Hydrochloric Research Articles

Toward Polymeric Room Temperature Acid Generators.

Although a variety of acid-generating molecules have been developed, the formation of toxic byproducts and the need for light-activation or temperatures that may be incompatible with physiological conditions leave room for the optimization of biocompatible acid-generators. Herein, we report 4-hydroxybenzyl chloride derivatives that generate hydrochloric acid via hydrolysis at the benzylic position at room temperature in the absence of light. Utilizing the acetal protected 4-hydroxybenzyl chloride scaffold, we access a myriad of compounds that generate acid at different rates.

Synthesis and cyclic voltammetric studies of azo dye compounds derived from 1,5-dihydroxynaphthalene and their application as corrosion inhibitors for carbon steel in hydrochloric acid solution

New bis-azo dyes derived from 1,5-dihydroxynaphthalene were synthesized and characterized by elemental analysis, Fourier-transform infrared (FTIR) and proton nuclear magnetic resonance spectroscopy (1H NMR). These compounds were examined using differential pulse polarography (DPP) and cyclic voltammetry (CV) in Britton-Robinson buffer solutions with pH values ranging from 2 to 12. When the two NN centers of the examined azo compounds were cleaved to form the amine group, the bis-azo group was reduced with the loss of eight electrons, resulting in an irreversible diffusion-controlled cathodic peak. The reduction mechanism was postulated in view of the data obtained was found to be H+, e, e, H+. The application of these azo compounds as corrosion inhibitors for carbon steel in hydrochloric acid solution was investigated and the inhibition efficiency was found to be increasing with both time and concentration, reaching 97 % after 24 hours in the presence of 10−3 M for the three azo compounds. The Langmuir adsorption isotherm indicates that the suppression of corrosion is caused by the inhibitor molecules donating electrons to the empty d-orbitals of the surface of the carbon steel (chemical adsorption), as the calculated Gibbs free energy (∆Gads) is found to be around −40 kJ/mol. The influence of temperature on the parameters of corrosion was examined, and the thermodynamic parameters of corrosion were computed and examined. The results showed that increasing temperature causes increasing of the inhibition efficiency of the tested bis-azo dyes. The order of inhibition efficiency followed their donating affinity which increases in the order p-OCH3 > p-CH3 > m-CH3. Also, the results showed that these compounds causes decrease in entropy, enthalpy and activation energy due to their chemical interaction with the metal surface.

A Novel Strategy to Construct Metal–Organic Frameworks‐Based Memristor with Enhanced Proton Conduction

The limited conductivity of metal‐organic frameworks (MOFs) poses a significant challenge to their application in the domain of memristors. The proton conduction capabilities of MOFs can be improved through the incorporation of guest molecules. Herein, hydrogen protons are introduced into MIL‐53 (Al) via acid leaching, which not only enhances the proton conductivity of MIL‐53 (Al) but also contributes to its superior resistance switching behavior. The results indicate that untreated MIL‐53 (Al) exhibits negligible resistance switching behavior; however, following hydrochloric acid leaching, it demonstrates excellent retention (103 cycles), longtime durability (103 s), and a favorable ON/OFF ratio (≈25) under bias conditions. Furthermore, under suitable pulse stimulation, the MIL‐53 (Al)‐based memristor successfully emulates biological synaptic behaviors, including excitatory postsynaptic current and paired pulse facilitation. This research presents a novel approach for enhancing the resistive switching performance of MOF‐based memristors.

Adsorption efficiency and photocatalytic activity of silver sulphide-activated carbon (Ag2S-AC) composites

BackgroundThis study investigates the adsorption efficiency and photocatalytic activity of silver sulphide-activated carbon (Ag2S-AC) composites derived from ground coffee waste (GCW). MethodsIn this work, GCW was preceding to carbonized at 500 ± 2°C for hours and formed biochar. Then, GCW was subjected to activation using hydrochloric acid (HCl), phosphoric acid (H3PO4) and potassium hydroxide (KOH). The mixture was left to soak for 24 h at room temperature, followed by carbonization at 350 and 500˚C. In the meantime, the silver sulphide (Ag2S) was synthesized by using an ion exchange method. Sodium sulphide (Na2S) was used as sulphur source and mixed with silver nitrate (AgNO3) and sodium citrate (NaCit) for two hours, then dried in oven at 50 ± 2°C for 10 h. Next, the carbonized AC was subsequently combined with synthesized silver sulphide, resulting in the creation of Ag2S-activated carbon composites that functioned both as adsorbent and photocatalyst. Their capabilities as adsorbents and photocatalyst were studied by using copper ions (Cu2+) and methylene blue (MB) solution. Significance findingsBased on results, GCW and all the prepared activated carbons are in the amorphous phase, except for the Ag2S-AC composites, where the Ag2S peak reflection can be observed from the X-ray diffraction (XRD) pattern. GCW shows rough and dense surface morphology. The AC shows different pore sizes and structures depending on the chemical activators used, where AC-KOH shows the largest pore size (165.31 μm). The existence of micropores can be observed in all the activated carbon samples. For the adsorption of Cu2+, all samples show more than 99 % of the removal efficiency. While for photocatalytic testing, the Ag2S-H3PO4 sample shows the highest degradation rate (97.7 %) of MB solutions.

Decapsulation of artemia cysts (Artemia sp.) using different versions of sodium hypochlorite solutions (NaOCL)

The article describes the technology of Artemia decapsulation, its features and external factors affecting the efficiency of hatching with subsequent use as a feed composition. Artemia nauplii and its eggs, due to their high nutritional value and high digestibility in the digestive tract, are widely used in growing sturgeon larvae and other fish species. Artemia decapsulation is one of the most important factors in the transition of fish larvae to active feeding, in this regard, it is very important to select the optimal decapsulation conditions, the composition of chemical reagents, temperature and light conditions. The decapsulation process is a chemical process of removing the hard shell that surrounds the Artemia embryo. The procedure involves hydration, during which the outer shell is removed, can be carried out with a number of solutions: sodium hydroxide, sodium carbonate, sodium hypochlorite, hydrochloric acid. However, they all show different availability and efficiency in decapsulation. The most common is the use of sodium hypochlorite solutions, but they do not show stable results, since the process of decapsulation and hatching of nauplii from cysts depends on many factors. The aim of the work was to study the methods of decapsulation of Artemia eggs for their use as a starter feed when transferring to active feeding and feeding of sturgeon larvae. As a result of the experiments, a technology for incubating Artemia eggs in accessible conditions without the use of professional equipment was developed. Cysts are incubated in aerated Weiss apparatuses, under constant illumination, in a volume of 7 liters of water, at a concentration of: NaCl — 30%, artemia cysts 3 g/l, water temperature — 28 °С. The cysts are decapsulated without soaking, with 2.5% NaOCl solution with a total volume of 300 ml (21 g of dry cysts + 150 ml of water + 150 ml of NaOCl) for 4–5 minutes.

Leather Waste Hydrolysation, Carbonization, and Microbial Treatment for Nitrogen Recovery by Ryegrass Cultivation.

Leather waste contains up to 10% nitrogen (N); thus, combustion or gasification only for the energy recovery would not be rational, if safety standards are met. On the other hand, the chromium (Cr) content exceeding 5% in half of the waste stream (w/w) is too significant to be applied in agriculture. In this work, four acid hydrolysates from leather waste shavings, both wet-white free of Cr and wet-blue with Cr, were used: two with a mixture of acids and supplemented with Cu, Mn, and Zn, and the other two as semi-products from collagen extraction using hydrochloric acid. Additionally wet-green leather waste shavings, e.g., impregnated with olive extract, were used followed by the two treatments: amendment with a biochar from "wet white" leather waste shavings and amendment with this biochar incubated with the commercial phosphorus stimulating microbial consortia BactoFos. They were applied as organic nitrogen-based fertilizers in a glasshouse experiment, consisting of 4-5 subsequent harvests every 30 days, under spring-autumn conditions in northern Poland. Biochar-amended wet-greens provided the highest nitrogen use efficiencies, exceeding 100% after 4 months of growth (for 20 kg N/ha) and varying from 17% to 37% in particular months. This is backed up by another parameter (relative agronomic effectiveness) that for these materials exceeded 150% for a single month and in total was around 33%. Biochar amendments significantly increased agronomic parameters for wet-greens, and their microbial treatment enhanced them even further. Recycling this type of waste can replace inorganic fertilizers, reducing greenhouse gas emissions and carbon footprint.

An advanced separation method for the acquisition of 212Pb/212Bi from natural thorium

212Pb/212Bi hold significant potential for targeted cancer therapy; however, their supply remains severely limited. The extraction of 212Pb/212Bi from natural thorium is expected to fundamentally address this issue. This study proposes and verifies a new, efficient and low-cost method for separating 212Pb/212Bi from natural 232Th by investigating the separation behavior and mechanism of a silica-supported anion exchange resin (SiPyR-N4) toward multiple types of metal cations in hydrochloric solution. The experimental results demonstrated that SiPyR-N4 was successfully prepared with a uniform shape, porous structure, and containing quaternary amines. SiPyR-N4 showed extremely high selectivity for Pb2+ and Bi3+, but no affinity for Th4+, La3+, and Ba2+. The adsorption speed was more than six times as fast as traditional resins, providing significant advantages in the separation of short-lived nuclides. The hot separation experiment suggested that 212Pb and 212Bi were successfully isolated from natural 232Th by using natural thorium as the raw material, and the long-lived nuclides were removed completely. The selective separation mechanism was attributed to Pb2+ and Bi3+ forming anionic complexes in the hydrochloric acid medium, while Th4+, Ra2+, and Ac3+ did not form such complexes. Pb2+ and Bi3+ were bound to the active sites via chloride bridges, with [PbCl3]− and [BiCl6]3− serving as the main adsorbed species. This study is the first to report the direct and selective separation of 212Pb and 212Bi from 232Th decay chains using non-crown ether materials, and it provides an excellent material candidate for the separation of short-lived nuclides, showing significant application potential in the future.

225Aс/213Bi generator for direct synthesis of 213Bi-labeled bioconjugates

Background213Bi is a short-lived radionuclide currently trialed for alpha therapy of various oncological diseases. A serious obstacle to the wide medical use is decay losses of 213Bi during a conventional synthesis of radiopharmaceuticals. In this work, we aimed to develop a two-column 225Aс/213Bi generator providing the accumulation of 213Bi separately from the parent 225Ac via continuous circular separation and decay of intermediate 221Fr. When attaining the transient equilibrium, 213Bi could be promptly extracted from the generator with an appropriate complexing agent, including chelator-protein bioconjugates. MethodsSorption behavior of Bi(III) ions onto the cross-linked dextran gel Sephadex G-25 was studied from solutions of hydrochloric and nitric acid, and from sodium chloride, sodium acetate and DTPA solutions. A bifunctional chelating agent p-SCN-Bn-DTPA was conjugated to an antibody Nimotuzumab specific to the epidermal growth factor receptor, and the procedure of 207,213Bi-DTPA-Nimotuzumab synthesis in the dextran gel medium was developed. The parameters of 225Aс/213Bi generator system were evaluated. ResultsThe weight distribution ratios of Bi(III) adsorbed onto the Sephadex G-25 gel were obtained. Up to 85 % of 213Bi was accumulated in the second Sephadex-filled column of 225Aс/213Bi generator after four-hour circulation of 0.15 M NaCl (pH 5.5) solution. Having passed the solution of DTPA-Nimotuzumab bioconjugate through the second column, a fraction of 213Bi-DTPA-Nimotuzumab radioimmunoconjugate was produced with the radiochemical yield of 64 % ± 3 % (n = 6). High radionuclidic and radiochemical purity of product was achieved. ConclusionsThe circulating 225Aс/213Bi generator provides a 213Bi-labeled bioconjugate as a final product. While a conventional synthesis route including generator milking, bioconjugate labeling and size-exclusion purification takes >20 min, the duration of 213Bi-DTPA-Nimotuzumab production by the method proposed in this work is reduced to 6–8 min.

Evaluating novel piperazine derivatives as aluminum corrosion inhibitor: a computational study

Purpose The aim of this study is to evaluate the corrosion inhibitory properties of three piperazine derivatives – Ethyl 5-(piperazine-1-yl) benzofuran-2-carboxylate (EPBC), 5-[4–(1-tert-butoxyethenyl) piperazin-1-yl]-1-benzofuran-2-carboxamide (BBPC) and Tert-butyl-4–(2-(ethoxycarbonyl)benzofuran-5-yl)-piperazine-1-carboxylate (TBPC) – on Al surfaces in the presence of hydrochloric acid (HCl). The research uses density functional theory (DFT) and molecular dynamics simulations to explore the effectiveness of these derivatives as corrosion inhibitors and to understand their adsorption behavior at the molecular level. Design/methodology/approach This study uses a computational approach using DFT at various levels (B3LYP/6–31+G(d,p), B3LYP/6–311+G(d,p), WB97XD/DGDZVP) to calculate essential quantum chemical parameters such as energy gap (ΔE), ionization energy (I), absolute electronegativity (χ), electron affinity (E), dipole moment (µ), absolute softness (s), fraction of electron transferred (ΔN) and absolute hardness (η). The Fukui function and local softness indices are used to assess the sites for electrophilic and nucleophilic attacks on the inhibitors. Molecular dynamics simulations are performed to analyze the adsorption behavior of these derivatives on the Al (110) surface using the adsorption locator method. Theoretical methods like DFT provide quantum chemical parameters, explaining inhibitor reactivity, whereas molecular dynamics simulate adsorption behavior on Al (110), both supporting and correlating with experimental inhibition efficiency trends. Findings This study demonstrates that all three piperazine derivatives exhibit strong adsorption on the Al surface, with high adsorption energies, good solubility and low toxicity, making them effective corrosion inhibitors in acidic environments. Among the three, TBPC showed superior inhibitory performance, particularly in the presence of HCl, due to its optimal electronic properties and stable adsorption on the Al (1 1 0) surface. Originality/value This research contributes to the field by combining DFT calculations and molecular dynamic simulations to evaluate the corrosion inhibition potential of piperazine derivatives comprehensively. This work advances the understanding of the adsorption mechanisms of organic inhibitors on metal surfaces and offers a detailed quantum chemical and adsorption behavior analysis.

Particle-stabilized foams with fatty acid salts as stabilizers triggered by transition metal ions

Particle-stabilized foams have been becoming the focus on foaming field because of their excellent stability due to the high stiffness of interface membrane. However, the modification of particle surfaces to reach an appropriate wettability needs complicated process, resulting in accompanied inconvenient foaming-defoaming regulation. In this work, we reported a series of foams stabilized by insoluble particles generated from fatty acid anions with metal ions. Different hydrocarbon chains endowed the formed particles diverse wettability and different aggregation behaviors at the gas–liquid interface, e.g., different foamability and the formation of the “dry water”. The foams exhibited ultra-stable properties and were responsive to environmental acidity, thus possessing a smart foaming-defoaming transition tuned by pH. The combination ability of fatty acid anions with metal ions changed with the chain-length and the nature of metal ions, leading to a choice for the extraction or separation of some metal ions in a fast and simple way. This new aggregation behavior of fatty acid salts can be explored to expand the practical applications.

Structures of hexamethyl-[1,1′-biphenyl]-4,4′-diammonium salts

The crystal structures of nine hexamethyl-[1,1′-biphenyl]-4,4′-diammonium (HMB) salts are described: the iodide (2), triiodide (3), succinate (4), fumarate (5), tetravanadate (6), hydroterephthalate (7) and perylenetetracarboxylate (8), as well as pentamethyl-[1,1′-biphenyl]-4,4′-diammonium iodide (1) and the metal–organic framework sodium diacetylenedisalicylate–HMB (9). HMB carbonate (10) has been synthesized as an important intermediate for a promising anti-metal–organic framework (`anti-MOF'). All the described compounds are characterized by high solubility in water. The results suggest that, during crystallization, crystallohydrates are formed from water. Compounds 6 and 9 are characterized by the presence of a rigid framework; compound 6 has an open framework structure filled with water molecules. Synchronous thermal analyses of compounds 2, 4, 6, 7, 8 and 10 allowed the identification of similarities in the mechanisms of thermolysis. At about 80–180°C, the loss of crystallization water molecules occurs. Between 180 and 250°C, a methyl group (methyl cation) is split off from the quaternary ammonium salt to form tetramethylbenzidinium. In the case of the iodides and salts of organic acids, the second thermolysis product is the methyl ester of this acid (methyliodide, dimethyl carbonate), which easily evaporates. In the range 240–355°C, tetramethylbenzidinium evaporates without decomposition.

Functional and molecular characterization of millet associated probiotic bacteria

The lactic acid bacteria are one of the sustainable ways of food production. As the native lactic acid bacteria (LAB) easily manipulate the substrate, helps in production of health essential probiotics with enhancing the bioavailability of the substrate. Here also, in present study, the native LAB isolates isolated from the millets and characterize them for the functional analysis for the human health association. In the present study, fermented millet-associated lactic acid bacteria were screened and characterized for their probiotic potential, safety evaluation and antimicrobial activity. A total of 33 isolates were purified as lactic acid bacteria based on colony shape and biochemical assays. However, only 13 isolates were found to be catalase-negative. Among the 13 isolates, 5 isolates exhibited optimum growth at 6.5% and 9.5% of salt concentrations, pH of 4.5 to 8.5 and 17 °C to 40 °C of the temperature. The probiotic properties of the five isolates exhibited that the survival rates in acid and bile salt concentration ranged from 56.2 to 73.7% and 55.3 to 70.3%, respectively. Similarly, the surface hydrophobicity of the isolates was 41–75%. Antibiotic assay revealed that all five isolates were resistant to Amoxicillin, Cloxacillin, and Penicillin-V. Interestingly, all the isolates except ME26 displayed susceptibility towards Penicillin (2 units) and Tetracycline (10 µg). Further, the four isolates (ME25, ME26, ME9, and ME2) had more antifungal activity against Aspergillus flavus. However, only three, except ME1 and ME2, showed maximum antibacterial activity and produced more antimicrobial compounds compared to reference strain L. plantarum Pb3. The potential probiotic isolates were identified as Weisella cibaria ME9, Weisella cibaria ME26, and Weisella confusa ME25.

A Fluorescent Covalent Organic Cage for Ultrafast Detection of Picric Acid and HCl Vapor Sensing.

Covalent organic cages (COCs) have recently gained massive attention owing to their solution processability and structural flexibility. Herein, we report an amine-linked fluorescent COC (COC2) synthesized by adopting dynamic covalent imine chemistry followed by imine bond reduction and characterized with different spectroscopic techniques. The COC2 was utilized for highly sensitive and selective detection of picric acid at the nanomolar level. The fluorescence quenching efficiency of PA towards the COC2 is 98.6%, with a detection limit of 2.7 nM. PA sensing with the COC2, coated on a TLC plate and paper strip, exhibited an outstanding fluorescence quenching property. Furthermore, the COC2 unveiled solid-state acidochromism upon exposure to HCl acid fumes and was transferred back to the original form on exposure to NH3 vapours.

Preparation of High-Purity Nano-Iron Phosphate from Titanium-Extraction Tailings by Co-Leaching Synergetic Ultrasonic-Enhanced Precipitation Process.

The preparation of high-performance electrode materials from metallurgical solid waste is an effective strategy to address current energy and environmental challenges. This study utilizes a mixed acid leaching and ultrasound-assisted precipitation process to extract valuable metallic iron from titanium-extraction tailings (TET) to produce high-purity nano-FePO4 electrode material precursors with unique crystal structures. A leaching efficiency of 95.2% for Fe was attained by using the optimized process parameters, which included a mixed acid concentration of 4 mol/L, a liquid-to-solid ratio of 4:1, and a leaching temperature of 70 °C for 1 h. The optimal precipitation conditions were a pH of 2.0, a temperature of 60 °C, an aging time of 30 min, and a stirring speed of 600 rpm, resulting in FePO4 purity up to 99.6% and fine particle size. Thermodynamic calculations, combined with various characterizations, elucidated the leaching and precipitation mechanisms, highlighting the synergistic effect of phosphoric acid and hydrochloric acid in enhancing the leaching reaction. The thermogravimetric analysis indicated that the decomposition of residual ammonium chloride impurities requires calcination above 360 °C. This research not only provides new insights into the high-value, clean utilization of metallurgical solid waste but also supports sustainable resource recovery and environmental protection by transforming waste into valuable products.

The Efficient and Environmentally Friendly Chlorination of Arene, Alcohol, Halobenzene, and Peroxide Catalyzed by Fe-Ba Binary Oxides Using Hydrochloric Acid as Chlorine Source and Aqueous H2O2 as Oxidant.

A series of Fe-Ba mixed oxides, including a pure Fe-containing sample as a reference, have been synthesized via a sol-gel process using Fe3+ or Fe2+ salts and BaSO4 as raw materials, with Pluronic P123 serving as a template. These oxides have been thoroughly characterized and subsequently utilized as catalysts for the chlorination of various organic molecules. Commercial hydrochloric acid, known for its relative safety, and environmentally friendly aqueous hydrogen peroxide were employed as the chlorine source and oxidant, respectively. The pure Fe-containing catalyst displays excellent thermal stability between 600 and 800 °C and exhibited moderate to high conversions in the chlorination of toluene, benzene, and tert-butyl hydroperoxide, with remarkable ortho-selectivity in chlorination of toluene. The combination of Fe3+ salt with BaSO4 in the sol-gel process results in a Fe-Ba mixed oxide catalyst composed of BaO2, BaFe4O7, and Fe2O3, significantly enhancing the chlorination activity compared to that displayed by the pure Fe catalyst. Notably, the chlorination of tert-butyl hydroperoxide (TBHP) does not require additional oxidants such as H2O2, and involves both electrophilic substitution and nucleophilic addition. Notably, the chlorination of bromobenzene yields chlorobenzene as the sole product, a transformation that has not been previously reported. Overall, this catalytic chlorination system holds promise for advancing the chlorination industry and enhancing pharmaceutical production.

Extraction of pectin from powdered citrus peels using various acids: An analysis contrasting orange with lime

Pectin, a vital hydrocolloid, is widely utilized in food, medicine, and cosmetics for its gelling, thickening, and stabilizing properties. Although citrus peels are used for pectin production, there is a need to enhance extraction efficiency and identify the optimal methods for commercial use. This study aimed to optimize pectin extraction from orange peel powder (OPP) and lime peel powder (LPP) using different acids (0.05M HCl, H₂SO₄, HNO₃, and citric acid) under controlled conditions (80°C, pH 2.0) for 60 and 90 min. The highest pectin yield was achieved at 90 min, with sulfuric acid yielding 21.63% from OPP and citric acid producing 32.53% from LPP, confirmed by principal component analysis (PCA). The extracted pectin was analyzed for several key characteristics, including moisture content, ash content, equivalent weight, methoxyl content, anhydrouronic acid (AUA) content, and solubility in hot and cold water, and hot and cold alkali. Pectin from OPP exhibited higher moisture and ash levels than that from LPP. Specifically, OPP-derived pectin demonstrated 61.65% esterification, 7.29% methoxyl content, 67.19% AUA content, and an equivalent weight of 683.41 mg/mL. In contrast, pectin extracted from LPP showed 66.39% esterification, 7.73% methoxyl content, 66.09% AUA content, and a higher equivalent weight of 792.57 mg/mL. Both OPP and LPP yielded high-methoxyl pectin suitable for gelling applications. PCA revealed that pectin extracted from LPP had superior values for equivalent weight, methoxyl content, and esterification degree compared to OPP. Interestingly, AUA content negatively correlated with these properties, while other parameters were positively correlated. These findings indicate that using citric acid to extract pectin from lime peels could outperform current commercial methods, yielding high-methoxyl pectin with excellent gelling properties. This makes it especially valuable for industrial applications in the food, pharmaceutical, and cosmetic sectors.

Optimization for Corrosion Inhibition of Steel in Hydrochloric Acid by DHOT as a Novel Corrosion Inhibitor

Optimization for Corrosion Inhibition of Steel in Hydrochloric Acid by DHOT as a Novel Corrosion Inhibitor

Investigation on vapour–liquid equilibrium (VLE) solubility of CO2 in aqueous solutions of amino sugars

AbstractAmino sugars, which are candidate CO2‐capturing solvents, react reversibly with CO2, thereby setting up vapour–liquid equilibrium (VLE). Knowing equilibrium data is useful for designing gas–liquid contactors for CO2 absorption. In this work, VLE data for two amino sugars, glucosamine (GA) and N‐methyl‐D‐glucamine (NMG), was measured and reported at 303, 308, and 313 K using a high‐pressure VLE setup for the first time. The equilibrium CO2 partial pressure was high (up to 1500 kPa). The molarity of sugar in the aqueous solution was in the 0.5–1.25 M range. It was found that the CO2 loading capacity of NMG was much higher than that of GA. For instance, 1.25 M NMG loaded 1.066 mol/mol at 303 K and 1500 kPa CO2 partial pressure. Using regression, empirical equations were developed to predict VLE data for GA and NMG. To enable comparison, VLE trials were also performed using two amines, monoethanolamine (MEA) and 2‐amino‐2‐methyl‐1‐propanol (AMP), and an amino acid salt potassium glycinate (PG). It was found that CO2 solubility (α, mol/mol) in NMG was comparable to that in MEA and higher than that in PG. Besides, it was also found that CO2 was most soluble in AMP. The effect of promoter addition on the loading capacity at T = 308 K was studied too. The value of CO2 solubility in GA solution (1 M) at = 1450 kPa was α = 0.298 mol CO2/mol amino sugar. It improved to α = 0.46 mol/mol in GA/NMG (1/0.5 M) mixtures. Similarly, the CO2 solubility in NMG solution (0.75 M) at = 250 kPa was α = 0.76 mol CO2/mol amino sugar. It improved to 0.94 and 0.93 mol/mol in NMG/PZ and NMG/AMP (0.75/0.25 M) mixtures (here, PZ denotes piperazine). In this way, this work provided new and useful VLE data for individual and blended sugar solutions.

Metal-Exchanged Phosphomolybdic Acid Salts-Catalyzed Esterification of Levulinic Acid

We examined the effectiveness of metal-exchanged phosphomolybdic acid salts in converting levulinic acid, derived from biomass, into valuable products (alkyl levulinate). We prepared salts of phosphomolybdic acid using different metals (Fe3+, Al3+, Zn2+, Cu2+, Mn2+, Ni2+, and Co2+). The influence of metal cations on the conversion and selectivity of the reactions was assessed. We found that the salts prepared with iron and aluminum phosphomolybdate were the most effective catalysts for the esterification of levulinic acid with methanol, with the conversion and selectivity tending towards 100% after 6 h of reaction at a temperature of 323 K. The effect of catalyst loading and its recovery and reuse was evaluated; the results from the reaction using aluminum phosphomolybdate remained similar for four cycles of use. The influence of temperature on conversion and selectivity was investigated between 298 and 353 K. The reactivity of different alcohols with a carbon chain size of C1-C4 was assessed and conversions above 65% were obtained for all alcohols tested under the conditions evaluated, except for tert-butyl alcohol. These catalysts are a promising alternative to the traditional soluble and corrosive Brønsted acid catalysts. The superior performance of these catalysts was ascribed to the higher pH decline triggered by the hydrolysis of these metal cations.

Comparative enhancement of H+ and OH− treatment on electromagnetic interference shielding in aligned and compact Ti3C2Tx MXene film

Abstract The pressing demand for ultrathin and flexible shields to counter electromagnetic interference (EMI) has sparked interest in Ti3C2Tx MXene materials due to their exceptional electrical conductivity, tunable surface chemistry, and layered structure. However, pure Ti3C2Tx MXene films often lack the mechanical properties required for practical engineering applications, and traditional reinforcement methods tend to reduce electrical conductivity. This work demonstrates an effective strategy to enhance the alignment and densely packed layered structure of Ti3C2Tx MXene films by regulating the acidity and alkalinity of Ti3C2Tx MXene aqueous solutions. This approach simultaneously improves mechanical strength and electromagnetic interference shielding effectiveness (EMI SE). Compared with original Ti3C2Tx MXene films, MXene films modified with ammonia solution (NH3·H2O) via OH− show a significant improvement in tensile strength (27.7 ± 1.9 MPa). Meanwhile, MXene films treated with hydrochloric acid (HCl) via H+ reach an even higher tensile strength of 39 ± 1.5 MPa. Moreover, the EMI SE values of the treated MXene films increase significantly, each reaching 66.2 and 58.4 dB. The maximum improvements in EMI SE values for the acid- and alkali-treated samples are 17.9% and 4%, respectively. In conclusion, the simultaneous enhancement of mechanical strength and EMI shielding efficacy highlights the potential of acid- and alkali-treated Ti3C2Tx MXene films for applications in ultrathin and flexible EMI shielding materials. Graphical abstract