Saturated Aqueous Solution Research Articles

Synthesis of a Novel Zwitterionic Hypercrosslinked Polymer for Highly Efficient Iodine Capture from Water.

Cationic porous organic polymers have a unique advantage in removing radioactive iodine from the aqueous phase because iodine molecules exist mainly in the form of iodine-containing anions. However, halogen anions will inevitably be released into water during the ion-exchange process. Herein, we reported a novel and easy-to-construct zwitterionic hypercrosslinked polymer (7AIn-PiP)-containing cationic pyridinium-type group, uncharged pyridine-type group, pyrrole-type group, and even an electron-rich phenyl group, which in synergy effectively removed 94.2% (456 nm) of I2 from saturated I2 aqueous solution within 30 min, surpassing many reported iodine adsorbents. Moreover, an I2 adsorption efficiency of ~95% can still be achieved after three cyclic evaluations, indicating a good recycling performance. More importantly, a unique dual 1,3-dipole was obtained and characterized by 1H/13C NMR, HRMS, and FTIR, correlating with the structure of 7AIn-PiP. In addition, the analysis of adsorption kinetics and the characterization of I2@7AIn-PiP indicate that the multiple binding sites simultaneously contribute to the high affinity towards iodine species by both physisorption and chemisorption. Furthermore, an interesting phenomenon of inducing the formation of HIO2 in unsaturated I2 aqueous solution was discovered and explained. Overall, this work is of great significance for both material and radiation protection science.

Selective adsorption and corrosion mechanism of SO2 and its hydrates on X65 welded joints steel in CO2-saturated aqueous solution

In this study, the corrosion mechanism in different regions of the welded joints in CO2/SO2 saturated aqueous solution was investigated by electrochemistry and morphological analysis. The results demonstrated that SO2 and its hydrolysis have some adsorption properties and tend to adsorb in the region of the base metal and generated FeS product. A dense corrosion product film could form on this region, effectively reducing the corrosion rate. Due to the selective adsorption which increases the potential difference between different regions of the welded joint, further intensifying the galvanic corrosion and ultimately leading to the failure of the welded joint.

Two rhombic ice phases from aqueous salt solutions under graphene confinement.

Water exhibits rich ice phases depending upon its respective formation conditions, and in particular, the two-dimensional ice with nonhexagonal symmetry adsorbed on solids relates to the exceptional arrangement of water molecules. Despite extensive reporting of two-dimensional ice on various solid surfaces, the geometry and thermodynamics of ice formation from an aqueous salt solution are still unknown. In this Letter, we show the formation of single- and two-phase mixed two-dimensional rhombic ice from aqueous salt solutions with different concentrations under strong compressed confinement of graphene at ambient temperature by using classical molecular dynamics simulations and first-principles calculations. The two rhombic ice phases exhibit identical geometry and thermodynamic properties, but different projections of the oxygen atoms against solid surface symmetry, where they relate to the stable and metastable arrangements of water molecules confined between two graphene layers. A single-phase rhombic ice would grow from the confined saturated aqueous solutions since the previously stable rhombic molecular arrangement becomes an unstable high-energy state by introducing salt ions nearby. Our result reveals different rhombic ice phases growing from pure water and aqueous solutions, highlighting the deciding role of salt ions in the ice formation process due to their common presence in liquids.

An Efficient Propylphosphonic Anhydride (T3P®)-Mediated MW-induced Solvent-free Rapid Synthesis of Enamino Esters and Ketones including 5, 5-Dimethyl-3-aminocyclohex-2-enones

Abstract: This work presents a clean and convenient synthesis of various β-enaminones including 5,5- dimethyl-3-aminocyclohex-2-enones, in satisfactory to excellent yields from the condensation reaction of primary amines with β -dicarbonyls by employing T3P® as a catalyst and performing the reaction under microwave irradiation and solvent-free conditions. These rapid reactions launched readily and stood a diversity of organic functional groups. A mixture of 1,3-dicarbonyl compound, primary amine and T3P® (50% in AcOEt) was irradiated for an appropriate time under microwave at 80°C. After completing the reaction (TLC) and cooling to r.t., ethyl acetate and saturated aqueous NaHCO3 solution were added. The aqueous phase was extracted ethyl acetate. The combined organic layer was washed with brine, dried over Na2SO4, and filtered, and the solvent was removed under reduced pressure to afford the product, which was recrystallized from diisopropyl ether. The presented results exhibit a better catalytic activity of T3P in the synthesis of enaminones. It could be concluded that T3P is the best catalyst as it took only a few minutes for the completion of the reaction with an excellent yield of product, which indicates T3P is more efficient, compared to other catalysts. A comparison of the efficiency of the present procedure with some heterogeneous solid catalysts was evaluated as well. Clearly, a higher yield was established in this procedure compared to other catalysts. Furthermore, the reaction of amines with dimedone was investigated as well, delivering excellent yields. The reaction catalyzed by T3P under microwave irradiation supplies a comprehensive method for the synthesis of enaminones. In this work, T3P is an effective, efficient and green catalyst, which forms the procedure economic, suitable, and safe with widespread application in the synthesis of enaminones. background: This work presents a clean and convenient synthesis of various β-enaminones incuding 5,5-dimethyl-3-aminocyclohex-2-enones in good to excellent yields from the reaction of different primary amines with 1,3-dicarbonyl compounds by employing T3P® as a catalyst and performing the reaction under microwave irradiation and solvent-free conditions. This one-pot rapid reaction proceeded readily and tolerated a variety of functional groups.

The efficiency of micellar solubilization of naphthalene from aqueous solutions using rhamnolipid as a biological surfactant according to NMR diffusometry.

The micellar solubilization of naphthalene from its saturated aqueous solutions using the biosurfactant rhamnolipid was studied. Using the NMR diffusion method, selective measurements of the self-diffusion coefficients of molecules of all components of the solution-naphthalene, rhamnolipid, and water-were carried out at various rhamnolipid concentrations from 0.06 to 100 g/L. Based on the results of diffusometry, the distribution of naphthalene molecules between the states free in solution and states bound by micelles was found. With an increase in the concentration of rhamnolipids, the proportion of bound naphthalene molecules increases from 50% at CRL = 2g/L to 100% at CRL ≥ 50 g/L. The micelle-water partition coefficient Km and the molar solubilization ratio MSR were calculated.

Evaporation of a heated saline marble: Interplay of interfacial and thermal effects

A multistage evaporation of continuously heated liquid marbles, coated with polytetrafluoroethylene colloidal particles was investigated experimentally and theoretically. Liquid marbles initially contained an almost saturated aqueous NaCl solution. Numerical heat transfer calculations and analytical evaluations of initial evaporation showed that the equilibrium marble temperature and saturated salt concentration are reached relatively rapidly compared to the “long” marble evaporation time. This means that a typical long period of marble evaporation is determined by the low permeability of the salt crust formed beneath the marble colloidal shell. A theoretical estimation of the total evaporation time of marble water based on Darcy's law for the porous crust and the marble shell is suggested. A comparison with experimental data allowed obtaining an approximate value of the very low permeability of this bilayer barrier to marble evaporation. The proposed phenomenological model of the saline marble evaporation provides insight into why marble evaporation is so slow.

Microencapsulation of star anise essential oil: Preparation, characterization, in vitro digestion, and biological activity

Star anise essential oil (SAEO) has garnered significant attention for its potent bioactivities. However, the instability and poor water solubility of SAEO limit its application in the food and pharmaceutical industries. To overcome these challenges and improve bioavailability, we encapsulated SAEO within β-cyclodextrin (β-CD) using a saturated aqueous solution method. Characterization techniques including Fourier transform infrared spectroscopy, Scanning electron microscopy, X-ray diffraction, and Thermogravimetric-differential scanning calorimetry confirmed the successful formation of SAEO and β-CD inclusion complex (SAEO-IC) with good thermal stability. The inclusion complex had a yield of 63.18 ± 3.18% and an oil content of 9.32 ± 0.36%. In vitro digestion studies revealed the stability of SAEO-IC in gastric conditions, with the primary release of active ingredients occurring in the intestine. Moreover, the encapsulation process preserved the antioxidant properties of SAEO and demonstrated enhanced antimicrobial and anti-tumor activity, suggesting that SAEO-IC has the potential to serve as a natural antimicrobial and anticancer agent.

Robust and stable organic sulfonate sodium salt-coated superhydrophilic mesh for ultra-fast gravity-drive oil-water separation

Due to its special wetting behavior and high selectivity, super-wetting mesh is considered as an ideal candidate material for efficient separation of water/oil mixture. However, the oil-water separation mesh suffers from the problems of poor stability and durability, leading to the failure of the separation. In this paper, a robust and stable superhydrophobic/superhydrophilic copper mesh had been successfully prepared by decorating the copper mesh via the chemical grafting of the 3-thiol-propyl trimethoxysilane (KH590) and the subsequent reaction with 2-acrylamide-2-methylpropane-1-sulfonate sodium (AMPS). It showed that the KH590 condensation compound was tightly coated on the surface and the superhydrophobic copper mesh (SUCM) possessed excellent superhydrophobicity towards various liquid droplets with a WCA of higher 150° and a sliding angle lower 5°, while the superhydrophilic copper mesh (SICM) had promising anti-oil pollution property with WCA near 0°. The SUCM and SICM also had excellent acid and alkali resistance. The obtained SICM had preeminent separation efficiency higher 99% and extremely high permeability flux of 33,441 L·m−²·h−¹ for gravity-driven toluene-water separation, and possessed excellent recyclability even after 20 cycles. Moreover, the SICM could be used to separate the oil-water mixture of aqueous solution with different pH (pH=5/7/8) and aqueous sodium chloride solution with different concentrations (5%/25%/50%/saturated aqueous sodium chloride solution). In addition, the SICM had outstanding anti-abrasion mechanical stability. This work provided a simple and effective method for the preparation of special wettability materials with excellent acid/alkali resistance and mechanical stability, and promoted the practical application of oil/water separation mesh.

NaI as suitable alkali halide hydrate for domestic thermochemical heat storage

The limits and potentials of alkali (Li - Cs) halides (F - I) as salt hydrate-based thermochemical heat storage materials are studied. Most alkali halides are found unsuitable, and only the hydrates of sodium iodide (NaI) and sodium bromide (NaBr) were investigated experimentally. We confirmed that both have high energy densities of 1.5 GJ/m3 and 1.6 GJ/m3 respectively, based on the crystal structures of the dihydrate phases. NaI demonstrated full cyclic stability at water vapor pressures of 12 and 14.5 mbar, but NaBr did not show rehydration at these conditions. Therefore, NaBr was deemed unsuitable for domestic applications. For the NaI – H2O system, we have measured the p,T equilibrium line between the hydration states and constructed p,T and T,x – phase diagrams. This showed that the hydration temperature is 42 °C for 12 mbar water vapor pressure which is enough for domestic space heating. Additionally, the phase diagrams revealed an incongruent melting point where the NaI·2H2O is in equilibrium with the anhydrate and a saturated aqueous NaI solution. This melting can overlap with dehydration and thereby hinders the cyclability, since in the melting process part of the salt is dissolved which blocks the pores formed during dehydration. Therefore, the performance of NaI can be improved by ensuring dehydration is completed below the incongruent melting point of 68 °C. We also found that pre-cycling can prevent deliquescence which is expected to occur at 25 °C and 12 mbar. Overall, NaI could be a candidate for low temperature heat storage.

Solar Hydrogen Production by (HA)PbX4 (X = I, Br) 2D Perovskite Crystals Doped with MoS2

Halide perovskites have gained significant attention in the field of photovoltaics and photocatalysis due to their exceptional optoelectronic properties. However, the exploration of other classes of 2D perovskite materials is limited. In this work, the photocatalytic performance of (HA)PbX4 2D crystals embedded with MoS2 in their bulk structure is investigated. The (HA)PbX4@MoS2 composites are directly synthesized in a (HA)PbX4 crystal solution. Notably, the (HA)PbI4@MoS2 composite exhibits a remarkable 2.94‐fold increase in H2 evolution activity. Furthermore, the composite demonstrated stability in a (HA)PbX4 (HA = histamine, X = I, Br, Cl)‐saturated aqueous HX solution. The photogenerated electrons in (HA)PbX4 are efficiently transferred to the MoS2 sites, facilitating the reduction of protons to H2. In this study, the potential of hybrid 2D perovskite–MoS2 composites is highlighted as promising visible‐light photocatalysts for aqueous solution applications.

Deep eutectic solvents vs. Aqueous acids in metal extraction from animal tissues

This study is the first to thoroughly compare the efficiency of ultrasonic extraction of heavy metals (Cu, Cd, Co, Cr, Fe, Pb and Zn) from solid-phase food products using acidic deep eutectic solvents and saturated aqueous solutions of these acids (lactic, citric, tartaric, glycolic, malonic, malic). Atomic emission spectral analysis with inductively coupled plasma is used for the sensitive and selective determination of metals in extracts. The work shows that eutectic solutions more effectively extract all the studied metals compared to aqueous solutions of acids (extraction efficiency of 85–95 %), which is comparable to the results obtained with complete mineralization of the sample using microwave mineralization. However, the proposed procedure is much more environmentally friendly, since it does not require oxidizing mixtures and does not generate dangerous nitrogen oxides. The highest extraction efficiency is achieved when using lactic acid. Also, in the work, the extraction mechanism was studied for the first time, and the contribution of choline chloride to the extraction efficiency was demonstrated. The proposed method made it possible to determine metals at a level from 0.33 to 0.8 mg kg−1, and was used to analyze real samples of chicken meat and certified reference material of beef liver.

Enhancing capillary action of acidified paper to achieve uniform deacidification and long-lasting aging resistance

Deacidification is a necessary and urgent means of protecting acidified paper documents. However, the contradiction between deacidification efficiency and uniformity in existing aqueous or organic phase deacidification methods has not been resolved yet, which is mainly attributed to the differences in capillary action of paper on solvents with different polarities. In this work, a strategy of two-phase deacidification was proposed to achieve efficient and uniform deacidification and long-lasting aging resistance. Impregnation of nano magnesium oxide organic dispersion of deacidified paper achieved efficient batch deacidification and sufficient alkali reserve. Using ultrasonic atomization of saturated calcium hydroxide aqueous solution, the penetration of alkaline substances into paper promoted uniform deacidification based on strong capillary action. Meanwhile, microstructural reinforcement of paper fibers was achieved based on the multiple interactions. This method can endow the treated paper with better thermal stability and long-lasting aging resistance. After artificial accelerated aging for 30 d, the treated paper samples still maintained the highest tensile index (18.46 Nm/g), folding endurance (8.5 times), tear index (3.95 mN·m2/g) and displayed negligible chromatic aberration (∆E = 2.46 ± 0.21). This method greatly extends the lifespan of acidified paper, which has significant value for the protection of paper documents.

Surface passivation of red-emitting fluoride phosphors by aminocarboxyl complexants to achieve high water-resistance for light-emitting diodes

Mn4+-activated fluoride phosphors are promising luminescent materials for use in phosphor-converted white-light-emitting diodes (wLEDs). However, poor water resistance in high humidity environment, one of critical drawbacks of this type of phosphors, has limited their practical applications. To address this issue, we developed a new facile strategy to passivate the surface of phosphors by in situ constructing a dual Mn4+-rare protective layer using well-known aminocarboxyl complexants with mild reducibility and strong complexation property. Ethylenediamine tetraacetic acid (EDTA) was taken as a representative for the research in detail, and a typical Mn4+-doped fluorosilicate phosphor K2SiF6:Mn4+ (KSFM) was selected to demonstrate the reliability of the proposed strategy. The surface passivation was achieved by simply dispersing KSFM in a saturated EDTA aqueous solution (KSFM-sEDTA) or a hydrofluoric acid solution containing a certain amount of EDTA (KSFM-EDTA), and then stirring for a short time at room temperature. The analysis results indicate that the dual Mn4+-rare surface layer is composed of a K2SiF6 matrix shell and an organic coating of residual EDTA and/or its related compounds, and the layer constructed by Method 2 is more significant than that by Method 1. Both the luminescence performance and the water resistance of the passivated KSFM were greatly enhanced while the luminescence characteristics remained unchanged. When the water-eroded KSFM was re-treated with EDTA, the luminescence was dramatically restored due to removal of the manganese hydrolysates and repair of the crystal surface defects. The wLEDs assembled with KSFM-EDTA and KSFM-sEDTA phosphor exhibited intense white light with high luminous efficiency (LE, 170.61 lm/W and 162.51 lm/W), high color rendering index (CRI, 88.3 and 85.9), and low correlated color temperature (CCT, 3680 K and 3805 K), respectively. More importantly, the fabricated wLEDs retained high LE (90.6% and 88.6%) and no remarkable changes of CRI and CCT values after being aged at high temperature and humidity (85 °C, 85%) for 550 h, which are more superior to the wLED assembled with the pristine KSFM.

On the relation between maximal thermal performance and minimal fouling deposition rate in heat exchanger-like devices

The present article numerically studies the relationship between a heat exchanger’s thermal performance and the occurrence of fouling, here represented by the deposition of calcium sulfate (CaSO4) on its surface. For that, a 2D geometry denoting the internal flow of a CaSO4 saturated aqueous solution between two parallel plates is simulated. The flow, which can be laminar or turbulent (k-ω SST model), is promoted by a known pressure difference across the channel, while the CaSO4 fouling is thermally triggered by a heat source in the central part of the channel. The numerical model considers the solution of the conservative equations of mass, momentum, and energy, while the mass transfer rate is determined based on a correlation available in the literature. Two approaches were used to determine the CaSO4 fouling rate: (i) the CaSO4 concentration on the fouling’s surface was assumed to be identical to the concentration of the bulk flow, and (ii) the fouling concentration varies spatially, hence requiring the solution of the differential equation for conservation of species. The steady analysis showed that for both approaches, the optimal plate-to-plate spacing that maximizes the thermal performance is similar to the spacing that minimizes the fouling deposition. Finally, the transient analysis, which also considers the effect of the fouling removal rate through shear, shows that deviations might occur between the optimal spacings for maximal thermal performance and minimal deposition, especially for lower pressure drop values.

Studies on Loading Salicylic Acid in Xerogel Films of Crosslinked Hyaluronic Acid.

During the last decades, salicylic acid (SA) and hyaluronic acid (HA) have been studied for a wide range of cosmetic and pharmaceutical applications. The current study investigated the drug loading potential of SA in HA-based crosslinked hydrogel films using a post-loading (osmosis) method of the unmedicated xerogels from saturated aqueous solutions of salicylic acid over a range of pH values. The films were characterized with Fourier-transform infra-red spectroscopy (FT-IR) and ultraviolet-visible (UV-Vis) spectrophotometry in order to elucidate the drug loading profile and the films' integrity during the loading process. Additional studies on their weight loss (%), gel fraction (%), thickness increase (%) and swelling (%) were performed. Overall, the studies showed significant film disintegration at highly acidic and basic solutions. No drug loading occurred at neutral and basic pH, possibly due to the anionic repulsion between SA and HA, whereas at, pH 2.1, the drug loading was promising and could be detected via UV-Vis analysis of the medicated solutions, with the SA concentration in the xerogel films at 28% w/w.

Development of a Multifunctional Composite Hydrogel for Enhanced Wound Healing: Hemostasis, Sterilization, and Long-Term Moisturizing Properties.

Meeting the diverse requirements of effective wound repair while surpassing the single-function limitations of traditional wound dressings is a significant challenge. In this study, we successfully synthesized an inclusion complex of 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) and iodine using the saturated aqueous solution method. Additionally, dialdehyde cellulose (DAC) was extracted from fat-free cotton through oxidation. To enhance wound healing, l-glutamine (l-glu) was utilized as a functional molecule, resulting in composite hydrogels with hemostatic, sterilizing, and wound-healing-promoting properties that were achieved by adsorbing the resulting inclusion complex. Through TG and SEM analysis, we confirmed that iodine was effectively accommodated by cyclodextrin and was uniformly attached to the hydrogel. The hydrogel exhibits exceptional long-term moisturizing and bactericidal properties, while also demonstrating excellent swelling, oxygen permeability, hemolytic, and mechanical properties, fully satisfying the requirements of wound treatment. External coagulation tests revealed that the hydrogel can rapidly coagulate 4.5 times its own weight of blood. Moreover, in a full-thickness scald mouse model, the hydrogel effectively promotes wound healing. The development of this multifunctional composite hydrogel presents a novel approach to advance wound dressing research, holding substantial potential for practical applications.

Ultrasound-assisted separation and crystallization of metacetamol polymorphs

The nucleation control, separation and crystallization of the polymorphs of the API metacetamol from saturated aqueous solution have been achieved first time on application of different ultrasound process parameters.

Separation and nucleation kinetics of l-menthol polymorph through a swift cooling crystallization process

The form-II polymorph of l-menthol was successfully isolated by a novel swift cooling crystallization process with various supersaturation levels using a saturated aqueous solution and wholly inhibited form-I of l-menthol.

PHASE CONCENTRATION EQUILIBRIUM DURING DRYING COLLOID CAPILLARY-POROUS MATERIAL - PEA

In this work, we studied experimentally the phase concentration equilibrium during drying of a colloidal capillary-porous material - peas. The studies were carried out by a static (exsicator) method using saturated aqueous solutions of mineral salts, with the help of which certain relative air humidity was created in the desiccators. To establish equilibrium, the samples were kept in desiccators for one month. The values of relative air humidity over salt solutions at the corresponding temperatures were found from the well-known Schneider diagram. Moisture desorption isotherms were determined, for which high-moisture pea samples were placed in exsicators. The experiments were carried out at three temperatures: 30, 40 and 50 °C. According to the measurement data, moisture desorption isotherms were constructed in the coordinates "relative air humidity - equilibrium moisture content of the material." The resulting desorption isotherms were described by the Henderson equation, for which the values of the coefficients of this equation were found and their statistical evaluation was given. The data on the balance of peas were compared with similar data for other plant colloidal capillary-porous materials: vegetables (carrot and beet cuts), grain crops (rye, wheat and corn grains), and vegetable seeds. A significant influence of the type of culture on the equilibrium moisture content of the material during drying is shown, while the intraspecific influence on the equilibrium moisture content is less important. The obtained data on moisture desorption isotherms during drying can be used for engineering calculations of the kinetics of drying pea grain and for choosing the temperature and humidity conditions for its storage after drying.

Inclusion complex of turmeric essential oil with hydroxypropyl-β-cyclodextrin: Preparation, characterization and release kinetics

The application of turmeric essential oil (TEO), a natural effective antibacterial agent, in food preservation is limited due to high volatility and low stability. This study aimed to improve its stability and release behavior by synthesizing TEO/hydroxypropyl-β-cyclodextrin (HP-β-CD) inclusion complex (IC) in a saturated aqueous solution. An orthogonal experimental design was used to determine the optimal process conditions (HP-β-CD to TEO, g/mL), 16:1; stirring speed, 850 r/min; encapsulation time, 2 h), achieving a comprehensive score value of 85.62% for TEO/HP-β-CD-IC. Through comprehensive characterization, the results showed that TEO was completely embedded in HP-β-CD with increased stability. Free TEO exhibited a weight loss of 67.64% between 30 and 300 °C, while TEO/HP-β-CD-IC had a mass loss of only 9.33%. HP-β-CD and TEO/HP-β-CD-IC showed positive ZP values that were 124.76 mV and 132.16 mV, respectively. The release behavior and release kinetics of TEO/HP-β-CD-ICs were also studied, and the results showed that TEO/HP-β-CD-IC release rate increased under higher temperature and relative humidity—consistent with Fick’s diffusion.