Acidic Aqueous Solution Research Articles

DECOMPOSITION OF PHOSPHORUS-CONTAINING COMPOUNDS IN AQUEOUS AND POLYSACCHARIDE SOLUTIONS OF ORGANIC ACIDS

The purpose was to study the patterns of dissolution (solubilization) of phosphorus-containing minerals in aqueous and polysaccharide solutions of organic acids in order to model the mechanism of mineral destruction by soil bacteria synthesizing organic acids and exopolysaccharides. Methods. Model, laboratory-analytical, microbiological, statistical. Results. The destructive effect of organic acids on minerals is manifested both in aqueous and polysaccharide solutions. The introduction of bacterial polysaccharide into an aqueous solution of acids increases the decomposition of phosphorus-containing minerals by 1.34̶ 4.96 times. The influence of the chemical structure of acid molecules on the intensity of mineral decomposition is mainly manifested in the presence of bacterial polysaccharide, while in an aqueous solution the effectiveness of acid action depends on the nature of the mineral being destroyed. To the maximum degree, polysaccharide increases the destruction of minerals in a solution of citric acid: molten magnesium phosphate ̶ 2.55 times, thermophosphate ̶ 2.11 times, phosphate flour ̶ 4.96 times. Decomposition of phosphorus compounds in solutions of ascorbic and oxalic acids enhances bacterial polysaccharide to a lesser extent than in citric acid solution. Modeling the destruction of phosphorus-containing minerals under non-sterile conditions (soil conditions) made it possible to establish that organic acids under non-sterile conditions are subject to consumption by soil microbiota, especially ascorbic and citric acids, and to a lesser extent - succinic. Aqueous solutions of organic acids after 18 hours of incubation in non-sterile conditions lose their leaching activity by 1.06 ̶12.1 times. The introduction of a polysaccharide into aqueous solutions of acids makes it possible to avoid their rapid consumption by microorganisms, because of which the efficiency of mineral leaching under non-sterile conditions decreasшes by only 5–20% compared to sterile ones. Conclusions. The introduction of a bacterial polysaccharide into a solution of organic acids enables the latter to be transferred to a sorbed state, as a result of which their susceptibility to consumption by microorganisms is sharply reduced. Thus, polysaccharide-forming bacteria not only destroy minerals more intensively than microorganisms synthesizing only low-molecular-weight metabolites, but also synthesize a more stable and long-term functioning leaching complex in the soil.

Chemical facets of environment-friendly corrosion impediment of low-carbon steel in aqueous solutions of inorganic mineral acid

Chemical facets of environment-friendly corrosion impediment of low-carbon steel in aqueous solutions of inorganic mineral acid

Thermal-gas-chemical method for oil production intensification in low-temperature reservoirs

A method is proposed for developing an oil deposit based on low-temperature oil oxidation as a result of initiating an exothermic reaction and subsequent injection of oxygen-containing gas into the reservoir. In the proposed method, which includes successive injection of aqueous solutions of potassium salt and sulfuric acid into the well, light oil or gas condensate is injected into the deposit before injection of the aqueous acid solution. Further, after injection of an aqueous solution of sulfuric acid into the formation, air is pumped with further pushing with water. In the method, a 16% aqueous solution of potassium dichromate is used as an aqueous solution of potassium salt. The application of the proposed technology led to an increase in the temperature in the reservoir above 200 °C and an increase in the displacement efficiency up to 19.7%. Keywords: thermal chemical treatment; production stimulation; low-temperature reservoir; enhanced oil recovery; low temperature oxidation; oil displacement.

Factors influencing on the formation of dimethyl disulfide and dimethyl trisulfide in model systems

The generations of dimethyl disulfide (DMDS) and dimethyl trisulfide (DMTS) in a binary or ternary model system including lipids, free amino acids and Maillard reaction products (MRPs) were studied. Various factors affecting the formation of DMDS and DMTS indicated that cysteine (Cys) and Cys MRPs could effectively decrease not only the concentrations of methionine (Met), DMDS and DMTS, but also the pH level. Rapid drops in pH limited the formation of DMDS and DMTS during Met thermal degradation. Quantitative analyses of DMDS and DMTS at acidic aqueous solutions revealed that the mixtures of MRPs derived from Cys and xylose (Xyl) had the best inhibition effect on the formation of DMDS and DMTS. The low level of DMDS and DMTS and the increasing level of furfuryl methyl sulfide and 2-thiophenecarboxaldehyde during storage indicated that MRPs derived from Cys and Xyl could effectively not only decrease the concertation of DMDS and DMTS, but also promote the development of thiophene and sulfur substituted furan. Thus, this study implied that MRPs derived from Cys/Xyl could be applied as effective substances to control the formation of DMDS and DMTS and improve the production of volatile compounds with meat-like aroma.

Green synthesis of 3,4-disubstituted isoxazol-5(4H)-one using Gluconic acid aqueous solution as an efficient recyclable medium.

Green synthesis of 3,4-disubstituted isoxazol-5(4H)-one using Gluconic acid aqueous solution as an efficient recyclable medium.

ISOLATION, CHEMICAL AND SPATIAL CHARACTERIZATION OF ACIDIC POLYSACCHARIDES FROM SOME PLANTS OF SIBERIAN FLORA WITH IMMUNOTROPIC ACTIVITY

Plant polysaccharides have a wide range of biological activity, including an immunotropic effect, the degree and magnitude of which depends on the composition and tertiary structure of the macromolecule. Acidic polysaccharides (APS) were isolated by extraction with an acidic aqueous solution (pH=3) and characterized From the rhizomes of Acorus calamus L., the aerial part of Centaurea pseudomaculosa Dobrocz., the herb Conium maculatum L., and the leaves of Betula pendula Roth. The content of total carbohydrates was determined for all samples (>90%), uronic acids (24.56–53.70%) and a small amount of impurity substances (protein and nucleic acids 0.81–1.02% and 0.016–0.035%, respectively); molecular weight distribution (Mn, Mw). Structural features were studied using physicochemical and instrumental methods, such as UV and IR spectroscopy, reaction with Congo red, and scanning electron microscopy. The polysaccharides of Acorus calamus, Conium maculatum, and Betula pendula have a triple-helical conformation and bulky ultrastructure; the polysaccharides of Centaurea pseudomaculosa are characterized by the absence of a triple-helical conformation and an amorphous ultrastructure.

A bio-based reprocessable and degradable polybenzoxazine with acetal structures

In this work, a bio-based reprocessable and degradable polybenzoxazine with acetal structures was designed and prepared. A diphenol containing acetal structures (DVEA) was reacted with stearylamine and paraformaldehyde to obtain a benzoxazine monomer (DVEA-s). The curing behavior of DVEA-s was investigated using differential scanning calorimetry and in-situ Fourier transform infrared spectroscopy, and the curing kinetics of DVEA-s were also studied. Due to the thermal exchange of acetal structures, the obtained polybenzoxazine (PDVEA-s) exhibited quick stress relaxation. Mechanically crushed PDVEA-s could be reprocessed by hot-pressing at 120 °C for 10 min. Furthermore, the degradation properties of PDVEA-s under different conditions were studied. The results showed that PDVEA-s could be completely degraded in acidic tetrahydrofuran aqueous solution at 50 °C in 4 min.

Liquid–Liquid Equilibria of Butyric Acid, Water, and Methyl Isobutyl Ketone with the Aid of Biological Buffer as a Green Auxiliary Agent

Biological buffer has a significant impact on aqueous organic phase equilibria in extraction processes. This study investigated the effect of biological buffer on the efficacy of butyric acid extraction from aqueous solution utilizing methyl isobutyl ketone (MIBK) as the extraction solvent. The liquid–liquid equilibria (LLE) of quaternary systems of methyl isobutyl ketone (MIBK) + butyric acid + water + biological buffer MOPS [3-(N)-morpholino propane sulfonic acid], HEPES (2-(4-(2-hydroxyethyl)-1-piperazinyl)ethanesulfonic acid), or EPPS (4-(2-hydroxyethyl)-1-piperazine propanesulfonic acid) were determined at temperature T = 303.15 K (30 °C) and P = 0.1 MPa (atmospheric pressure). The addition of EPPS to the butyric acid aqueous solution resulted in superior extraction efficacy compared to the other biological buffers, as determined by experimental data. Generally, the extraction performance was in the order EPPS > MOPS > HEPES, which represented the buffering-out strength as well. The non-random two-liquid (NRTL) and UNIversal QUAsi Chemical (UNIQUAC) models fit well with the actual LLE data of the quaternary systems. The σ-profile analysis was also evaluated in this study. Additionally, a potential process flow sheet using biological buffer and MIBK solvent was suggested for removing butyric acid from its aqueous solution.

Room-Temperature Growth of Morphoplastic Scandium Nanowires through Coordination-Induced Self-Assembly for White-Light-Driven Photocatalytic Degradation of Rhodamine

Photoactive nanowires play an important role on the photoelectric-related applications; however, the in situ large-scale growth of photoactive nanowires on the arbitrary substrate still faces a great challenge. Herein, for the first time, we develop a facile coordination-induced self-assembly strategy for preparing the nanowires with high photoactivity through keeping a high concentration of Sc(NO3)3 and tartaric acid (TA) aqueous solution at room temperature. Surprisingly, the nanowires can grow directionally along the direction of water flow on any substrate due to the growth mechanism driven by water molecules, showing that the proposed nanowires are morphoplastic depending on the direction of liquid flow. The formation of nanowires has been proved to be attributed to the synergistic effect of water molecule-involved hydrogen bonding between hydroxyl groups of TA ligands as well as the multi-coordination of Sc3+ ions. Meanwhile, the prepared nanowires are highly photoactive, showing a strong photooxidation ability toward rhodamine 6G dyes, with a degradation efficiency of about 95.8% within 40 min. This finding introduces a coordination growth mechanism of nanowires, which not only provides a great possibility for large-scale and low-cost synthesis of photoactive nanowires with morphoplastic features but also shows a good application prospect in water cleaning by the photocatalysis technique.

Thermodynamic properties of evaporative crystallization of high-salt wastewater

High-salt wastewater requires a lot of energy during the evaporative crystallization process, and this energy consumption increases with the width of the metastable zone. In order to reduce the width of the metastable zone, this paper investigates the influence of cooling rate, pH, stirring rate and iron ion addition on the width of the metastable zone of sulphate in the CLT acidic aqueous solution system. The saturation and supersaturation at the onset of nucleation are determined by the conductivity method. The results show that the best crystal promotion is achieved at a cooling rate of 0.2 °C/min, a pH value of 3 and a stirring rate of 200 r/min. The iron ions, which promotes the crystallization but reduces the purity, should be replaced by crystal seeds. This study can provide reference for improving efficiency and saving energy during the evaporative crystallization of high-salt wastewater.

Ionic liquid promoted extraction of gold(III) from electronic waste: a modeling study

ABSTRACT Being an expensive metal, the large-scale requirement of gold in the ever-growing market of electronics increases the overall cost of manufacturing. Hence, recycling gold from electronic waste mitigates the demand and subsequently bounds the price of electronic goods. However, the extraction of gold from electronic waste poses a severe hazard to the environment. Because of tuneable and fascinating properties, ionic liquids (ILs) have emerged as state-of-the-art solvents to extract gold from electronic waste. Herein, the modeling of IL-assisted liquid-liquid-extraction incorporating UNIQUAC extended Pitzer–Debye–Hückel* (PDH*) thermodynamic model has been used for the extraction process of gold from an aqueous acidic solution. The long-range, weak electrostatic interactions present in ionic liquids are adequately represented by the extended PDH* model. The model parameters are obtained from the polarizable continuum medium (PCM) calculation, conductor-like screening model for real solvent (COSMO-RS), and genetic algorithm formulation. Altogether, 11 hydrophobic ILs consisting of 9 imidazolium, 1 pyrrolidinium, and 1 ammonium class with 51 tie line data points are considered for the modeling. The estimated root mean square deviation of 0.002–0.99% over 51 tie lines reveals the goodness of the fitting. The projected percentage extraction efficiency lies in the range of 98.5% to 99.3%.

The degradation behaviors of optical cellulose triacetate films in alkali/acid solutions

Abstract In this research, the degradation behaviors of ramie-based cellulose triacetate (CTA) films in alkali or acid solutions at room temperature were assessed. Moreover, the attenuated total reflection infrared (ATR-IR), physicochemical properties testing, scanning electron microscope (SEM), and thermogravimetric analysis/differential scanning calorimeter (TG/DSC) were employed to evaluate the detailed degradation process of the CTA films, which were treated by alkali or acidic aqueous solutions. The research results demonstrated that the dominant reaction of CTA films in NaOH solution with various concentrations is deacetylation. Intriguingly, the degradation behaviors of CTA films in HCl depend on the concentration of acid. The CTA films were almost immune to HCl with the concentration less than 1 mol L−1. However, films were degraded directly when the concentration of acid was higher than 1 mol L−1. This study provides a theoretical basis and further understanding for the treatment of dumped CTA films at room temperature.

Valorization of Boehmeria nivea stalk towards multipurpose fractionation: furfural, pulp, and phenolic monomers

BackgroundAs one of the most abundant bioresource in nature, the value-added utilization of lignocellulosic biomass is limited due to its inherent stubbornness. Pretreatment is a necessary step to break down the recalcitrance of cell walls and achieve an efficient separation of three main components (cellulose, hemicelluloses, and lignin).ResultsIn this study, hemicelluloses and lignin in Boehmeria nivea stalks were selectively extracted with a recyclable acid hydrotrope, an aqueous solution of P-toluenesulfonic acid (p-TsOH). 79.86% of hemicelluloses and 90.24% of lignin were removed under a mild pretreatment condition, C80T80t20, (acid concentration of 80 wt%, pretreatment temperature and time of 80 °C and 20 min, respectively). After ultrasonic treatment for 10 s, the residual cellulose-rich solid was directly converted into pulp. Subsequently, the latter was utilized to produce paper via mixing with softwood pulp. The prepared handsheets with a pulp addition of 15 wt% displayed higher tear strength (8.31 mN m2/g) and tensile strength (8.03 Nm/g) than that of pure softwood pulp. What’s more, the hydrolysates of hemicelluloses and the extracted lignin were transformed to furfural and phenolic monomers with yields of 54.67% and 65.3%, respectively.ConclusionsThe lignocellulosic biomass, Boehmeria nivea stalks, were valorized to pulp, furfural, and phenolic monomers, successfully. And a potential solution of comprehensive utilization of Boehmeria nivea stalks was provided in this paper.Graphical

Highly conductive, durable, washable, and scalable composite yarn for multifunctional wearable electronic applications

Fiber-based electronics with excellent flexibility and functionality have recently attracted widespread attention in the field of wearable devices. However, it remains challenging to develop conductive fibers with high electrical conductivity, efficient fabrication yield, and excellent durability simultaneously. Herein, a scalable continuous capillary dip-coating strategy was proposed to prepare washable carbon nanotube (CNT)/waterborne polyurethane (WPU) composite yarns. By the optimized two-step dip-coating and heat-stretching procedure, we achieve yarns with a high loading of 60 wt% CNTs and electrical conductivity of over 3 × 103 S/m. The excellent interfacial interaction between the polyvinyl pyrrolidone (PVP) in conductive layer and WPU in protect layer enables the ultra-high durability and stability of yarns. Consequently, conductive yarn showed high reliability upon microenvironment change of wearable interfaces in various temperature, humidity, aqueous acid, and alkaline solutions. The response to bending, friction, and washing in practical application is also marginal, which enable conductive yarn to construct conveniently wearable electronic devices for various applications through braiding technology. This work provides a simple route for the development of fiber-based electronics and promises satisfactory application in wearable flexible fabric devices.

Improving the Mechanical Properties and Tribological Behavior of Sulfobetaine Polyurethane Based on Hydrophobic Chains to Be Applied as Artificial Meniscus.

In the context of meniscus reconstruction in knee joints, current bulk biomaterials fail to meet the clinical demands for both excellent mechanical strength and low coefficient of friction. In this research, zwitterionic polyurethanes (PUs) with varying sulfobetaine (SB) groups were synthesized as the potential materials for artificial meniscus to investigate the relationship between the structures of SB groups and the performances of PUs. Under the saturation condition of 3 mg/mL hyaluronic acid aqueous solution, PU with long-alkyl chains and SB groups (PU-hSB4) exhibited a good tensile modulus (111.5 MPa) because the hydrophobic interaction of carbon chains was able to maintain the ordered aggregations of hard segment domains. Interestingly, hydrophobic chains in the molecular chain could also improve the tribological performance of PU-hSB4 instead of resulting from the surface roughness of samples, the components of lubricants, and the counterface of samples. A thicker and relatively stable hydration layer of noncrystal water was formed on the surface of PU-hSB4, which exhibited superior resistance to external forces compared to other PUs. Even if the hydration layer was damaged, PU-hSB4 was able to resist the compression of cartilage due to its high surface modulus, thus maintaining a similar and stable coefficient of friction (0.15-0.16) to native meniscus (0.18) and excellent wear resistance. In addition, the low cytotoxicity of PU-hSB4 further demonstrated its great potential to be applied in artificial meniscus instead.

An Alkanethiol-Surfactant Bilayer To Prevent Shape Conversion of Anisotropic Silver Nanoparticles and Probe Their Formation Mechanisms.

Anisotropic nanoparticles can be synthesized under kinetic control but may undergo subsequent shape changes due to atomic reorganization. Furthermore, their synthesis involves rapid steps, which are challenging to monitor in situ. Here, we show how a nanoemulsion of alkanethiols with an ethoxylated surfactant, easily prepared and metastable for months, can simultaneously prevent shape reorganization and arrest reaction kinetics. We illustrate this generic method on the silver nanoplates synthesized in concentrated acetic acid aqueous solutions, in which rapid shape reorganization occurs. We show that there exists an optimum thiol concentration corresponding to full coverage of all silver surface atoms, which can be simply calculated from particle dimensions. Furthermore, we demonstrate that arresting nanoparticle formation can be achieved within milliseconds using a tandem rapid mixers scheme in a continuous flow setup, allowing ex situ monitoring of the reaction.

A facile bioorthogonal chemistry-based reversible to irreversible strategy to surmount the dilemma between injectability and stability of hyaluronic acid hydrogels

Injectable and stable hydrogels have great promise for clinical applications. Fine-tuning the injectability and the stability of the hydrogels at different stages has been challenging due to the limited number of coupling reactions. A distinct “reversible to irreversible” concept using a thiazolidine-based bioorthogonal reaction between 1,2-aminothiols and aldehydes in physiological conditions to surmount the dilemma between injectability and stability is presented for the first time. Upon mixing aqueous solutions of aldehyde-functionalized hyaluronic acid (SA-HA) and cysteine-capped ethylenediamine (DI-Cys), SA-HA/DI-Cys hydrogels formed through reversible hemithioacetal crosslinking within 2 min. The reversible kinetic intermediate facilitated thiol-triggered gel-to-sol transition, shear-thinning and injectability of the SA-HA/DI-Cys hydrogel but then converted to the irreversible thermodynamic network after injection, thereby permitting the resulting gel with improved stability. As compared to the Schiff base hydrogels, the hydrogels generated from this simple, yet effective concept awarded improved protection to the embedded mesenchymal stem cells and fibroblast during injection, retained the cells homogeneously within the gel, and allowed them further proliferation in vitro and in vivo. There is potential for the proposed approach of “reversible to irreversible” based on thiazolidine chemistry to be applied as a general coupling technique for developing injectable and stable hydrogels for biomedical applications.

Leaching of rare earth elements from coal ash using low molecular weight organocarboxylic acids: Complexation overview and kinetic evaluation

AbstractThe study of thermodynamics and kinetics of leaching rare earth elements (REEs) is a fundamental aspect in understanding the mechanism behind the leaching process. Leaching of REEs from coal ash with aqueous solution of organocarboxylic acid is a heterogeneous fluid‐particle system. In the present study, the leaching mechanisms of these three potential organocarboxylic acids, tartaric acid, lactic acid, and citric acid were examined over a range of temperature (30–90°C) at various leaching durations. The kinetic data thus obtained were found to follow deviation from the conventional shrinking core model (SCM). A mixed mechanism model was deduced to be the optimum fit to the data with high precision (R2 > 0.95) and desired graphical linearity with closer interception to the origin. Aluminosilicate matrix remained unaltered after acid treatment which is the unchanged core concluded as from the kinetic mechanism. Morphological analysis using Scanning Electron Microscope (SEM) and particle size determinations were suggestive of significant reduction in grain size post leaching with organocarboxylic acids, tartaric acid being the most effective of all.

A high adhesion co-assembly based on myclobutanil and tannic acid for sustainable plant disease management.

Pesticides are irreplaceable inputs for protecting crops from pests and improving crop yield and quality. Self-assembly nanotechnology is a promising strategy by which to develop novel nano-formulations for pesticides. Nano-formulations improve the effective utilization of pesticides and reduce risks to the environment because of their eco-friendly preparation, high drug loading, and desirable physicochemical properties. Here, to enhance the utilization efficiency of myclobutanil (MYC) and develop a novel nano-formulation, carrier-free co-assembled nanoparticles (MT NPs) based on MYC and tannic acid (TA) were prepared by noncovalent molecular interactions using a green preparation process without any additives. The results showed that the prepared spherical nanoparticles had good stability in neutral and acidic aqueous solutions, low surface tension (40.53 mN m-1 ), high rainfastness, and good maximum retention values on plant leaves. Release of active ingredients from MT NPs could be regulated by altering the molar ratio of subassemblies in the co-assembly and the pH of the environment. Antifungal experiments demonstrated that MT NPs had better activities against Alternaria alternata and Fusarium graminearum [half-maximal effective concentration (EC50 ) = 6.40 and 77.08 mg/L] compared with free MYC (EC50 = 11.46 and 124.82 mg/L), TA (EC50 = 251.19 and 503.81 mg/L), and an MYC + TA mixture (EC50 = 9.62 and 136.21 mg/L). These results suggested that MYC and TA incorporated in the co-assembled nanoparticles had a synergistic antifungal activity. The results of a genotoxicity assessment indicated that MT NPs could reduce the genotoxicity of MYC to plant cells. Co-assembled MT NPs with synergistic antifungal activity have outstanding potential for the management of plant diseases. © 2023 Society of Chemical Industry.

Hydroxy sulfonic acid catalyzed hydrolysis of cellulose

Development of efficient catalytic methods for the hydrolysis of cellulose is a major research challenge in sustainable biofuel and polymer areas. In this study five hydroxy sulfonic acids were studied as simple model compounds for cellulase enzyme for the hydrolysis of cellulose. The catalytic activities were measured by analysis of total reducing sugar (TRS) yields produced in a series of reactions carried out at 150–190 °C using 0.050 M aqueous hydroxy sulfonic acid solutions. The highest catalytic activity was observed with isethionic acid, producing 62.7% TRS yield at 180 °C after 4 hr. In the second phase of the work, Density Functional Theory (DFT) calculations were used to study the interactions between hydroxy sulfonic acids and cellulose model compound D-cellobiose to supplement the experimental results. The D-cellobiose – hydroxy sulfonic binding energies and the distance between glycosidic oxygen and -SO3H acidic H were evaluated and the -SO3H to glycosidic oxygen distance was identified as the more important parameter co-related to the catalytic activity. The isethionic acid with highest cellulose hydrolysis activity showed the shortest -SO3H to glycosidic oxygen distance of 1.744 Å.