed that the electrode's specific capacitance was 74.7 Fg <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> , the highest value discovered. However, using organic electrolytes would have produced better results that can be used as a guide for future advancements. The influence of activation temperature on the porous characteristics of prepared AC was investigated utilizing surface area and pore size analyses. The morphological characteristics of synthesized AC were analyzed through scanning electron microscopy (SEM) and Energy Dispersive X-Ray Analysis (EDX). Symmetric SC electrodes fabricated is analyzed in a two-electrode system applying standard electrochemical characterization methods using the potentiostat. Symmetric SC electrodes fabricated are analyzed in a two-electrode system applying standard electrochemical characterization methods using the potentiostat.

Contribution of modified P-enriched biochar on pH buffering capacity of acidic soil

Biochar can directly hold cations in soil because of the negative charge that exists on its surfaces. Besides, improving soil cation exchange capacity, the negative charges on biochar surfaces can buffer acid soil by protonation and deprotonation mechanisms. Moreover, biochar ameliorates soil acidity due to the presence of oxides, carbonates, and hydroxides of its basic cations (Ca, Na, K, and Mg). Both biochar surface functional group and basic cation concentrations can be altered by modification with chemical agents which can affect its soil pH buffering capacity. However, the impact of modified biochar application on soil pH buffering capacity is still scanty. This study investigated the pH buffering capacity of acidic soil amended with three P-enriched modified Douglas fir biochars and compared this buffering capacity to amendment with untreated Douglas fir biochar. These three P-enriched biochars, were prepared by treating Douglas fir biochar (DFB), respectively, with: 1) anhydrous calcium chloride (CaCl2) and potassium phosphate monobasic (KH2PO4), 2) calcium carbonate (CaCO3) and diammonium phosphate {(NH4)2HPO4} and 3) an aqueous solution of magnesium sulfate (MgSO4), potassium hydroxide (KOH) and potassium phosphate monobasic (KH2PO4). The three P-enriched biochars were designated as CCPP, CAPP and MSPP, respectively. The soil pH buffering abilities were largely dependent on the added biochar's alkalinity and ash contents. The residual soil CEC was highly correlated (r ≥ 0.9), with the soil buffering capacity. Both alkalinity and pH buffering capacity improved following the order CCAP > CCPP > MSPP > DFB, while residual soil CEC followed the order CAPP > MSPP > CCPP > DFB. The pH buffering capacity of the soil after amendments with 10% CAPP, CCPP MSPP and BFB rose by 84.8, 58.3, 3.0 and 2.5%, respectively. Whereas MSPP had higher concentrations of K+ and Mg2+, greater concentrations of Ca2+ were present in CCAP and CCPP than MSPP. So, Ca2+ concentrations in biochar exerts a greater influence on alkalinity and buffering capacity than Mg2+ and K+ because of 1) its smaller effective hydration radius and larger charge density. 2) calcium hydroxide has a greater water solubility than magnesium hydroxide providing more available base. Since pH buffering capacity depends on cation exchange sites, soil additives containing Ca2+ are prone to create greater impacts than Mg2+ and K+ additives.

PURIFICATION OF WATER SYSTEMS FROM URANIUM SALTS USING ACRYLONITRILE-STRUCTURED TRIPLE CO-OLIGOMERS OF 4-ISOPROPENIL-PHENOL, FORMALDEHYDE AND 4-(1-METHYL)-1-DIMETOXSI-PHOSPHORYLETHYL)PHENOL

The article presents the results of three-component condensation of 4-isopropenylphenol, formaldehyde and 4-(1-methyl)-1-dimethoxsiphosphorylethyl)phenol cooligomers, their structuring with acrylonitrile. In order to include the carboxyl group in the structure of the cross-linked copolymer, hydrolysis was carried out in the presence of an aqueous solution of potassium hydroxide. The process of sorption of uranyl ions from model aqueous systems by structured (crosslinked) with acrylonitrile and their product of hydrolyze. The structure of the cross-linked copolymer was confirmed by IR spectroscopy data. It has been established that the process of sorption of uranyl ions is significantly affected by the pH of the medium. The best results in the extraction of uranyl ions by the sorbent are achieved at pH 7–8 (at room temperature, the degree of their sorption is ~89–93%, and SCS is ~229–239 mg/g). It has been established that the process is completed within 24 hours, cross-linked co-oligomers can be reused after desorption of uranyl ions by mineral acids

Conversion of polyethylene terephthalate waste into high-yield porous carbon adsorbent via pyrolysis of dipotassium terephthalate

A method for conversion of polyethylene terephthalate (PET) waste into porous carbon material is proposed. The recycling of PET bottle waste includes the stages of low-temperature hydrolysis of the polymer and subsequent pyrolysis at 800 °C. To provide PET hydrolysis at ∼150 °C and atmospheric pressure, the polymer was pre-dissolved in dimethyl sulfoxide and then an aqueous solution of potassium hydroxide was added. The potassium terephthalate formed as a result of the alkaline hydrolysis of PET allows the carbon-containing precursor to be preserved for further activation to temperatures beyond 600 °C. The proposed method leads to the formation of a porous carbon material, increasing the yield of carbon residue to 25 wt%, which is higher compared to the yield of carbon residue in the direct pyrolysis of PET. The obtained porous carbon is characterized by graphite-like structure and specific surface area of ∼1100 m2 g−1. It has been shown that PET-derived carbon material can be used to remove pollutants from aqueous media. The adsorption properties of the carbon material were demonstrated by adsorption of methylene blue from an aqueous solution. The capacity of the carbon material was found to be 443 mg g−1.

A New Force Field for OH- for Computing Thermodynamic and Transport Properties of H2 and O2 in Aqueous NaOH and KOH Solutions.

The thermophysical properties of aqueous electrolyte solutions are of interest for applications such as water electrolyzers and fuel cells. Molecular dynamics (MD) and continuous fractional component Monte Carlo (CFCMC) simulations are used to calculate densities, transport properties (i.e., self-diffusivities and dynamic viscosities), and solubilities of H2 and O2 in aqueous sodium and potassium hydroxide (NaOH and KOH) solutions for a wide electrolyte concentration range (0-8 mol/kg). Simulations are carried out for a temperature and pressure range of 298-353 K and 1-100 bar, respectively. The TIP4P/2005 water model is used in combination with a newly parametrized OH- force field for NaOH and KOH. The computed dynamic viscosities at 298 K for NaOH and KOH solutions are within 5% from the reported experimental data up to an electrolyte concentration of 6 mol/kg. For most of the thermodynamic conditions (especially at high concentrations, pressures, and temperatures) experimental data are largely lacking. We present an extensive collection of new data and engineering equations for H2 and O2 self-diffusivities and solubilities in NaOH and KOH solutions, which can be used for process design and optimization of efficient alkaline electrolyzers and fuel cells.

Carbon catalysts from pine cones – Synthesis and testing of their activities

The work presents research on the synthesis of carbon catalysts from pine cones and their application in the oxidation of α-pinene. The preparation of carbon catalysts involved chemical activation with an aqueous potassium hydroxide solution and carbonization of the obtained precursor. The pine cones carbonization was performed for 1 h at the temperatures range from 700° to 1000°C in an inert gas atmosphere (N2). Characterizations of the activated carbons were performed with the following instrumental analyses: XRD, SEM, and XPS. No solvent was used in the oxidation studies, and molecular oxygen was the oxidizing agent. The effects of three parameters – temperature, amount of the carbon catalyst, and reaction time – on the values of conversion of α-pinene, as well as the product selectivities, were investigated. It was shown that it is most advantageous to perform the oxidation of α-pinene at 100 °C for 1 h with the PC_850 catalyst (so-named for the temperature of its carbonization process, 850 °C), whose content in the reaction mixture is 0.5 wt%. Under these conditions, the conversion of α-pinene amounted to 41 mol%. Moreover, the selectivities of the three main products were: α-pinene oxide (28 mol%), verbenol (16 mol%), and verbenone (13 mol%). In addition to these products, other valuable compounds, such as campholenic aldehyde, pinocarveol, myrtenal, myrtenol, carveol, carvone, and pinanediol were also produced.

Highly dispersed platinum on LaNi nanoparticles/nanoporous carbon for highly efficient electrocatalyic hydrogen evolution

Herein, we provide a two-step method to synthetize a cost-effective Pt1.5La1.5Ni12/NPC (NPC = nanoporous carbon) multimetallic electrocatalyst with a novel nanostructure of ultralow Pt decorated LaNi alloy nanoparticles for the hydrogen evolution reaction-HER in 1.0 M aqueous potassium hydroxide (KOH) solution. The catalytic performance of Pt1.5La1.5Ni12/NPC for the HER outperforms than Pt2La1Ni12/NPC, Pt1La2Ni12/NPC, Pt1.5La13.5/NPC, Pt1.5Ni13.5/NPC, La3Ni12/NPC and commercial Pt/C, and Pt1.5La1.5Ni12/NPC requires ultralow overpotential of 20 mV@10 mA cm−2, 132 mV@100 mA cm−2. It is due to the synergy (electron) effect among Pt-, La- and Ni-related species (electron from Pt to La and Ni), thus changing the electronic structure of the Pt-, Ni- and La-related species. The incorporation of La and Ni could facilitate the formation of OHads and Hads by water dissociation and weaken the bonding strength of Pt-Hads. The Pt1.5La1.5Ni12/NPC catalyst also shows outstanding stability during the HER process.