Weak Salts Research Articles

Ischemic stroke: focus on hyperuricemia

Uric acid is a weak organic acid with a molecular weight of 168.112 g/mol. Most uric acid at normal blood pH circulates as urates, negatively charged weak salts derived from uric acid. Being the end product of the process of purine catabolism, uric acid is excreted from the human body in urine until kidney function is impaired. Hyperuricemia may occur due to decreased excretion, increased production, or a combination of both mechanisms. Over the past decades, several studies in the adult population have attempted to establish the correlation between the risk of stroke and serum uric acid concentrations, and how these levels influence the patient's neurological outcome after stroke. Our review is devoted to the study of the mechanisms of normal purine metabolism, disorders of purine metabolism and pathogenetic mechanisms of the development of ischemic stroke in hyperuricemia.

Influence of weak acid salts and curing condition on supersulfated cement mortar

This study explores the impact of weak acid salt agents (citrate and tartrate) in the mixture and various curing conditions on the properties of supersulfated cement (SSC) mortar. Compressive strength tests were conducted on prism-shaped samples measuring 4 × 4 × 16 cm. A comprehensive analysis of the phase assemblage of hardened products was carried out using X-ray diffraction (XRD), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS). The results reveal the abundant formation of ettringite (E) and hydrotalcite (Ht) when weak acid salt agents are added, especially in chloride and sulfate-rich curing solutions, leading to a notable increase in compressive strength, up to 200% compared to the control sample. Furthermore, the study demonstrates a substantial improvement in early and overall strength under temperature-stimulated curing conditions, accelerating the hydration reaction of SSC. These findings provide deeper insights into the factors influencing SSC hardening and strength development, offering valuable information for enhancing the efficiency and utilization of SSC in the construction industry, aligning with the goals of sustainable development.

The influence of different kinds of weak acid salts on the macro-performance, micro-structure, and hydration mechanism of the supersulfated cement

Supersulfated cement (SSC), mainly composed of solid wastes, is a highly promising low-carbon binding material, however, the application of SSC is still limited due to inherent defects in terms of strength and durability. In this paper, the influence of addition of different weak acid salts on the micro-structure and macro-performance of SSC has been investigated, and a pH-based mechanism for regulating the hydration process of supersulfated cement is proposed. The experimental results show that sodium lactate and low content of sodium citrate both promote the formation of hydration products AFt and C–S–H gel, which is beneficial to the improvement of frost resistance and the retention of strength in SSC. Furthermore, it is found that the dynamic adjustment of the pH value in the pore solution during the hydration process is a necessary condition for high performances of supersulfated cement, which can be realized by the weak acid salts. The high pH value in the early stage of hydration should be present to ensure the rapid dissolution of slag and gypsum, while the pH must be decreased to a certain value as the reaction proceeds, for the purpose of the stable growth of AFt. The mechanism interpreted here may pave the way for the mix optimization and broader application of SSC.

O AMBIENTE ESTUARINO E A VARIAÇÃO DE pH: LIMITES NATURAIS E OBSERVAÇÃO EXPERIMENTAL DO EFEITO DA ACIDIFICAÇÃO SOBRE A BIODISPONIBILIDADE DE FÓSFORO

THE ESTUARINE ENVIRONMENT AND pH VARIATION: NATURAL LIMTS AND EXPERIMENTAL OBSERVATION OF THE ACIDIFICATION EFFECT ON PHOSPHORUS BIOAVAILABILITY. This study shows the variation of pH in the Cananéia-Iguape Estuarine-Lagoon Complex (CIELC). Data from 3 years (2019, 2021, 2022) were obtained in 17 points presenting the following ranges: temperature (14.88-27.05 ºC), pH (7.16-8.40) and DIP (0.20-11.28 µmol L-1) along a saline gradient (0.05-32.09) under different hydrodynamics, biogeochemical processes and anthropogenic influence. The pH buffering capacity due to the presence of weak acid salts in saline water (S ≥ 30) was associated to the lowest DIP, decreasing with low salinity values, confirming the direct correlation among salinity and pH. The highest temperatures in the winter of 2021, corroborated with the abnormal climate event in that year. An in vitro experiment showed results of the interaction of PID and sediments with different textures, with and without the presence of the benthic microbiota under a considerable decreasing of the pH (acidification) in relation to the natural condition of this environment. The P sediment flux characterized Iguape sector as a P sink with or without biota, Ararapira sector as a P source with biota and Cananéia, as P source without biota. The salt water buffered the pH and sediment buffered DIP both associated to the biogeochemical and hydrodynamic processes contribute to the homeostasis in the system.

Constant-potential molecular dynamics simulations of molten salt double layers for FLiBe and FLiNaK.

We report the results of constant-potential molecular dynamics simulations of the double layer interface between molten 2LiF-BeF2 (FLiBe) and 23LiF-6NaF-21KF (FLiNaK) fluoride mixtures and idealized solid electrodes. Employing methods similar to those used in studies of chloride double layers, we compute the structure and differential capacitance of molten fluoride electric double layers as a function of applied voltage. The role of molten salt structure is probed through comparisons between FLiBe and FLiNaK, which serve as models for strong and weak associate-forming salts, respectively. In FLiBe, screening involves changes in Be-F-Be angles and alignment of the oligomers parallel to the electrode, while in FLiNaK, the electric field is screened mainly by rearrangement of individual ions, predominantly the polarizable potassium cation.

Influence of Electroconvection on Chronopotentiograms of an Anion-Exchange Membrane in Solutions of Weak Polybasic Acid Salts.

Visualization of electroconvective (EC) vortices at the undulated surface of an AMX anion-exchange membrane (Astom, Osaka, Japan) was carried out in parallel with the measurement of chronopotentiograms. Weak polybasic acid salts, including 0.02 M solutions of tartaric (NaHT), phosphoric (NaH2PO4), and citric (NaH2Cit) acids salts, and NaCl were investigated. It was shown that, for a given current density normalized to the theoretical limiting current calculated by the Leveque equation (i/ilimtheor), EC vortex zone thickness, dEC, decreases in the order NaCl > NaHT > NaH2PO4 > NaH2Cit. This order is inverse to the increase in the intensity of proton generation in the membrane systems under study. The higher the intensity of proton generation, the lower the electroconvection. This is due to the fact that protons released into the depleted solution reduce the space charge density, which is the driver of EC. In all studied systems, a region in chronopotentiograms between the rapid growth of the potential drop and the attainment of its stationary values corresponds to the appearance of EC vortex clusters. The amplitude of the potential drop oscillations in the chronopotentiograms is proportional to the size of the observed vortex clusters.

A predictive model for salt nanoparticle formation using heterodimer stability calculations

Abstract. Acid–base clusters and stable salt formation are critical drivers of new particle formation events in the atmosphere. In this study, we explore salt heterodimer (a cluster of one acid and one base) stability as a function of gas-phase acidity, aqueous-phase acidity, heterodimer proton transference, vapor pressure, dipole moment and polarizability for salts comprised of sulfuric acid, methanesulfonic acid and nitric acid with nine bases. The best predictor of heterodimer stability was found to be gas-phase acidity. We then analyzed the relationship between heterodimer stability and J4×4, the theoretically predicted formation rate of a four-acid, four-base cluster, for sulfuric acid salts over a range of monomer concentrations from 105 to 109 molec cm−3 and temperatures from 248 to 348 K and found that heterodimer stability forms a lognormal relationship with J4×4. However, temperature and concentration effects made it difficult to form a predictive expression of J4×4. In order to reduce those effects, heterodimer concentration was calculated from heterodimer stability and yielded an expression for predicting J4×4 for any salt, given approximately equal acid and base monomer concentrations and knowledge of monomer concentration and temperature. This parameterization was tested for the sulfuric acid–ammonia system by comparing the predicted values to experimental data and was found to be accurate within 2 orders of magnitude. We show that one can create a simple parameterization that incorporates the dependence on temperature and monomer concentration on J4×4 by defining a new term that we call the normalized heterodimer concentration, Φ. A plot of J4×4 vs. Φ collapses to a single monotonic curve for weak sulfate salts (difference in gas-phase acidity >95 kcal mol−1) and can be used to accurately estimate J4×4 within 2 orders of magnitude in atmospheric models.

Thermal Properties and Structural Features of Multilayer Films Based on Chitosan and Anionic Polysaccharides.

This study investigates the thermal and structural properties of multilayer composites based on chitosan (CS) and polyanions with different functionalities, including sodium sulfoethyl cellulose (SEC), sodium alginate (ALG), and sodium hyaluronate (HA). Unlike polyelectrolyte complexes (PECs) obtained by polymer mixing, the formation of a PEC layer by a process of layer-by-layer deposition of oppositely charged polymers is accompanied by the transformation of the CS polymorphic state, and this affects the relaxation and thermal properties of the resulting multilayer composite. X-ray diffraction analysis showed that the formation of the PEC layer in the CS/SEC multilayer film is accompanied by crystallization of the CS chains and the formation of a predominantly anhydrous CS modification. Thermogravimetric analysis of the CS/SEC film registers a high-temperature peak associated with the thermal decomposition of crystalline CS in the PEC composition. According to the dynamic mechanical analysis, the CS/SEC composite was characterized by a single glass transition temperature, indicating a strong interaction between the layers when using SEC (a strong acid salt) as the counterion to CS. For multilayer composites with weak polyacid salts (ALG and HA), the crystallization of CS in the PEC layer is weaker, as reflected in the thermal degradation of these films. A high-temperature peak is recorded in the thermal decomposition of CS/HA and is absent in the case of CS/ALG. Dynamic mechanical analysis of the CS/ALG composite showed two glass transition temperatures close to those of the original polymers, indicating weak PEC formation. The CS/HA composite showed an intermediate response. Thus, the effect of the PEC layer on the properties of the poly-layer composites decreases in the order CS/SEC > CS/HA > CS/ALG.

Barium concentration, phytoavailability, and risk assessment in soil-rice systems from an active barium mining region

Barium (Ba) is a non-essential and toxic element. In China, intensive Ba mining and Ba salt manufacturing have led to sharp increases in Ba in the environment, but little information is available regarding Ba concentrations in paddy soil and rice. The total concentrations and phytoavailability of Ba in paddy soils and paired rice samples collected from the world's largest Ba mine in Dahebian, Tianzhu, Guizhou Province, southwestern China, were investigated. Risk assessments of Ba exposure via rice consumption were also evaluated. The results indicated that extremely high Ba concentrations existed in paddy soils, ranging between 518 mg/kg and 65,760 mg/kg, which demonstrated severe Ba contamination, as expected. The concentrations of rice Ba varied from 0.10 to 3.5 mg/kg, and a significantly positive correlation (r = 0.51, p < 0.05) between rice Ba and water-extractable Ba was observed, suggesting that water, rather than weak acid (0.43 M CH3COOH), chelating agents (DTPA) or neutral salts (0.1 M NaNO3, 0.01 M CaCl2 or 1 M NH4OAc), is a suitable extractant for predicting the phytoavailable Ba in the studied soils. Risk assessments showed that residents experienced low Ba exposure via rice consumption when considered in isolation of other sources in this study area.

Mass production of low-boiling point solvent- and water-soluble graphene by simple salt-assisted ball milling.

Developing a mass production method for graphene is essential for practical usage of this remarkable material. Direct exfoliation of graphite in a liquid is a promising approach for production of high quality graphene. However, this technique has three huge obstacles to be solved; limitation of solvent, low yield and low quality (i.e., multilayer graphene with a small size). Here, we found that soluble graphite produced by mechanochemical reaction with salts overcomes the above three drawbacks. Soluble graphite was exfoliated into monolayer graphene with more than 10% yield in five minutes of sonication. The modified graphite was easily exfoliated in a low-boiling point solvent such as acetone, alcohol and water without the aid of a surfactant. Molecular simulation revealed that the salt is adsorbed to the active carbon at the graphite edge. In the case of weak acid salts, the original bonding nature between the alkali ion and the base molecule is retained after the reaction. Thus, alkali metals are easily dissociated in a polar solvent, leading to negative charge of graphene, enabling the exfoliation of graphite in low boiling point solvents. The approach proposed here opens up a new door to practical usage of the attractive 2D material.

Mechanochemical reaction using weak acid salts enables dispersion and exfoliation of nanomaterials in polar solvents

Nanomaterials, such as carbon nanotubes, graphene, and various types of nanosheets, form aggregates in dry powder due to attractive van der Walls forces. To bring out their unique properties, dispersion of the nanomaterial in solid or liquid is essential. However, the dispersion media for these materials are limited; the surface tension of liquid should be as close as possible to that of the nanomaterial. This limitation restricts the effective usage of nanomaterials. Here, we find that nanomaterials are easily dispersed or exfoliated in water and low-boiling point solvents after simple pretreatment. Pulverization of nanomaterials induces many dangling bonds at the newly created edge, and these active species react with weak acid salts. In polar solvent, the bonded salts are dissociated and enhance the negative charging of nanomaterials. The enhanced electric charging prevents the aggregation or restacking of nanosheets even in typically incompatible solvent such as water and alcohol. The functionalized powder can be easily exfoliated, giving more than 20% yield of nanosheets after only 5 min of sonication.

Direct exfoliation of layered materials in low-boiling point solvents using weak acid salts

The method for mass production of nanosheets is essential for fully realizing their commercial use. Direct exfoliation of layered materials in liquid is the simplest and low-cost technique for exfoliation without introducing defects in basal plane. However, the technique requires toxic and high-boiling point solvents, which makes it difficult for further processing. In addition, solvent exchange involves time-consuming processes such as filtering and redispersion. A breakthrough is necessary to make 2D-crystal-based functional dispersions. Here, we find a new method to directly exfoliate layered materials in low-boiling point solvents. Addition of small amounts of salt prevents reaggregation of exfoliated nanosheets and improves electrical repulsion. In this process, the mechanical force applied by sonication generates active carbon species at the fractured surfaces, leading to a reaction between the active carbon and the salt in liquid. High concentration graphene dispersions (1 g/L) can be obtained in isopropanol with only 5 min of sonication. We also confirm salt-assisted exfoliation is effective for the other 2D crystals such as MoS2 and boron nitride in a wide variety of polar solvents. Direct exfoliation in processable solution opens up a range of large-area applications such as high performance nanocomposites and coatings.

Experimental study on performance of silica gel and potassium formate composite desiccant coated heat exchanger

In this paper, composite silica gel and potassium formate as typical organic weak acid salts is proposed to use in desiccant coated heat exchanger (DCHE). An experimental study on dynamic adsorption performance of desiccant coated metal sheet samples is conducted to obtain results with different proportions of silica gel and potassium format. A DCHE testing platform is then used to compare thermodynamic performance between single silica gel coated heat exchanger (SCHE) and composite potassium formate and silica gel coated heat exchanger (PSCHE). It is found that impregnating potassium formate into porous silica gel is an effective method to improve adsorption capacity, and 75% saturated potassium formate solution is recommended to constitute composite desiccant under experimental conditions. Compared with SG coated sheet, on average the maximum adsorption mass of SG&0.75PF coated sheet increases 2–3 times. Besides, PSCHE can obtain about 20% higher moisture removal capacity compared with SCHE under experimental condition, meaning the utilization of composite silica gel and potassium formate desiccant can effectively improve dehumidification capacity. PSCHE also can obtain 50% higher total cooling capacity compared with SCHE.

Effects of Various Alcohols and Salts on the Mixed Micellization of Cationic Surfactant (CPC) with Nonionic Surfactant (TX-100)

The values of critical micelle concentration for the mixed micellization of cetylpyridinium chloride (CPC) with polyoxyethylene (10) p-isooctylphenyl ether (TX-100) were measured as a function of overall mole fraction of CPC (α1) at 298.15K by using the UV–Vis spectrophotometric method. Various thermodynamic parameters were calculated and analyzed by the equations derived from the non-ideal mixed micellar model. The results show that there is a strong interaction between two surfactants in a micellar state so that a great negative deviation has been occurred for the micellization of CPC/TX-100 mixed system. A straight long alcohol makes greater effects than a branched short alcohol. Alcohols are affecting only the activity of nonionic surfactant in a micellar state, but salts are affecting both the activities of cationic surfactant (CPC) and nonionic surfactant (TX-100). We can also know that strong inorganic salts are more effective than weak organic salts on the micellization of the CPC/TX-100 mixed system.

Influence of electro-activated solutions of weak organic acid salts on microbial quality and overall appearance of blueberries during storage

The aim of this work was to study the potential of diluted electro-activated solutions of weak organic acid salts (potassium acetate, potassium citrate and calcium lactate) to extend the shelf life of blueberries during post-harvest storage. The sanitizing capacity of these solutions was studied against pathogenic bacteria Listeria monocytogenes and E. coli O157:H7 as well as phytopathogenic fungi A. alternata, F. oxysporum and B. cinerea. The results showed that a 5-min treatment of inoculated blueberries with electro-activated solutions resulted in a 4 log CFU/g reduction in Listeria monocytogenes for all solutions. For E. coli O157:H7, the electro-activated potassium acetate and potassium citrate solutions achieved a decrease of 3.5 log CFU/g after 5 min of berry washing. The most important fungus reduction was found when blueberries were washed with an electro-activated solution of potassium acetate and a NaOCl solution. After 5 min of blueberry washing with an electro-activated potassium acetate solution, a very high reduction effect was observed for A. alternata, F. oxysporum and B. cinerea, which showed survival levels of only 2.2 ± 0.16, 0.34 ± 0.15 and 0.21 ± 0.16 log CFU/g, respectively. Regarding the effect of the washing on the organoleptic quality of blueberries, the obtained results showed no negative effect on the product color or textural profile. Finally, this work suggests that washing with electro-activated solutions of weak organic acid salts can be used to enhance the shelf-life of blueberries during post-harvest storage.

Utilization of “Titanium White” Waste as Raw Material in Preparation of Poly-Ti–Fe (M-PTF) Coagulant: Changes in Characteristics During Aging Process

A poly-Ti–Fe (M-PTF) coagulant was prepared using a kind of “waste acid filter cake (WAFC)” derived from production process of “titanium white” as a raw material. The impact of aging process on the micro-characteristics of M-PTF was investigated with scanning electron microscopy (SEM), pH meter and UV spectrophotometer (UV), respectively, and coagulation performance in treating a simulated dyeing wastewater was then studied. The results indicated the following changes occurred with the increasing of aging time: the proportion of middle or high polymer part in M-PTF increased, the amount of crystalline-like structure having smooth surface morphology in the mixed netlike structure consisted of non-crystalline and crystalline-like structure increased, gradual conversion occurred from a strong acid weak base salts or acid salts to strong base weak acid salts or basic salts, and the structure and composition basically tended to be stable after aging 10 days. Removal efficiency of pollutants by M-PTF decreased with the increasing of aging time: removal of turbidity, organic matters and color reached 97, 76 and 97 %, and 61, 8 and 66 % at aging time of 1 and 26 days, respectively. Using WAFC to prepare coagulants is a feasible way, and controlling the growth of crystalline-like structure is one of the key factors to improve the stability of storage and removal efficiency of M-PTF.

Biphasic dissolution method for quality control and assurance of drugs containing active substances in the form of weak acid salts.

Substances in the form of weak acid salts have been found to be problematic for dissolution testing. Their absorption can start only after they are turned into the form of an acid following the gastric passage although they were administered in the form of a salt. Due to poor solubility, they cannot be tested in acidic gastric environment for a biased dissolution profile. The biphasic dissolution method is promising for overcoming this obstacle. Tablets with warfarin clathrate sodium salt in two concentrations and two different particle size distributions were tested as a suitable model for finding the medium and process conditions of dissolution. The dissolution method based on the use of the upper organic layer (1-octanol) and the lower aqueous layer 0.1 mol L(-1) HCl) was found suitable and discriminatory for tablets containing active substances in the form of salts of weak acids. The method also reflects physical differences in the quality of used substances.

Analysis of trace inorganic anions in weak acid salts by single pump cycling-column-switching ion chromatography.

The application of ion chromatography with the single pump cycling-column-switching technique was described for the analysis of trace inorganic anions in weak acid salts within a single run. Due to the hydrogen ions provided by an anion suppressor electrolyzing water, weak acid anions could be transformed into weak acids, existing as molecules, after passing through the suppressor. Therefore, an anion suppressor and ion-exclusion column were adopted to achieve on-line matrix elimination of weak acid anions with high concentration for the analysis of trace inorganic anions in weak acid salts. A series of standard solutions consisting of target anions of various concentrations from 0.005 to 10 mg/L were analyzed, with correlation coefficients r ≥ 0.9990. The limits of detection were in the range of 0.67 to 1.51 μg/L, based on the signal-to-noise ratio of 3 and a 25 μL injection volume. Relative standard deviations for retention time, peak area, and peak height were all less than 2.01%. A spiking study was performed with satisfactory recoveries between 90.3 and 104.4% for all anions. The chromatographic system was successfully applied to the analysis of trace inorganic anions in five weak acid salts.

Uptake of Bile Acid into Calcium-Induced Alginate Gel Beads Containing &amp;lt;i&amp;gt;β&amp;lt;/i&amp;gt;-Chitosan Weak Acid Salt

Recently, potential applications for β-chitosan (β-CS) have been examined. In the present study, calcium-induced alginate gel beads (Alg-Ca) containing weak acid salts of β-CS were prepared and examined with regard to their ability to adsorb bile acids in vitro. More than 70% of taurocholate dissolved in solution was taken up by Alg-Ca containing 100 mg β-CS, sim. ilar to the degree of uptake observed with Alg-Ca containing α-CS salt. The adsorption of bile acid was affected by the absolute amount of β-CS and/or the acid concentration of the preparation. A secondary bile acid, taurodeoxycholate, was also adsorbed by Alg-Ca containing weak acid salts of β-CS. Therefore, β-CS might be used to adsorb bile acids within the gastrointestinal tract in the same manner as an anion-exchange resin, and thus serve as a complementary means by which to prevent hyperlipidemia.

PH-sensitive fluorescent salicylaldehyde derivative for selective imaging of hydrogen sulfide in living cells

The salicylaldehyde derivative, 9-formyl-8-hydroxyjulolidine was developed as a fluorescent probe to detect weak acid ions. With the salicylaldehyde moiety as the chromophore, the probe exhibits pH sensitive detection of hydrogen sulfide and silicate in aqueous solution. It displays an excellent selectivity for hydrogen sulfide and silicate over other weak acid salts. Time-dependent density functional theory calculations confirmed that the fluorescence turn-on mechanism involved blocking intramolecular charge transfer. The probe detects S2− in live cells, providing a powerful method to study H2S chemistry in biological systems.