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The effects of hydrogen bonds on the molecular structure of water-tetrahydrofuran (H2O–THF), water-dimethyl sulfoxide (H2O–DMSO), and water-tetrahydrofuran-dimethyl sulfoxide (H2O–THF–DMSO) in binary aqueous solutions and ternary aqueous solutions were studied using Raman spectroscopy. The results indicate that in the binary aqueous solution, the addition of THF and DMSO will generate hydrogen bonds with water molecules, resulting in changes in the peak positions of S=O bonds and C–O bonds. Compared with the binary aqueous solutions, the hydrogen bonds between DMSO and THF, and the hydrogen bonds between DMSO and H2O in the ternary aqueous solutions are competitive, and the hydrogen bond competition is susceptible to water content. In addition, the formation of hydrogen bonds will destroy the fully hydrogen-bonded water and make it change to the partially hydrogen-bonded water. By fitting the spectra into the three Gaussian components assigned to water molecules with different hydrogen bonding (HB) environments, these spectral features are interpreted by a mechanism that H2O in different solution systems has equal types of water molecules with similar HB degrees-fully hydrogen-bonded H2O (FHW) and partially hydrogen-bonded H2O (PHW). The ratio of the intensity transition from FHW to PHW is determined based on Gaussian fitting. Therefore, the variation of hydrogen bond competition can be supplemented by the intensity ratio of PHW/FHW ((IC2 + IC3)/IC1). This study provides an experimental basis for enriching the hydrogen bonding theory of multivariate aqueous solution systems.

Urea, as a nonelectrolyte molecular solute in aqueous solutions, has a vital role in the thermodynamic, thermophysical and physiochemical studies. To a large extent, addition of Urea to water does not alter the structural dynamics of water. Only a little amount of water molecules is supposed to be closely associated with urea molecules. Therefore, study of intramolecular as well as intermolecular interactions in the binary aqueous urea solution by conducting thermophysical and thermodynamic investigations is quite important. In this work, new experimental data on water activity for solutions containing urea under precisely controlled conditions and derived thermodynamic parameters were reported. Water activity of urea was also estimated from the Kirkwood–Buff integrals in a novel way.

HighlightsAll-aqueous phase approach to membrane fabrication is invented for the first time.Interfacial tension of water-water interface has pronounced effect on the evolution of membrane structures.Covalent organic framework membranes through aqueous two-phase interfacial assembly exhibit high water desalination performances.Aqueous two-phase system features with ultralow interfacial tension and thick interfacial region, affording unique confined space for membrane assembly. Here, for the first time, an aqueous two-phase interfacial assembly method is proposed to fabricate covalent organic framework (COF) membranes. The aqueous solution containing polyethylene glycol and dextran undergoes segregated phase separation into two water-rich phases. By respectively distributing aldehyde and amine monomers into two aqueous phases, a series of COF membranes are fabricated at water–water interface. The resultant membranes exhibit high NaCl rejection of 93.0–93.6% and water permeance reaching 1.7–3.7 L m−2 h−1 bar−1, superior to most water desalination membranes. Interestingly, the interfacial tension is found to have pronounced effect on membrane structures. The appropriate interfacial tension range (0.1–1.0 mN m−1) leads to the tight and intact COF membranes. Furthermore, the method is extended to the fabrication of other COF and metal–organic polymer membranes. This work is the first exploitation of fabricating membranes in all-aqueous system, confering a green and generic method for advanced membrane manufacturing.

Heavy metals are non-biodegradable and carcinogenic pollutants with great bio-accumulation potential. Their ubiquitous occurrence in water and soils has caused serious environmental concerns. Effective strategies that can eliminate the heavy metal pollution are urgently needed. Here the adsorption potential of seven heavy metal cations (Cd2+, Cu2+, Fe3+, Hg2+, Mn2+, Ni2+ and Zn2+) with 20 amino acids was systematically investigated with Density Functional Theory method. The binding energies calculated at B3LYP-D3/def2TZVP level showed that the contribution order of amino acid side chains to the binding affinity was carboxyl > benzene ring > hydroxyl > sulfhydryl > amino group. The affinity order was inversely proportional to the radius and charge transfer of heavy metal cations, approximately following the order of: Ni2+ > Fe3+ > Cu2+ > Hg2+ > Zn2+ > Cd2+ > Mn2+. Compared to the gas-phase in other researches, the water environment has a significant influence on structures and binding energies of the heavy metal and amino acid binary complexes. Collectively, the present results will provide a basis for the design of a chelating agent (e.g., adding carboxyl or a benzene ring) to effectively remove heavy metals from the environment.

In this study, orange peel (OP) biochar was used as a bio-sorbent for the removal of copper and lead from wastewater in single and binary systems. The equilibrium and kinetic studies were conducted at a pH value of 5, which was the maximum adsorption pH value for both metal ions. The equilibrium studies were investigated at a varying initial concentration (10–200 mg/L) with a constant dosage of 0.1 g, while the kinetic studies were conducted at a fixed initial concentration of 200 mg/L with a constant dosage of 1 g/L for both single and binary systems. The maximum adsorption capacity of the orange peel biochar was 28.06 mg/g, 26.83 mg/g, 30.12 mg/g and 27.71 mg/g for single Cu2+, binary Cu2+, single Pb2+ and binary Pb2+ systems, respectively. The Langmuir isotherm model fitted the experimental data, suggesting that adsorption occurred on a monolayer, while the pseudo-second-order model performed well with the kinetic data. The point of zero charge (pHpzc) of the orange peel biochar was found to be 10.03, which revealed that the surface of the bio-sorbent contains basic groups. A Fourier infrared transform (FTIR) spectroscope and scanning electron microscope, coupled with energy dispersive x-ray (SEM-EDX) and x-ray diffraction analyses, were used to determine the functional groups, surface morphology, and inorganic elements present on the surface of the bio-sorbent, respectively. The results obtained have shown that orange peel biochar is efficient for the removal of Cu2+ and Pb2+ ions from an aqueous solution.

Purpose Argan nutshell wood (ANW) has been used in this study as an agricultural solid waste to remove Congo red (CR) from an aqueous solution in single and mixture binary in the presence of methylene blue (MB) or crystal violet (CV). Design/methodology/approach The ANW was characterized by Fourier transform infrared and scanning electron microscope analysis. The effect of ANW dose (8–40 gL−1), contact time (0–180 min), pH of the solution (4–11) and CR dye concentration (100–500 mgL−1) on CR adsorption was studied in batch mode and evaluated by kinetic and isotherm models in a single system. In the binary system, the CR removal was studied from a CR + MB and CR + CV mixture with different percentages of dyes, ranging from 0% to 100%. Findings The pseudo-second-order and the Langmuir models could best describe the CR sorption onto ANW in a single system. In addition, in the case of the binary system, there is the appearance of a synergistic phenomenon between the CR and the other cationic dyes and the CR adsorption capacity increased until 12.24 mg g-1 and 12.06 mg g-1 in the presence of the MB and CV in the mixture, respectively. Practical implications This study demonstrated that ANW prepared can be suggested as an excellent potential adsorbent to remove dyes from wastewaters from single and mixture systems. Originality/value This study is original.

Deep eutectic solvents (DESs) as the novel kind of green solvents have been received widespread attention. After the addition of molecular solvents, a pseudo-binary system is set up with the advantages such as low cost. A kind of DES (1TEAB: 3EG) was prepared and confirmed, and it is mixed with acetonitrile, ethanol and water. Their density, surface tension and refractive index of the DES and its corresponding pseudo-binary mixtures are explored in depth. In addition to the excess molar volumes, the partial molar volumes, partial molar volume at infinite dilution and their excess molar volumes are also investigated. The molar Gibbs free energy and the corresponding molar surface enthalpy could be deduced from the improved Eӧtvӧs equation. It is suggested that the molar Gibbs free energy model is fit for that of DES and its pseudo-binary systems. In addition, the surface tension deviations and refractive index deviations are figured out. This illustrates that there are fairly strong interactions between DES (1TEAB: 3EG) and molecular solvents, which could attribute to mainly two sides: H-bonding and structural effect. Besides, refractive properties such as the molar refraction and free volume are advised that there are ion–dipole interactions between DES and molecular solvents. Graphical abstract

Heavy water is an important industrial chemical for nuclear power generation from natural uranium, precursor for tritium, required for fusion power generation and an important chemical and biochemical tracer. Its separation from natural or synthetic D 2 O–H 2 O binary solutions is highly energy intensive. Therefore for development of chemical and physiochemical processes for its separation, physical properties of binary solutions of D 2 O and H 2 O are important. In this study, density, excess molar volume, refractive indices and related properties are reported for D 2 O–H 2 O binary solutions. Graphical Abstract

Magnesium alloys are widely employed in various applications due to their high strength-to-weight ratio and superior mechanical properties as compared to unalloyed Magnesium. Alloying is considered an important way to enhance the strength of the metal matrix composite but it significantly influences the damping property of pure magnesium, while controlling the rate of corrosion for Mg-based material remains critical in the biological environment. Therefore, it is essential to reinforce the magnesium alloy with a suitable alloying element that improves the mechanical characteristics and resistance to corrosion of Mg-based material. Biocompatibility, biodegradability, lower stress shielding effect, bio-activeness, and non-toxicity are the important parameters for biomedical applications other than mechanical and corrosion properties. The development of various surface modifications is also considered a suitable approach to control the degradation rate of Mg-based materials, making lightweight Mg-based materials highly suitable for biomedical implants. This review article discusses the various binary and ternary Mg alloys, which are mostly composed of Al, Ca, Zn, Mn, and rare earth (RE) elements as well as various non-toxic elements which are Si, Bi, Ag, Ca, Zr, Zn, Mn, Sr, Li, Sn, etc. The effects of these alloying elements on the microstructure, the mechanical characteristics, and the corrosion properties of Mg-based materials were analyzed. The mechanical and corrosion behavior of Mg-based materials depends upon the percentage of elements and the number of alloying elements used in Mg. The outcomes suggested that ZEK100, WE43, and EW62 (Mg-6% Nd-2% Y-0.5% Zr) alloys are effectively used for biomedical applications, having preferable biodegradable, biocompatible, bioactive implant materials with a lower corrosion rate.

The solutal Marangoni effect is attracting increasing interest because of its fundamental role in many isothermal directional transport processes in fluids, including the Marangoni-driven spreading on liquid surfaces or Marangoni convection within a liquid. Here we report a type of continuous Marangoni transport process resulting from Marangoni-driven spreading and Marangoni convection in an aqueous two-phase system. The interaction between a salt (CaCl 2 ) and an anionic surfactant (sodium dodecylbenzenesulfonate) generates surface tension gradients, which drive the transport process. This Marangoni transport consists of the upward transfer of a filament from a droplet located at the bottom of a bulk solution, coiling of the filament near the surface, and formation of Fermat’s spiral patterns on the surface. The bottom-up coiling of the filament, driven by Marangoni convection, may inspire automatic fiber fabrication. In this work, the authors describe a three-dimensional Marangoni transport process in an aqueous two-phase system. Marangoni-driven spreading initiated with salt leads to the formation of Fermat’s spiral patterns, that are of relevance for materials fabrication and microfluidics.