Neutral Reaction Research Articles

Alginic acid derivatives/DOPO modified epoxy resins: Excellent flame retardancy, mechanical properties, chemical resistance

An alginic acid derivative AA@MEL with flame retardant effect in both gas and condensed phases was synthesized by the neutralization reaction of alginic acid (AA) and melamine (MEL). Modified EP obtained the UL-94 V-0 rating and limiting oxygen index (LOI) of 33.8 % when the total addition of AA@MEL and 9,10-dihydro-9-oxa-10-phosphophenanthrene-10-oxide (DOPO) in the epoxy resin was only 4 wt% and the phosphorus content was only 0.29 %. Compared with pure EP, the total heat release (THR) and total smoke production (TSP) of flame-retardant EP were reduced by 42 % and 60 %, respectively, and the quality of the char residue was improved by forming higher graphitization layer. The flame retardancy mechanism was proposed through the pyrolysis products analyses and the characterization of the condensed phase. Meanwhile, the appropriate amount of AA@MEL/DOPO can enhance the tensile property, flexural property and impact strength of EP materials. It was closely related to the -COOH/-OH in AA@MEL and the P-H bond and rigid structure of DOPO. In addition, the modified EP has good chemical resistance, which ensures long-lasting flame retardant and mechanical properties. The AA@MEL/DOPO system exhibits low cost, low loading, high flame-retardant efficiency and environmental friendliness for industrial needs, which is promising for industrial applications.

Imaging the Ion-Molecule Reaction Dynamics of O- + CD4.

While neutral reactions involved in methane oxidation have been intensively studied, much less information is known about the reaction dynamics of the oxygen radical anion with methane. Here, we study the scattering dynamics of this anion-molecule reaction using crossed-beam velocity map imaging with deuterated methane. Differential scattering cross sections for the deuterium abstraction channel have been determined at relative collision energies between 0.2 and 1.5 eV and ab initio calculations of the important stationary points along the reaction pathway have been performed. At lower collision energies, direct backscattering and indirect complex-mediated reaction dynamics are observed, whereas at higher energies, sideways deuterium stripping dominates the reaction. Above 0.7 eV collision energy, a suppressed cross section is observed at low product ion velocities, which is likely caused by the endoergic pathway of combined deuteron/deuterium transfer, forming heavy water. The measured product internal energy is attributed mainly to the low-lying deformation and out-of-plane bending vibrations of the methyl radical product. The results are compared with a previous crossed-beam result for the reaction of oxygen anions with nondeuterated ̧methane and with the related neutral-neutral reactions, showing similar dynamics and qualitative agreement.

Renewable ammonium chloride-induced calcium leaching of gold and copper tailings and selective preparation of vaterite CaCO3 by CO2 mineralization

This study introduced a high-value green processing solution for copper tailings to prepare high-purity vaterite from gold-copper tailings. The active reaction components were determined through Gibbs free energy calculations. The study discusses the impact of different experimental parameters on the leaching rate of Ca2+ and the degree of mineralization in gold-copper tailings, and then considers the influence of different dispersants on improving the stability of vaterite. The results show that the optimal leaching efficiency of Ca2+ in the NH4Cl solution is 75%, and the optimal mineralization efficiency is 87%. Under appropriate mineralization conditions, vaterite CaCO3 with d50 < 12 μm, a purity of 98%, and a whiteness of 98.7% can be prepared. The precipitated vaterite is affected by the pH swing method connected with the neutralization reaction. The presence of excess NH3 and supersaturated CO2 are necessary for the formation of vaterite-type CaCO3. Morphological analysis results show that dispersants such as polyacrylamide and sodium tripolyphosphate can improve the dispersibility of vaterite, preventing agglomeration and enabling its stable existence in aqueous solutions. Nanoparticle aggregation and crystal growth are two possible mechanisms for the formation of vaterite. The leaching-mineralization cycle technology using NH4Cl as the leaching solution meets the requirements for CO2 removal and alkaline industrial waste residue treatment, while avoiding the significant consumption of chemical reagents in traditional mineralization. This method provides a pathway for producing vaterite using copper tailings and has a broad market prospect.

Facile synthesis of a novel organic salt containing DOPO and pyrimidine as a reactive additive for high‐efficiency flame retarding epoxy resin

AbstractA novel organic salt containing DOPO and pyrimidine (AD) was successfully synthesized through a simple acid–base neutralization reaction. The salt was used as a reactive flame retardant for epoxy resin. Non‐isothermal DSC tests disclosed that the epoxy resin displayed a lower temperature of onset curing and exothermic peak in the presence of AD. By using only 3 wt% AD, the epoxy resin achieved a UL‐94 V‐0 rating and a limited oxygen index value of 27.4%, revealing the high flame‐retardant efficiency of AD. AD inhibited the release of heat and smoke. The analysis of the flame‐retardant mode of action indicated that AD was able to impede combustion not only by the dilution and quenching effects in the gas phase but also by the charring effect in the condensed phase. During UL‐94 testing, 3 wt% AD gave the epoxy resin good flame retardancy due to the charring and blowing‐out effects formed by adding AD. The blowing‐out effect was that the release of strong airflows suppressed or even blew out the flame based on the dilution and quenching effects of phosphorous‐containing radicals and numerous non‐combustible gases produced by the degradation of AD and epoxy resin matrix. Additionally, the incorporation of AD slightly increased the glass transition temperature and the tensile and flexural strengths of the epoxy resin. This study provided a meaningful attempt to improve the flame retardance of epoxy resin by introducing a reactive pyrimidine‐organophosphonic acid salt.

Adaptation of Fildes Peninsula Lakes (King George Island, East Antarctica) to climate change and anthropogenic impacts

The load on the Antarctic oases has been recently increasing, with intensive research carried out by various countries and ecological tourism developing. This leads to an increase in the impact on the aquatic ecosystems of the lakes and streams in addition to the warming climate and glacier melting. This paper presents findings from a study of the Fildes Peninsula (King George Island) lakes’ aquatic ecosystems in the summer period of January–February 2020. In addition to results of hydrological and hydrochemical studies, the paper provides data from measurements of the self-cleaning ability of representative oasis lakes, as well as greenhouse gas fluxes from the lakes surface. The water level of the streams decreased 5 times over the summer season, and the water discharge — 10 times. The streams flowing from the glacier have the fullest water. The lakes have a neutral reaction, sometimes weakly alkaline; they are well aerated: the average value of dissolved oxygen in water is 85 %, occasionally supersaturation of up to 137% was observed. The concentration of nutrients in the water has amplitudes that are considerable for Antarctic oases lakes. A significant correlation can only be observed between nitrates and phosphates, and also between the water turbidity and the nutrients’ concentration. Maximum turbidity is observed in lakes with abundant content of bacterial mats. Most of the lakes have hydrochemical type II sodium chloride waters. The assessment of the lake self-cleaning ability using the ratio of destruction and organic matter production showed the general ability of ecosystems to cope with external (natural) pressures on ecosystems, but not in all cases. Eutrophication of the lakes and stream valleys is also noted. Carbon dioxide (CO2) absorption was observed in most of the streams and lakes, in some of them — methane (CH4) absorption as well. However, CH4 is generally emitted from the surface of the lakes. The largest values are recorded for small lakes located on glacial moraines and in places where ornithosoils are present. The agreement of the findings from the hydroecological studies of the Fildes peninsula lakes with those presented earlier by other authors makes it possible to conclude that there is a certain resistance of the lakes to climatic changes, but one can already talk about a significant anthropogenic impact on the freshwater oasis ecosystems.

Early properties of magnesium phosphate cement repairing material used in slab track

Magnesium phosphate cement (MPC) is a high-performance repairing material suitable for the interfacial disease of slab track. In this study, the early properties of MPC were optimized using central composite design (CCD) approach based on response surface methodology (RSM). Three factors with five levels and three responses were considered. The significance of the factors and their interactions were verified by using analysis of variance (ANOVA). The result show that the mass ratio of water-to-binder (W/b) affects fluidity, while the mass ratio of magnesia-to-phosphate (M/P) and borax-to-magnesia (B/M) impact the setting time of MPC. Higher W/b results in higher fluidity, while an increase in M/P reduces the setting time by increasing the neutralization reaction. Borax addition retards the reaction, prolonging the setting time. The three factors significantly affect the early compressive strength of MPC. At M/P = 3.5, the interweaving of MgO and K-struvite (MKP) forms a dense network structure, enhancing the strength. Borax and W/b interact to affect compressive strength, with borax retarding MKP crystal growth and higher W/b reducing compactness. Combined with microscopic property test, the strength generation mechanism of MPC with optimized mixing ratio was revealed, And the feasibility of field application of MPC was verified by strength test.

New hydroxylammonium-based protic ionic liquids: Influence of cation and anion structure on thermal, viscosity and conductive properties

In the research work, new protic ionic liquids (Pr-ILs) were synthesized by an acid-base neutralization reaction. The influence of IL chemical structure (i.e. anion and cation nature) on the thermal behavior, viscosity and ionic conductivity was evaluated. To confirm the chemical structure of synthesized Pr-ILs, nuclear magnetic resonance (1H and 19F) and Fourier transform infrared spectroscopy analyses were performed. Thermal analysis demonstrated that the influence of anion nature on the IL thermal stability was more pronounced than that of cation. The ionic liquids with trifluoromethanesulfonate anion showed the highest thermal stability (Tdeg ∼ 410–420 °C) as compared with other studied anions (i.e. phosphate and acetate anions). The trifluoromethanesulfonate-based Pr-ILs also demonstrated high ionic conductivity – between ∼58 and ∼64 mS·cm−1 at 150 °C and non-humid conditions. Despite the fact that phosphate-based Pr-ILs were more thermally stable (Tdeg ∼ 250–280 °C) than acetate-based ones (Tdeg ∼ 215 °C), acetate-based Pr-ILs revealed a higher ionic conductivity (∼15–19 mS·cm−1 at 80 °C) than phosphate-based Pr-ILs (∼0.2–1 and ∼0.4–2 mS·cm−1 at 80 and 120 °C, respectively). The obtained results confirm that the synthesized Pr-ILs are promising candidates for using them in electrochemical applications, namely, electrodialysis and fuel cells.

Sentiment Classification of Post-Earthquake Consumer Brand Hate on Social Media Using Machine Learning Techniques

The widespread use of social media allows consumers to evaluate brands and to get into a direct interaction with brands and other followers of the same brands. After the devastating earthquake on February 6th, 2023, in ten provinces in Turkey a social media brand hatred was observed on two global brands Netflix and Starbucks. Brands were accused of not showing the necessary sensitivity and empathy towards the affected and the brand devotees. The objective of this study is to examine and classify brand hatred in online consumer-generated content using supervised machine learning methods. While the construct of brand hate has been extensively investigated in the discipline of marketing using different data collection methodologies, this is one of the first attempts to use machine learning methods for the analysis of the phenomenon. Unlike classic polarization, the labeling process was associated with the size of brand hatred; 0 denotes neutral reactions, -1 negative emotional reactions, and -2 negative relationship reactions. Support Vector Machines (SVM) was identified as the most successful algorithm for the explanation of the phenomenon.

LC-MS/MS determination of pyocyanin-N-acetyl cysteine adduct: application for understanding Pseudomonas aeruginosa virulence factor neutralization.

Combating Pseudomonas aeruginosa infection is challenging. It secretes pyocyanin (PCN) pigment that contributes to its virulence. Neutralizing PCN via reaction with thiol-containing compounds may represent a potential therapeutic option. This study investigates the neutralization reaction between PCN and N-acetyl cysteine (NAC) for bacterial inhibition and explores its mechanism of action. The neutralization adduct (PCN-NAC) was synthesized by reacting the purified PCN and NAC. The adduct was analyzed and its structure was elucidated. LC-MS/MS method was developed for the determination of PCN-NAC in P. aeruginosa cultures post-treatment with NAC (0-5 mg/mL). The corresponding anti-bacterial potential was estimated and compared to nanoparticles (NPs) alone and under stress conditions. In silico studies were performed to support explaining the mechanism of action. Results revealed that PCN-NAC was exclusively detected in NAC-treated cultures in a concentration-dependent manner. PCN-NAC concentration (230-915 µg/mL) was directly proportional to the reduction in the bacterial viable count (28.3% ± 7.1-87.5% ± 5.9) and outperformed all tested NPs, where chitosan NPs induced 56.9% ± 7.9 inhibition, followed by zinc NPs (49.4% ± 0.9) and gold NPs (17.8% ± 7.5) even post-exposure to different stress conditions. A concomitant reduction in PCN concentration was detected. In silico studies revealed possible interactions between key bacterial proteins and PCN-NAC rather than the NAC itself. These results pose NAC as a potential choice for the management of P. aeruginosa infection, where it neutralizes PCN via the formation of PCN-NAC adduct.

Ion migration mechanism of electrochemical water softening in dual-chamber reactors and their performance for real circulating cooling water

Electrochemical water softening studies often use ion exchange membrane (IEM) reactors. However, their practical application is limited because of inevitable cathodic scaling. To overcome this challenge, one necessary approach is to understand the ion migration mechanism in the typical IEM reactor. In this study, we used operando visualization to reveal that the divider such as IEM or nylon nets was essential to confine the neutralization reaction between H+ and OH−. Ca2+ and Mg2+ may transfer from the anode chamber through the divider into the cathode chamber via electromigration. Using mesh electrodes instead of plate electrodes, the total hardness removal in the cathode chamber and anode chamber was 94.2% and 92.5%, respectively. The high removal rate was attributed to H2 microbubbles produced by cathodic water electrolysis, which drove OH− ions diffusion into solution and sequentially strengthened the nucleation of scale crystals in solution rather than on the cathode surface. On the basis of the above ion migration mechanism, the revolutionized reactor with mesh electrode module and nylon-net divider exhibited good performance in softening real circulating cooling water, and the total hardness removal exceeded 93.1% during 30 h running. These results open new horizons for improving the practicability of electrochemical water softening.

3D-printed open-source sensor flow cells for microfluidic temperature, electrical conductivity, and pH value determination

Due to the miniaturization of equipment for flow chemistry and microprocess engineering, low-cost sensors and analytical devices are becoming increasingly important for automated inline process control and monitoring. The combination of 3D printing technology and open-source lab automation facilitates the creation of a microfluidic toolbox containing tailored actuators and sensors for flow chemistry, enabling a flexible and adaptable design and efficient processing and control based on the measured data. This contribution presents a set of 3D-printed microfluidic sensor flow cells for inline measurement of temperature, electrical conductivity (EC), and pH value, while compensating for the temperature dependence of EC and pH. The tailored sensor flow cells were tested using model reactions in a single-phase capillary flow system. They have an accuracy comparable to reference sensors in batch measurements. The sensor data can be used to monitor the reaction progress (conversion), determine the kinetic data (activation energy, pre-exponential factors) of saponification reactions, and identify titration characteristics (equivalence and isoelectric points) of neutralization reactions. Hence, the 3D-printed microfluidic sensor flow cells offer an attractive alternative to commercial analytical flow devices for open-source and low-cost lab automation.Graphical abstract

The Development and Characterization of Novel Ionic Liquids Based on Mono- and Dicarboxylates with Meglumine for Drug Solubilizers and Skin Permeation Enhancers.

In this study, we synthesized a family of novel ionic liquids (ILs) with meglumine (MGM) as cations and tartaric acid (TA), azelaic acid (AA), geranic acid (GA), and capric acid (CPA) as anions, using pharmaceutical additives via simple acid-base neutralization reactions. The successful synthesis was validated by attenuated total reflection-Fourier transform infrared (ATR-FTIR) and powder X-ray diffraction (PXRD). Thermal analysis using differential scanning calorimetry confirmed the glass transition temperature of MGM-ILs to be within the range of -43.4 °C--13.8 °C. We investigated the solubilization of 15 drugs with varying pKa and partition coefficient (log P) values using these ILs and performed a comparative analysis. Furthermore, we present MGM-IL as a new skin permeation enhancer for the drug model flurbiprofen (FRP). We confirmed that AA/MGM-IL improves the skin permeation of FRP through hairless mouse skin. Moreover, AA/MGM-IL enhanced drug skin permeability by affecting keratin rather than stratum corneum lipids, as confirmed by ATR-FTIR. To conclude, MGM-ILs exhibited potential as drug solubilizer and skin permeation enhancers of drugs.

Catalyst-free, one-pot synthesis of N,N-di(α-amino aryl ketones) from aryl glyoxals and aryl amines in presence of guanidine as a source of nitrogen

Three-component reaction between aryl glyoxals, aryl amines, and guanidine afforded N,N-di (α-amino aryl ketone) derivatives. This method include two C–N bonds formation in a one-pot and single synthetic step in neutral and simple reaction conditions. All reactions were conducted in EtOH as solvent at reflux conditions without using any catalyst, and the stable products were obtained in high yields. The structures of all products were proved by 1H and 13C NMR, IR spectral and elemental analysis data.

Benzyl alcohol promoted electrocatalytic reduction of carbon dioxide and C2 production by Cu2O/Cu

Oxide-derived copper (OD-Cu)-based materials containing Cuδ+ (0 < δ ≤ 1) have been considered as promising electrocatalysts for electrochemical CO2 reduction reaction (ECO2RR) to produce valuable C2 products, which, however, suffer from poor stability, mainly due to the inevitable reduction of Cuδ+. We report here that the benzyl alcohol (BA) introduced in catholyte presents a markedly positive effect on the durability and C2 selectivity enhancement of ECO2RR when OD-Cu-based material is adopted as cathode electrocatalyst. The critical evidence of ECO2RR intermediates has been provided by in situ Raman and FTIR spectroscopy, which reveals the surface mechanisms of BA-assisted ECO2RR over OD-Cu catalysts. On the one hand, the introduction of BA increases the CO2 supply for ECO2RR by slowing down its neutralizing reaction, which results in the increased intermediate species coverage on the catalytic surface therefore the delayed self-reduction of Cuδ+; On the other hand, the interaction between BA and the intermediate species *CO during ECO2RR brings an enhanced selectivity of C2 products (FE C2 = 85.5 % at −1.38 V vs RHE). Besides, an energy-savings and economic electrolyzer can be achieved by coupling anodic BA oxidation reaction to benzoic acid and ECO2RR to C2 products with much lowered cell voltages.

Study on the onset mechanism of bio-blister degradation of polyolefin by diatom attachment in seawater

It is essential to develop a mechanism for lowering the molecular weight of polyolefins to achieve biodegradation in seawater. In this study, a polypropylene/polylactic acid blend sample was first subjected to photodegradation pretreatment, and it was confirmed that in pure water, the acid generated promotes the polypropylene degradation (autoxidation), while in alkaline seawater, the promotion was inhibited by a neutralization reaction. In the autoxidation of polyolefins in alkaline seawater, aqueous Cl− was also the inhibitor. However, we found that autoxidation could be initiated even in seawater by lowering the pH and using dissociation of ClOH (called blister degradation). The blister degradation mechanism enabled autoxidation, even in seawater, by taking advantage of the ability of diatoms to secrete transparent exopolymer particles (TEP) to prevent direct contact between the surface layer of polyolefins and alkaline seawater. We named blister degradation in seawater with diatoms as bio-blister degradation and confirmed its manifestation using linear low-density polyethylene (LLDPE)/starch samples by SEM, IR, DSC and GPC analysis.

Low Palladium‐Loading HY Zeolite Catalyzed Hydrolysis of Hydrosilanes to Silanols and Alkoxysilanes

AbstractA low palladium‐loading heterogeneous catalyst has been developed for the hydrolysis of hydrosilanes to silanols and alkoxysilanes under mild and neutral reaction conditions with broad substrate scope. After five recycling runs, this low palladium‐loading catalyst keeps good activity for this transformation.

Teaching Acid-Base Fundamentals and Introducing pH using Butterfly Pea Flower Tea.

Stimulating interest in science at an early age is important for STEM education. This work details an educational activity utilizing the anthocyanins found in the butterfly pea flower (Clitoria ternatea). This activity was developed for use in official classroom settings, online, and/or at-home with parental or educator guidance. Primary and high school students aged 7 to 14 performed a straightforward extraction of anthocyanin pH indicators from Clitoria ternatea with hot water. Students were able to use this indicator and its vast range of colors to compare the acidity and basicity of different household solutions. Most responses recorded show that students used reasoning from the indicator and a subsequent chemical reaction to correctly differentiate acids from bases and compare their strengths. Overall, this activity's application of non-toxic and easily accessible indicators from the butterfly pea flower assisted in introducing young students to various concepts in acid-base chemistry, including acid/base strength and pH, solute dissolution, neutralization reactions, and qualitative analysis.

Enhancing Recovery Yield of Vegetable Oil Methyl Ester for Bioresin Production: A Comparison Study Using Acid Neutralization

Vegetable oil methyl ester has promising properties for bio-based resin production due to its higher degree of unsaturation. The initial low methyl ester yield from corn oil compared to soybean and canola oils requires further investigation of the influence of neutralization at the end of the transesterification reaction. To evaluate the neutralization effect with HCl, corn, canola, and soybean oil were transesterified using NaOH at 60 °C with a 6:1 methanol–oil ratio. This research also investigated the effect of reaction times (0.5–1.5 h) with varying neutralization levels (0–100%) on the corn oil methyl ester yield. The yield of corn, canola, and soybean methyl ester was increased significantly by 16–25% through neutralization, indicating the positive impact of neutralization. The corn oil methyl ester yield ranged from 45 to 79% across different neutralization levels and reaction times. With 25% neutralization, the yield increased by 20%. On the other hand, the yield reduced by 18–24% over time when there was no neutralization. A statistical model was developed where the yield varied significantly with the acid amount, reaction time, and their interactions. The quality of the corn methyl ester was found to be within the limits of standard pure methyl ester. Overall, the effect of neutralization showed promise in increasing the yield of quality methyl ester from commercial corn oil.

Standardization of the Japanese National Standard, Equine Botulinum Antitoxin Type A, and Factors Affecting Standardization.

Equine botulinum antitoxin is one of the most popular countermeasures for human botulism. The unitage of the antitoxin product is defined according to national minimum requirement or pharmacopoeia in each country by referring to national standard antitoxins for four types (A, B, E, and F). With the expected depletion of the national standard antitoxins, replacement national standard antitoxins are produced and standardized through collaboration of the National Control Laboratory and other participants, including manufacturer(s). Therefore, Japanese National Standard Botulinum Antitoxin Type A, Equine, was replaced according to the results of a collaborative study involving the National Institute of Infectious Diseases and KM Biologics Co., Ltd. The unitage of the replacement material was determined through mouse neutralization tests, which involved toxin-antitoxin mixture injection at pH 7.0. Potency value of 440 units/vial was obtained. However, the Japanese Minimum Requirement for Biological Products was revised, and the neutralization reactions were repeated at pH 6.0, for which considerably different potency value (656 units/vial) and survival profile of mice were obtained. In September 2021, the replacement material, Japanese National Standard Botulinum Antitoxin Type A, Equine, lot 2, was established with potency value of 656 Units/vial. The impact of pH-dependent change in potency on antitoxin quality control is discussed.

Synthesis of Hydroxylammonium Nitrate and Its Decomposition over Metal Oxide/Honeycomb Catalysts

The objectives of this study were to prepare a high-purity hydroxylammonium nitrate (HAN) solution and evaluate the performance of various types of metal oxide/honeycomb catalysts during the catalytic decomposition of the HAN solution. Hydroxylammonium nitrate was prepared via a neutralization reaction of hydroxylamine and nitric acid. FT-IR was used to analyze the chemical composition, chemical structure, and functional groups of the HAN. The aqueous HAN solution obtained from pH 7.06 showed the highest concentration of HAN of 60% and a density of 1.39 g/mL. The concentration of HAN solution that could be obtained when the solvent was evaporated to the maximum level could not exceed 80%. In this study, catalysts were prepared using a honeycomb structure made of cordierite (5SiO2-2MgO-2Al2O3) as a support, with Mn, Co, Cu, Pt, or Ir impregnated as active metals. The pore structure of the metal oxide/honeycomb catalysts did not significantly depend on the type of metal loaded. The Cu/honeycomb catalyst showed the strongest effect of lowering the decomposition onset temperature in the decomposition of the HAN solution likely due to the intrinsic activity of the Cu metal being superior to that of the other metals. It was confirmed that the effect of the catalyst on the decomposition mechanism of the aqueous HAN solution was negligible. Through a repetitive cycle of HAN decomposition, it was confirmed that the Cu/honeycomb catalyst could be recovered and reused as a catalyst for the decomposition of an aqueous HAN solution.