Complexes In Aqueous Solution Research Articles

Regulation of electron delocalization on porous carbon/manganese-iron oxide for enhancing nonradical processes of sulfamethoxazole: Oxidation pathway and mechanism

Transition metal oxide defect engineering can regulate the electronic properties of materials, thereby realizing nonradical reactions during catalytic processes. In this study, porous carbon/manganese-iron oxide (PC@MFO) composites with different Mn/Fe ratios were prepared via in-situ encapsulation strategy. PC@MFO exhibited superior catalytic degradation and stable recycling performance during peroxymonosulfate (PMS) activation to degrade sulfamethoxazole (SMX). After 10 min of reaction, >92 % of SMX was rapidly degraded, with high selectivity, through oxidative SMX removal from a complex aqueous solution. The kinetics of SMX degradation over different as-prepared samples were also investigated. A recycling study and regeneration treatment revealed no clear deactivation between the 1st and 6th cycles, suggesting that PC@MFO is a reusable heterogeneous catalyst for utilization in efficient oxidative SMX removal. Multiple characterization techniques and density functional theory calculations were used to study the mechanism of SMX degradation process. Nonradical oxidation was found to be the dominant reaction in the catalytic reaction, leading to SMX degradation. This was possibly due to the highly conjugated electron delocalization induced by Mn-Fe in the O-octahedra close to the oxygen vacancies, promoting rapid charge transfer and interfacial reaction kinetics. This study expands the understanding for the activation mechanism driven by Mn-Fe spinel oxides in deep-water treatment.

The Theoretical Calculation of the Cu Isotope Fractionation Effect in Solution/Hydrothermal Solution Systems.

Copper (Cu) is an important transition metal, and its isotopes have important applications in geology, environmental science, soil science, and other fields. Cu isotope fractionation can occur in many natural processes. However, the mechanism of Cu isotope fractionation in solution/hydrothermal solution systems is not very clear. In this study, the fractionation effects of complexes of Cu(I) and Cu(II) in solution/hydrothermal solution systems were systematically studied by means of an ab initio method based on first principles. In the simulation of an aqueous solution system, the theoretical treatment method used is the "water-droplet" method. The results show that the heavy Cu isotope (65Cu) enrichment capacity of the Cu-bearing complex solutions is greatly affected by the ligand types both for Cu(I) and Cu(II). For Cu(I) complex solutions, the heavy Cu isotope enrichment sequence is [Cu(HS)2]-·(H2O)42 > [Cu(HS)(H2O)]·(H2O)42 ≈ [Cu(HS)(H2S)]·(H2O)42 > [CuCl]·(H2O)42 > [CuCl2]-·(H2O)42 > [CuCl3]2-·(H2O)42. For the aqueous solutions of Cu(II) with an inorganic ligand (such as H2O, OH-, NO3-, SO42- and CN-), the order of heavy Cu isotope enrichment is as follows: [Cu(H2O)6]2+·(H2O)42 > [Cu(NO3)2]·(H2O)42 > [Cu(OH)2]·(H2O)42 > [CuSO4(H2O)3]·(H2O)42 > [CuNO3(H2O)4]+·(H2O)42 > [CuCN]+·(H2O)42. For the Cu(II) complex solutions with a halogen as ligands, the change order of 1000lnβ is [CuCl]+·(H2O)42 > [CuCl2]·(H2O)42 > [CuBr2]·(H2O)42 > [CuCl3]-·(H2O)42. The sequence of 1000lnβ for Cu(II) organic complex aqueous solutions is [Cu(HOC6H4COO)]+·(H2O)42 > [Cu(CH3CH2COO)]+·(H2O)42 > [Cu(COOHCOO)]+·(H2O)42. The calculation also found that for Cu(I) complex aqueous solutions, the difference in Cu isotope fractionation parameters (1000lnβ) between [CuCl2]-·(H2O)42 and [Cu(HS)2]-·(H2O)42 is relatively large. At 100 °C, the 1000lnβ of the two species are 1.14 and 1.55 (‱), respectively. The difference between the two could be reached up to 0.41 (‱). The Cu isotope fractionation parameter obtained with the "water droplet" method is also very different from the results of previous studies, which indicate that the Cu isotope fractionation behavior of the two is similar. At the same time, the exciting discovery is that the enrichment capacity of heavy Cu isotopes is significantly different between Cu(I) complex aqueous solutions and Cu(II) complex aqueous solutions. At 100 °C, the 1000lnβ of 6 Cu(I) complex aqueous solutions and 13 Cu(II) complex aqueous solutions ranged from 0.90 to 1.55 and 2.24 to 3.25(‱), respectively. It also shows that the REDOX reaction has a significant effect on the Cu isotope fractionation, especially in ore-forming fluids. Therefore, the ligand type is a factor that cannot be ignored when considering the mechanism of Cu isotope fractionation in solution/hydrothermal solution systems. Whether the solvation effect of an aqueous solution is considered or not has a great influence on the numerical values of the final Cu isotope fractionation factors. Hence, the solvation effect of an aqueous solution is an essential determinant in the theoretical calculation of the Cu isotope fractionation factors for Cu-bearing complex solutions.

Open-Framework Vanadate as Efficient Ion Exchanger for Uranyl Removal.

The elimination of uranium from radioactive wastewater is crucial for the safe management and operation of environmental remediation. Here, we present a layered vanadate with high acid/base stability, [Me2NH2]V3O7, as an excellent ion exchanger capturing uranyl from highly complex aqueous solutions. The material possesses an indirect band gap, ferromagnetic characteristic and a flower-like morphology comprising parallel nanosheets. The layered structure of [Me2NH2]V3O7 is predominantly upheld by the H-bond interaction between anionic framework [V3O7]nn- and intercalated [Me2NH2]+. The [Me2NH2]+ within [Me2NH2]V3O7 can be readily exchanged with UO22+. [Me2NH2]V3O7 exhibits high exchange capacity (qm = 176.19 mg/g), fast kinetics (within 15 min), high removal efficiencies (>99%), and good selectivity against an excess of interfering ions. It also displays activity for UO22+ ion exchange over a wide pH range (2.00-7.12). More importantly, [Me2NH2]V3O7 has the capability to effectively remove low-concentration uranium, yielding a residual U concentration of 13 ppb, which falls below the EPA-defined acceptable limit of 30 ppb in typical drinking water. [Me2NH2]V3O7 can also efficiently separate UO22+ from Cs+ or Sr2+ achieving the highest separation factors (SFU/Cs of 589 and SFU/Sr of 227) to date. The BOMD and DFT calculations reveal that the driving force of ion exchange is dominated by the interaction between UO22+ and [V3O7]nn-, whereas the ion exchange rate is influenced by the mobility of UO22+ and [Me2NH2]+. Our experimental findings indicate that [Me2NH2]V3O7 can be considered as a promising uranium scavenger for environmental remediation. Additionally, the simulation results provide valuable mechanistic interpretations for ion exchange and serve as a reference for designing novel ion exchangers.

The stability and geometrical characteristics of solid-liquid interfacial nanobubbles in complex aqueous solution environments

Interface nanobubbles (INBs) have potential applications in various fields, and their existence has been adequately demonstrated. However, the stability and geometric morphology of INBs in complex solution environments remain less clear. In this study, we investigated the stability and geometrical characteristics of INBs exposed to various solution environments both in situ and statistically. We find that INBs in a 40 vol% ethanol-water solution exhibits a decrease in width but an increase in height and contact angle (from the gas side). In cationic, anionic, and nonionic surfactant solutions, the height of INBs tends to increase, accompanied by a reduction in width, resulting in an increase in the contact angle. The observed increase in height may be attributed to the expansion of INBs, which is likely caused by a reduction in surface tension. This suggests that the gas-liquid interface of INBs remains unsaturated by organic moieties in both pure water and solutions of low surfactant concentrations. The increase in contact angle when INBs are exposed to solutions with a lower liquid-gas interfacial tension is contrary to expectations, which may be caused by the increased solid-gas interfacial tension. However, in different concentrations of NaCl solution, the INBs remain stable with minimal changes in their geometrical parameters. Furthermore, the experimental results demonstrate that INBs exhibit strong stability under lateral shear force and strong vertical pressure. The findings of this study contribute to a deeper understanding of the INBs and provide theoretical support for applications related to INBs.

Highly selective capture of cesium using an electrochemically renewable molybdenum-based crystalline adsorbent

The development of highly efficient adsorbents for the capture of 133Cs and the removal of radioactive isotope 137Cs from complex aqueous solutions is crucial for the chemical production and environmental remediation. Herein, Mo-based crystalline adsorbent with sub-nanometer (5.76 Å) channels was successfully prepared and used in electrochemically controlled Cs+ separation process. Crystalline structures of MoIC (HNO3) before and after adsorption of Cs+ were clearly elucidated using powder X-ray diffractometer (PXRD). A more environmentally friendly electrochemical method was employed to achieve easy release and recapture of Cs+. Adsorption comparison experiments revealed that our material clearly outperforms the reported adsorbents for the removal or recovery of trace amount of Cs+ (< 10 mg L−1). Furthermore, MoIC (HNO3) also exhibited excellent selectivity for low concentration of Cs+ over highly excess of competitive cations, such as Mg2+, Ca2+ and K+, which are commonly distributed in brines. The maximum separation factors of Cs+/Mg2+, Cs+/Ca2+ and Cs+/K+ are 1.2 × 105, 1.3 × 104 and 66, respectively. The remarkable selectivity can be attributed to the outstanding ion-sieving ability of sub-nanometer channels based on the differences in ionic radius and hydration energy of these cations. A real brine was introduced to further prove that one complete cycle of electrochemical adsorption and desorption can dramatically reduce the competing ions concentrations up to 980 times. We anticipate that our findings may give the prospect of opening up new path for the efficient separation of Cs+ from brines using molybdenum-based adsorbent via electrochemically controlled process as a green and sustainable way.

Graphene Oxide, Carbon Nanotubes, and Polyelectrolytes-Based Impedanciometric E-Tongue for Estrogen Detection in Complex Matrices.

Currently, it is necessary to maintain the quality of aquifers and water bodies, which means the need for sensors that detect molecules as emerging pollutants (EPs) at low concentrations in aqueous complex solutions. In this work, an electronic tongue (e-tongue) prototype was developed to detect 17β-estradiol in tap water. To achieve such a prototype, an array of sensors was prepared. Each sensor consists of a solid support with interdigitated electrodes without or with thin films prepared with graphene oxide, nanotubes, and other polyelectrolytes molecules adsorbed on them. To collect data from each sensor, impedance spectroscopy was used to analyze the electrical characteristics of samples of estrogen solutions with different concentrations. To analyze the collected data from the sensors, principal components analysis (PCA) method was used to create a three-dimensional plane using the calculated principal components, namely PC1 and PC2, and the estrogen concentration values. Then, damped least squares (DLS) was used to find the optimal values for the hyperplane calibration, as the sensitivity of this e-tongue was not represented by a straight line but by a surface. For the collected data, from nanotubes and graphene oxide sensors, a calibration curve for concentration given by the 10PC1×0.492-PC2×0.14-14.5 surface was achieved. This e-tongue presented a detection limit of 10-16 M of 17β-estradiol in tap water.

Dissolution kinetics of copper oxide nanoparticles in presence of glyphosate

Recently CuO nanoparticles (n-CuO) have been proposed as an alternative method to deliver a Cu-based pesticide for controlling fungal infestations. With the concomitant use of glyphosate as an herbicide, the interactions between n-CuO and this strong ligand need to be assessed. We investigated the dissolution kinetics of n-CuO and bulk-CuO (b-CuO) particles in the presence of a commercial glyphosate product and compared it to oxalate, a natural ligand present in soil water. We performed experiments at concentration levels representative of the conditions under which n-CuO and glyphosate would be used (∼0.9 mg/L n-CuO and 50 μM of glyphosate). As tenorite (CuO) dissolution kinetics are known to be surface controlled, we determined that at pH 6.5, T ∼ 20 °C, using KNO3 as background electrolyte, the presence of glyphosate leads to a dissolution rate of 9.3 ± 0.7 ×10−3 h−1. In contrast, in absence of glyphosate, and under the same conditions, it is 2 orders of magnitude less: 8.9 ± 3.6 ×10−5 h−1. In a more complex multi-electrolyte aqueous solution the same effect is observed; glyphosate promotes the dissolution rates of n-CuO and b-CuO within the first 10 h of reaction by a factor of ∼2 to ∼15. In the simple KNO3 electrolyte, oxalate leads to dissolution rates of CuO about two times faster than glyphosate. However, the kinetic rates within the first 10 h of reaction are about the same for the two ligands when the reaction takes place in the multi-electrolyte solution as oxalate is mostly bound to Ca2+ and Mg2+.

CuII-Hfur–imidazole] compounds as precursors of efficient hydrogenation and reductive alkylation catalysts in flow systems

The reaction of copper(II) acetate with furoic acids (2Hfur / 3Hfur) and imidazole (Im) in methanol resulted in mononuclear complexes [Cu(fur)2(Im)2(H2O)]·L (fur- = 2fur- (1, 2), 3fur- (3); L = MeCN (1)) whose structures were determined by direct single crystal X-ray analysis. It was found for the first time that copper nanoparticles immobilized on the surface of γ-Al2O3 obtained by chemical reduction of 1, 2 and 3 (pre-deposited on the surface from solution) with sodium tetrahydroborate show high selectivity of mono- and dihydrogenation of tricyclo[5.2.1.02,6]deca-3,8-diene (dicyclopentadiene, DCPD). The catalytic activity tests show a high selectivity (97 %) of the catalyst obtained from an ethanolic solution of complex 1 in the reaction of partial hydrogenation to DHDCPD under continuous process conditions even at high conversion values (up to 96 %) and with an excess of hydrogen, whereas the catalyst obtained from an aqueous solution of complex 1 showed 98 % total hydrogenation product (THDCPD) selectivity. The catalysts based on all the complexes 1–3 were successfully used in reactions of nitrobenzene (NB) reduction to aniline (AN) and in the reductive alkylation of nitrobenzene with isobutanol (i-BAN) 100 % yields of aniline and N-isobutylaniline were obtained at LHSV 0.16 h−1.

Strong plasmon resonance coupling in micro-extraction SERS membrane for in situ detection of molecular aqueous solutions

In situ surface-enhanced Raman scattering (SERS) detection of trace analytes with high sensitivity, especially in complex aqueous solution environments such as polluted water and biological fluids, remains an urgent task. Herein, a micro-extraction SERS membrane was developed by folding a plasmonic structure composing Au@Ag nanoparticles (NPs) and CuO nanospikes (NSs) via capillary action. In the numerical simulation using COMSOL software, we demonstrated that this structure with a parallel facing state can effectively trap and utilize incident photons to excite multiple plasmon resonance couplings. Moreover, it detected the molecular aqueous solution via capillary action in only 5 min. Benefitting from the dense volumetric hotspots and the simple trace extraction solution method, we utilized the proposed membrane for ultrasensitive in situ SERS detections of microcystin–LR (5 ×10–6 μg/L) toxins in drinking water, adenosine biological fluid (10–10 M), and carcinogenic malachite green (10–11 M) in seafood using a portable Raman instrument. The findings of this study provide promising insights for achieving in situ SERS detection of trace analytes in complex aqueous environments.

Cation-Intercalated Lamellar MoS2 Adsorbent Enables Highly Selective Capture of Cesium.

Highly selective capture of cesium (Cs+) from complex aqueous solutions has become increasingly important owing to its (133Cs) indispensable role in some cutting-edge technologies and the environmental mobility of radioactive nuclide (137Cs) from nuclear wastewater. Herein, we report the development of cation-intercalated lamellar MoS2 as an effective Cs+ adsorbent with the advantages of facile synthesis and highly tunable layer spacing. Two types of cations, including Na+ and NH4+, were employed for the intercalations between adjacent layers of MoS2. The results demonstrated that the adsorption capacity of the NH4+-intercalated material (M-NH4+, 134 mg/g) for Cs+ clearly outperformed the others due to higher loading percentages of cations and larger layer spacing. The cesium partition coefficients for M-NH4+ in the presence of 100-fold competing ions all exceed 1 × 103 mL/g. A simulated complex aqueous solution containing 15.37 mg/L Cs+ and highly excess of competing ions Li+, Na+, K+, Mg2+, and Ca2+ (20-306 times higher) was introduced to prove the practical application potential using our best-performing M-NH4+, showing a good to excellent partition ability of Cs+ among other cations, especially for Cs/K and Cs/Na with separation factors of 58 and 212, respectively. The adsorption and selectivity mechanisms were clearly elucidated using various advanced techniques, such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. These results revealed that the good selectivity for Cs+ can be ascribed to the differences in Lewis acidities, hydration energy, cation sizes, and in particular, the divergence of coordination modes which was successfully achieved after tuning the layer distance via the cation intercalation strategy. In addition, the material has fast kinetics (<30 min), wide range of pH tolerance (4-10), and good reusability. Overall, our studies point out that the tunable lamellar MoS2-based materials are promising adsorbents for Cs+ capture and separation.

THEREDA – Thermodynamic Reference Database

Abstract. Part of the process to ensure the safety of radioactive waste disposal is the predictive modeling of the solubility of all relevant toxic components in a complex aqueous solution. To ensure the reliability of thermodynamic equilibrium modeling and to facilitate the comparison of such calculations done by different institutions, it is necessary to create a mutually accepted thermodynamic reference database. To meet this demand, several institutions in Germany joined efforts and created the Thermodynamic Reference Database (THEREDA; Moog et al., 2015). THEREDA is a suite of programs at the base of which resides a relational database. Special emphasis is placed on thermodynamic data along with suitable Pitzer coefficients which allow for the calculation of solubilities in high-saline solutions. Registered users may either download a single thermodynamic datum or ready-to-use parameter files for the geochemical speciation codes PHREEQC, Geochemist's Workbench, CHEMAPP, or TOUGHREACT. Data can also be downloaded in a generic JSON format to allow for import into other codes. The database can be accessed via the world-wide web: http://www.thereda.de (last access: 13 July 2023). Prior to release, the released part of the database is subjected to many tests. Results are compared to results from earlier releases and among the different codes. This is to ensure that, by additions of new and modifications of existing data, no adverse side-effects on calculations are caused. Furthermore, our website offers an increasing number of examples for applications, including graphical representation, which can be filtered by components of the calculated system.

Germanium–Cobalt–Indium Nanostructures as Anodes of Lithium-Ion Batteries for Room- and Low-Temperature Performance

Germanium–cobalt–indium nanostructures were synthesized via cathodic electrodeposition from aqueous complex solutions of Ge (IV) and Co (II) with drop-like indium crystallization centers. This approach features simplicity, avoids heating and allows using cheaper GeO2 instead of pure Ge as starting material. Further, in this case, target nanostructures grow directly upon the substrate. Various analytical methods (scanning electron microscopy, transmission electron microscope and X-ray diffraction) were used for characterization of the nanostructures under study. The samples obtained consist of an array of globular particles of 200 to 800 nm, with nanowires in between. The globules, in turn, contain primary particles of 5 to 10 nm consisting of cobalt, germanium and oxygen. Nanowires consist of germanium and indium. The electrochemical properties of the above-mentioned nanostructures were assessed with cyclic voltammetry and galvanostatic cycling. The germanium–cobalt–indium nanostructures are characterized by a high specific capacity upon lithium insertion, which is approximately 1350 mAh/g at C/8, and a high Coulomb cycling efficiency in the first cycle (approximately 0.76). Germanium–cobalt–indium nanostructures show the ability to operate at high rates up to 16 C at a wide temperature range from +20 to −35 °C.

Three-dimensional Ti3C2 MXene-POSS/V2O3@C nanocomposite aerogel for ultrafast and selective recovery of gold (III) at low temperatures

The scarcity and economic importance of gold has motivated the researchers to develop novel and efficient adsorbents to the increase of recycling from secondary waste streams. In this work, the three-dimensional (3D) Ti3C2 MXene-POSS/V2O3@C aerogel (MPVA) with orderly network structure was fabricated by the interfacial assembly of MXene and freezing-induced preassembly. The new MPVA hybrid exhibited ultrafast kinetics (only 10 min to reach equilibrium), selectivity, and excellent trapping capacity for Au(III), owing to the reductive capture mechanism. The Langmuir model was used to describe the capture of Au(III) delivered by MPVA, achieving the maximum capture capacity of 1425.4 mg g−1 at 298 K. Moreover, MPVA displayed extremely high trapping efficiency (>99.9%) at 273 K, which suggests that this composite is promising for capturing Au(III) in cold temperatures. MPVA also shows good reusability after ten cycles. The results indicate that MPVA has great potential for efficient capturing from complex and cold aqueous solutions.

Encapsulation of antioxidant beta-carotene by cyclodextrin complex electrospun nanofibers: Solubilization and stabilization of beta-carotene by cyclodextrins

Carotenoids act as effective antioxidant defense systems in humans as they scavenge molecular oxygen and peroxyl radicals. However, their poor water solubility and being susceptible to degradation driven by light and oxygen hinder their bioactivity, therefore, they should be stabilized by host matrices against oxidation. Here, β-carotene was encapsulated in electrospun cyclodextrin (CD) nanofibers to increase its water-solubility and photostability to enhance its antioxidant bioactivity. β-carotene/CD complex aqueous solutions were electrospun into nanofibers. The bead-free morphology of the β-carotene/CD nanofibers was confirmed by SEM. The formation of β-carotene/CD complexes was explored through computational modeling and experimentally by FTIR, XRD and solubility tests. The antioxidant activity of the fibers exposed to UV irradiation was demonstrated via a free radical scavenger assay, where β-carotene/CD nanofibers revealed protection against UV radiation. Overall, this work reports the water-borne electrospinning of antioxidant β-carotene/CD inclusion complex nanofibers, which stabilize the encapsulated β-carotene against UV-mediated oxidation.

Specific Ion Effect on the “Water Bridge” Interaction at an Interface: A New Understanding into the Extraction and Separation Selectivity Based upon Competitive Diffusion and Adsorption

Understanding the essence of a specific ion effect on the intermolecular interaction at the near-interface boundary layer during solvent extraction is crucial for developing new approaches to achieve enhanced extraction and separation of various valuable metals from complex aqueous solutions. The present work aims to detect the microscopic effect from competitive diffusion and adsorption of various salt cations in the near-interface boundary layer on their interaction with amphiphilic model molecules, 2-ethylhexylphosphonic acid mono-(2-ethylhexyl) ester (P507), at the air–water interface by using the Langmuir–Blodgett (LB) monolayer technique. It was found that the interaction between cations and P507 molecules through a long-range hydrogen bond “water bridge” confined in the near-interface boundary layer plays a crucial role in determining the difference in the diffusion mass transfer rate of ions with different hydration abilities. Conventional understanding about competitive extraction of various metal cations controlled mainly by their thermodynamic difference in the interaction intensity with the P–O and P═O groups in P507 molecules cannot explain such a kind of specific ion effect on the mass transfer kinetics via ion hydration. Molecular dynamics simulation revealed that the hydration ability of ions is the key factor determining the mass transfer rate and interaction intensity. In the low salt concentration region, the interaction intensity of salt cations with the P–O and P═O groups in P507 molecules is one of the determinants of the competitive adsorption behavior at the interface. However, in a higher salt concentration region, the specific ion salting-out effect via ion hydration becomes significant, causing a decrease in hydration of the target salt cation; therefore, it dominated the diffusion mass transfer rate of ions. This work provides a new insight to understand the kinetic role of competitive diffusion and adsorption of ions in the near-interface boundary layer and their effect on extraction and separation selectivity. It lays the foundation for achieving controllable separation of target metal ions by adjusting the coexisting ion species and their concentrations.

Connecting Diffraction Experiments and Network Analysis Tools for the Study of Hydrogen-Bonded Networks.

A self-consistent scheme is presented that is applicable for revealing details of the microscopic structure of hydrogen-bonded liquids, including the description of the hydrogen-bonded network. The scheme starts with diffraction measurements, followed by molecular dynamics simulations. Computational results are compared with the experimentally accessible information on the structure, which is most frequently the total scattering structure factor. In the case of an at least semiquantitative agreement between experiment and simulation, sets of particle coordinates from the latter may be exploited for revealing nonmeasurable structural details. Calculations of some properties concerning the hydrogen-bonded network are also described, in the order of increasing complexity: starting with the definition of a hydrogen bond, first and second neighborhoods are described via spatial correlations functions. Attention is then turned to cyclic and noncyclic hydrogen-bonded clusters, before cluster size distributions and percolation are discussed. We would like to point out that, as a result of applying the novel protocol, these latter, rather abstract, quantities become consistent with diffraction data: it may thus be argued that the approach reviewed here is the first one that establishes a direct link between measurements and elements of network theories. Applications for liquid water, simple alcohols, and alcohol-water liquid mixtures demonstrate the usefulness of the aforementioned characteristics. The procedure can readily be applied to more complicated hydrogen-bonded networks, like mixtures of polyols (diols, triols, sugars, etc.) and water, and complex aqueous solutions of even larger molecules (even of proteins).

Synergy in Aqueous Systems Containing Bioactive Ingredients of Natural Origin: Saponin/Pectin Mixtures.

Biocompatible and biodegradable ingredients of natural origin are widely used in the design of foam and emulsion systems with various technological applications in the food, cosmetics and pharmaceutical industries. The determination of the precise composition of aqueous solution formulations is a key issue for the achievement of environmentally-friendly disperse systems with controllable properties and reasonable stability. The present work is focused on the investigation of synergistic interactions in aqueous systems containing Quillaja saponins and Apple pectins. Profile analysis tensiometer (PAT-1) is applied to study the surface tension and surface dilational rheology of the adsorption layers at the air/solution interface. The properties and the foam films (drainage kinetics, film thickness, disjoining pressure isotherm, critical pressure of rupture) are investigated using the thin-liquid-film (TLF) microinterferometric method of Scheludko–Exerowa and the TLF-pressure-balance technique (TLF-PBT). The results demonstrate that the structure and stability performance of the complex aqueous solutions can be finely tuned by changing the ratio of the bioactive ingredients. The attained experimental data evidence that the most pronounced synergy effect is registered at a specific saponin:pectin ratio. The obtained information is essential for the further development of aqueous solution formulations intended to achieve stable foams based on mixtures of Quillaja saponins and Apple pectins in view of future industrial, pharmaceutical and biomedical applications.

Insights into High-Performance and Selective Elimination of Cationic Dye from Multicomponent Systems by Using Fe-Based Metal-Organic Frameworks.

Metal-organic frameworks (MOFs), especially Fe-MOFs, have shown prospective application in eliminating organic dyes from wastewater due to their well-developed pores, water stability, easy preparation, and economy. Herein, we synthesized four types of Fe-MOFs (such as MIL-88A, MIL-88B, MIL-100, and MIL-101) using the hydrothermal method. The products were analyzed with several methods. By comparing the adsorption effect of those four types of Fe-MOFs on three kinds of dyes, it has been shown that MIL-100 owns the best adsorption efficiency on cationic organic dyes methylene blue (MB) and Rhodamine B (RhB) in 180 min, while all MOFs have slight removal capacity on methyl orange (MO). MIL-100, as an adsorbent, was studied under various research conditions, and the maximum removal efficiencies to MB, RhB, and MO were found to be up to 97.36%, 88.75%, and 13.00%, respectively. Furthermore, cationic dye MB's removal by MIL-100 was fitted with a pseudo-second-order model and Langmuir isotherm model (Qm = 411.041 mg/g) by adsorption kinetics and isotherms research, and MIL-100 could rapidly and selectively divide MB from a binary complex aqueous solution of MB and MO. The as-fabricated MIL-100 also exhibited excellent recyclability after four adsorption-desorption recycles and can be treated as a potential substance with high removal efficiency of cationic organic dye-containing industrial effluents.

Temperature measurements in the freezing supercooled water droplet by utilizing molecular tagging thermometry technique.

In the present study, we report novel methods to achieve accurate temperature measurements inside the water droplet at its supercooled state as well as during its freezing process. The temperature measurements were based on the molecular tagging thermometry technique. In order to maintain the nonfreezing state of the phosphorescent tracer complex aqueous solution at a subfreezing temperature, a double-layer temperature control container was designed and fabricated. Then, the calibration between the lifetime and temperature of the phosphorescent tracer complex aqueous solution from 7.5 °C to as low as -6.0 °C was carefully performed. Then, the ice fraction (f) was applied to revise the calibration curve for the ice-liquid mixture. The results indicated that the calibration curve for the pure liquid was suitable for the temperature measurements of the pure phosphorescent triplex solution at the supercooling state, while the revised calibration curve for the ice-liquid mixture was appropriate for the temperature measurements in the water droplet during its freezing stage.

Perrhenate recognition within a superphane cavity

In the May issue of <i>Cell Reports Physical Science</i>, Gale and co-workers document a lantern-like receptor (superphane) containing a tailor-made cavity for selective binding of perrhenate anion, leading to an extraordinary capability to separate perrhenate from complex aqueous solutions by either liquid-liquid extraction or solid-phase extraction.