Binary Solutions Research Articles

Integrating binary organic phosphonic acid into nanofiltration membrane for high precision separation of mono-/divalent anions

Nanofiltration membrane (NF) have become increasingly crucial in ion separation. However, traditional polyamide (PA) NF suffers from poor selectivity for mono-/divalent anions due to weak charges and structure defects. Thus, a novel binary organic phosphonic acid, alendronic acid (AA), was firstly used as an aqueous co-monomer via interfacial polymerization (IP) to create negatively charged nanofiltration membranes with both higher charge density and pore size homogeneity for the separation of mono-/divalent anions. Both structure characterization and performance tests demonstrated the successful introduction of AA in the separation layer. Compared with pristine membrane, the NaCl/Na2SO4 selectivity of membrane incorporated with AA was four times improved, while the permeability exhibited no decline. Simultaneously, the separation efficiency of Cl-/SO42- was tested in NaCl/Na2SO4 binary mixed solutions with varying total concentrations and different mass ratios, and the separation factor consistently exceeded 500 across a concentration range of 1 g/L to 20 g/L. Moreover, the AA-integrated membrane exhibited excellent chlorine resistance after 20000 ppm·h of chlorine treatment, which is promising for high efficiency separation of mono-/divalent anions in industrial applications.

Excess properties, intermolecular interactions, and CO2 absorption property of ethylene glycol + diethylenetriamine binary solutions

In this work, the density (ρ) and viscosity (η) data of ethylene glycol (EG) + diethylenetriamine (DETA) binary solutions at T = 298.15 K–318.15 K and P = 100.5 kPa are reported. The basic physicochemical data of binary solutions were used to investigate their excess molar volume (VmE), viscosity deviation (Δη), and excess viscous flow activation Gibbs free energy (ΔG*E), which revealed that there was strong intermolecular interaction in the EG (1) + DETA (2) binary solutions. The density values, viscosity values, and excess properties of binary solutions were fitted by parametric models, such as Jouyban-Acree model, McAllister four-body model, and Redlich-Kister (R-K) equation. After that, the binary solutions were spectroscopically analyzed to further discuss their intermolecular interaction. Meanwhile, Raman, UV, and 1H NMR spectra jointly demonstrated the intermolecular hydrogen bonding of the binary solutions as the form of –OH···N(H2)–. Finally, CO2 absorption was carried out to investigate the CO2 absorption property of the binary solutions, which provided reference data for CO2 capture.

Protein Cryoprotectant Ability of the Aqueous Zwitterionic Solution.

Protein cryopreservation is important for the long-term storage of unstable proteins. Recently, we found that N-acetylglucosaminyltransferase-V (GnT-V) can be cryopreserved in a deep freezer without temperature control using a dilute binary aqueous solution of 3-(1-(2-(2-methoxyethoxy)ethyl)imidazol-3-io)butane-1-carboxylate (OE2imC3C) [10 wt %, mole fraction of solute (x) = 7.75 × 10-3], an artificial zwitterion. However, it is unclear which solvent properties are required in these media to preserve unstable proteins, such as GnT-V. In this study, we investigated the melting phenomena and solution structure of dilute binary aqueous OE2imC3C solutions [x = 0-2.96 × 10-2 (0-30 wt %)] using differential scanning calorimetry (DSC) and Raman and Fourier transform infrared (FTIR) spectroscopies combined with molecular dynamics (MD) simulation to compare the cryoprotectant ability of OE2imC3C with two general cryoprotectants (CPAs), glycerol and dimethyl sulfoxide. DSC results indicated that aqueous OE2imC3C solutions can be melted at lower temperatures with less energy than the control CPA solution, with increasing x, primarily due to OE2imC3C having a higher content of unfrozen water molecules. Moreover, Raman and FTIR results showed that the high content of unfrozen water molecules in aqueous OE2imC3C solutions was due to the hydration around the ionic parts (the COO- group and imidazolium ring) and the OCH2CH2O segment. In addition, the MD simulation results showed that there were fewer structured water molecules around the OCH2CH2O segment than the hydration water molecules around the ionic parts. These solvent properties suggest that dilute aqueous OE2imC3C solutions are effective in preventing freezing, even in a deep freezer. Therefore, this medium has the potential to act as a novel cryoprotectant for proteins in biotechnology and biomedical fields.

Research on coal dust pollution prevention and control based on co-solvent association: Macro-micro experiments and molecular dynamics simulations

In order to better solve the environmental pollution caused by coal dust flying. In this paper, the improvement of wetting and hydrophilicity of coal dust by the binary association solution of surfactant and chelating agent tetrasodium iminodisuccinate (IDS) was studied from the perspective of experiment at the Microcosm–macrocosm analogy levels. To further explore the synergistic mechanism between chelating agents and surfactants, a coal surfactant/chelating agent water three-phase system was constructed using molecular dynamics simulation, and the motion trends of each molecule in different solution systems were analyzed in depth. The combined analysis revealed that sodium dodecylbenzenesulfonate had the best wetting performance when associated with IDS. It increases the surface pores and specific surface area of coal, and the surfactant is more widely adsorbed on the surface of coal dust. The proportion of oxygen-containing hydrophilic groups in coal dust increases, achieving improvement in wetting and hydrophilicity. Overcoming the problem of difficult wetting of coal dust has important practical significance for spray dust reduction and prevention of coal dust pollution.

ULTRASONIC STUDY OF BINARY MIXTURES OF DHMOH AND ACETONE AT 288.15-313.15 K

The density (ρ), viscosity (η), and ultrasonic velocity (u) have been measured in the binary solutions of Dihydromyrcenol (DHMOH) with acetone at different temperatures: 288.15−313.15 K to understand the molecular interaction between these solutions. From the measured values, various acoustical parameters such as adiabatic compressibility (), acoustic impedance (Z), molecular free length (Lf), molar volume (Vm), free volume (Vf), Relative association (RA), internal pressure (i), and molar sound velocity (Um) were determined and correlated with concentration at different temperatures. The observed behaviour of these parameters concerning different compositions is discussed in terms of their molecular interactions between the unlike molecules of the binary solutions. The variations in measured and calculated values with concentration and temperature confirmed the presence of molecular interaction in the mixtures and were further confirmed by relative association.

Non-equilibrium steady states of electrolyte interfaces

The non-equilibrium steady states of a semi-infinite quasi-one-dimensional univalent binary electrolyte solution, characterised by non-vanishing electric currents, are investigated by means of Poisson-Nernst-Planck (PNP) theory. Exact analytical expressions of the electric field, the charge density and the number density are derived, which depend on the electric current density as a parameter. From a non-equilibrium version of the Grahame equation, which relates the total space charge per cross-sectional area and the corresponding contribution of the electric potential drop, the current-dependent differential capacitance of the diffuse layer is derived. In the limit of vanishing electric current these results reduce to those within Gouy-Chapman theory. It is shown that improperly chosen boundary conditions lead to non-equilibrium steady state solutions of the PNP equations with negative ion number densities. A necessary and sufficient criterion on surface conductivity constitutive relations is formulated which allows one to detect such unphysical solutions.

Expression of concern: Kinetic and equilibrium study of graphene and copper oxides modified nanocomposites for metal ions adsorption from binary metal aqueous solution.

Expression of concern: Kinetic and equilibrium study of graphene and copper oxides modified nanocomposites for metal ions adsorption from binary metal aqueous solution.

An isochoric optical platform for interrogation of aqueous glass formation processes.

Aqueous vitrification (glass formation) processes are integral to modern cryopreservation, but experimental methods by which to study them are limited, particularly at the mL volume scales relevant to many biomedical applications. Here, we introduce an inexpensive custom optical platform, the isochoric vitrification cryo-macroscope (or "isovitriscope"), to supplement standard techniques with new qualitative and quantitative data streams. The platform consists of an LED light source, a isochoric (constant-volume) chamber with sapphire optical windows, and a camera, which can operate in two modes. One mode enables sharp visual observation of the glass transition and other low-temperature physical processes, including cracking, annealing, ice and hydrate crystallization, cavity formation, melting, etc. The other mode enables tracking of the optical temperature-evolution of the system via recorded light intensity, which we demonstrate may be used to measure the onset glass transition temperature with accuracy similar to differential scanning calorimetry (DSC), and to identify the temperature coordinates of other phase change events. The isovitriscope thus offers a single device combining the phenomenological insight of conventional visual inspection with the quantitative insight of techniques like calorimetry, at the >1 mL volume scales increasingly relevant to cryopreservation applications. To demonstrate uses of the isochoric optical platform, we herein conduct a series of observational studies examining the rich multi-phase phenomena at play during isochoric vitrification of binary cryoprotectant solutions; the effect of surface wettabilities on crack formation in the glassy state; the analogy between differential calorimetric and optical analysis; and more. In summary, the isochoric vitrification cryo-macroscope, or isovitriscope, adds a valuable new tool for the study of aqueous vitrification processes.

Chemical composition-induced evolution of the structure, domain and electrical properties of Sm-doped (1 - x)Pb(Ni1/3Nb2/3)O3-xPbTiO3.

As the two typical basic binary solid solutions of the relaxor-PbTiO3 family, Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) has been widely investigated, whereas Pb(Ni1/3Nb2/3)O3-PbTiO3 (PNN-PT) has not. Here, 1.5 mol% Sm-doped (1 - x)Pb(Ni1/3Nb2/3)O3-xPbTiO3, (1 - x)PNN-xPT:0.015Sm with x = 0.33-0.39, ceramics have been prepared and the chemical composition-induced evolution of crystal structure, domain, and electrical properties investigated systematically. With increasing PT content, evolution of the rhombohedral-tetragonal structure was observed. A rhombohedral-tetragonal morphotropic phase boundary occurred around x = 0.36-0.37, which showed a peak piezoelectric property with piezoelectric constant d33 = 531 pC N-1 and planar electromechanical coupling factor kp = 0.37 at room temperature. At the same time, the x = 0.36 composition showed improved ferroelectric behavior with remanent polarization Pr = 13.4 μC cm-2 and coercive field Ec = 3.2 kV cm-1. Interestingly, different from its PMN-PT counterpart, there is no temperature-driven phase transition between room temperature and the Curie temperature for (1 - x)PNN-xPT:0.015Sm. These parameters indicated that the PNN-PT system is worthy of more attention and is a promising platform for further development of high-performance piezo/ferroelectric materials.

Efficient Constraint Learning for Data-Driven Active Distribution Network Operation

Scheduling flexible sources to promote the integration of renewable generation is one fundamental problem for operating active distribution networks (ADNs). However, existing works are usually based on power flow models, which require network parameters (e.g., topology and line impedance) that may be unavailable in practice. To address this issue, we propose an efficient constraint learning method to operate ADNs. This method first trains multilayer perceptrons (MLPs) based on historical data to learn the mappings from decisions to constraint violations and power loss. Then, power flow constraints can be replicated by these MLPs without network parameters. We further prove that MLPs learn constraints by formulating a union of disjoint polytopes to approximate the corresponding feasible region. Thus, the proposed method can be interpreted as a piecewise linearization method, which also explains its desirable ability to replicate complex constraints. Finally, a novel pruning method is developed to remove the useless binary variable solutions in advance, which can enhance the solution's reliability and reduce the computational complexity. Numerical experiments based on the IEEE 33- and 123-bus test systems validate that the proposed method can achieve desirable optimality, feasibility, and computational efficiency simultaneously.

ВОДОРАСТВОРИМЫЕ ПРОИЗВОДНЫЕ ЛЕГКИХ ФУЛЛЕРЕНОВ. ОТ ПОСЛЕДОВАТЕЛЬНОЙ ИЕРАРХИЧЕСКОЙ АССОЦИАЦИИ НАНОКЛАСТЕРОВ В ВОДНЫХ РАСТВОРАХ К ЖИДКОСТНОМУ ФАЗООБРАЗОВАНИЮ

The article describes the phenomenon of sequential hierarchical association observed in aqueous solutions of water–soluble derivatives of light fullerenes - C60 and C70 (fullerenols, adducts with carbonic acids, amino acids, low molecular weight proteins) with the general formula CxRn (x = 60, 70; n = 2 ÷ 24; R - substituent). As a result of this process, with an increase in the concentration of monomeric molecules of nanoclusters with linear dimensions of several nm, associates of the I-st order with dimensions of several tens of nm are formed; then associates of the II-nd order with dimensions of the first few hundred nm; then associates of the III-rd order with dimensions of several microns. The formation of type III associates corresponds to the diffusion instability of solutions – a micro-heterogenic state in which there is no delamination of liquid phases in density with a flat interface. Experimental evidence of the effect was obtained using the concentration dependence of excess thermodynamic functions of binary solutions CxRn-H2O obtained by cryometry; data on dynamic light scattering in binary solutions CxRn-H2O; as well as data obtained by studying the topological features of isothermal solubility diagrams of ternary systems of the type: CxRn-Salt-H2O (Salt is an inorganic salt of an alkaline or alkaline–earth s-metal, transition d-metal, lanthanide or actinoid - 4-f, 5-f metal).

Online Ecological Gearshift Strategy via Neural Network with Soft-Argmax Operator

This paper presents a neural network optimizer with soft-argmax operator to achieve an ecological gearshift strategy in real-time. The strategy is reformulated as the mixed-integer model predictive control (MIMPC) problem to minimize energy consumption. Then the outer convexification is introduced to transform integer variables into relaxed binary controls. To approximate binary solutions properly within training, the soft-argmax operator is applied to the neural network with the fact that all the operations of this scheme are differentiable. Moreover, this operator can help push the relaxed binary variables close to 0 or 1. To evaluate the strategy effect, we deployed it to a 2-speed electric vehicle (EV). In contrast to the mature solver Bonmin, our proposed method not only achieves similar energy-saving effects but also significantly reduces the solution time to meet real-time requirements. This results in a notable energy savings of 6.02% compared to the rule-based method.

Spot Overtaking of Dyes of Their Chromatographic Development Associated with Solvent Evaporation.

Infiltration of binary solution of hexane and ethanol into chromatography paper associated with their evaporation was found to generate unexpected initial rapid advancement of wicking front followed by its receding and readvancing in our previous research. In the present study, paper chromatography development of hydrophobic dye, Sudan III, and hydrophilic dye, Acid Blue 9, was carried out using binary solutions of hexane and ethanol in open environment, allowing the developing solvent been evaporated. Sudan III was developed with initial rapid advancing wicking front, while Acid Blue 9 was scarcely developed. On the other hand, Acid Blue 9 was developed with the readvancing second wicking front, while the spot of Sudan III scarcely migrated. Thus, the unexpected illusional phenomenon, overtaking the spot of Sudan III by the spot of Acid Blue 9, was observed. The readvancement of the second wicking front was found to be enhanced as increasing the relative humidity in the environment. Surface temperature of the chromatography paper was measured during the chromatographic development in open environment to show that it became lower than the dew point when the experiments were carried out in relatively high humidity. Solubility of Sudan III in a binary solution of ethanol and water remarkably decreased as increasing the content of water. It was thus suggested that the water vapor condensation to induce water mixing into the mobile phase to decrease the solubility of Sudan III to inhibit its chromatographic development to realize the illusional spot overtaking of dyes of their chromatographic development associated with solvent evaporation.

Surfaces of Atmospheric Droplet Models Probed with Synchrotron XPS on a Liquid Microjet.

ConspectusThe atmosphere is a key part of the earth system comprising myriad chemical species in all basic forms of matter. Ubiquitous nano- and microscopic aerosol particles and cloud droplets suspended in the air play crucial roles in earth's climate and the formation of air pollution. Surfaces are a prominent part of aerosols and droplets, due to the high surface area to bulk volume ratios, but very little is known about their specific properties. Many atmospheric compounds are surface-active, leading to enhanced surface concentrations in aqueous solutions. Their distribution between the surface and bulk may determine heterogeneous chemistry and many other properties of aerosol and cloud droplets, but has not been directly observed.We used X-ray photoelectron spectroscopy (XPS) to obtain direct molecular-level information on the surface composition and structure of aqueous solutions of surface-active organics as model systems for atmospheric aerosol and cloud droplets. XPS is a vacuum-based technique enabled for volatile aqueous organic samples by the application of a high-speed liquid microjet. In combination with brilliant synchrotron X-rays, the chemical specificity of XPS allows distinction between elements in different chemical states and positions within molecular structures. We used core-level C 1s and N 1s signals to identify the alkyl and hydrophilic groups of atmospheric carboxylic acids, alkyl-amines, and their conjugate acids and bases. From this, we infer changes in the orientation of surface-adsorbed species and quantify their relative abundances in the surface. XPS-derived surface enrichments of the organics follow trends expected from their surface activities and we observed a preferential orientation at the surface with the hydrophobic alkyl chains pointing increasingly outward from the solution at higher concentrations. This provides a first direct experimental observation of well-established concepts of surface adsorption and confirms the soundness of the method.We mapped relative abundances of conjugate acid-base pairs in the aqueous solution surfaces from the respective intensities of distinctive XPS signals. For each pair, the protonation equilibrium was significantly shifted toward the neutral form in the surface, compared to the bulk solution, across the full pH range. This represents an apparent shift of the pKa in the surface, which may be toward either higher or lower pH, depending on whether the acid or base form of the pair is the neutral species. The surface shifts are broadly consistent with the relative differences in surface enrichment of the individual acid and base conjugates in binary aqueous solutions, with additional contributions from nonideal interactions in the surface. In aqueous mixtures of surface-active carboxylate anions with ammonium salts at near-neutral pH, we found that the conjugate carboxylic acids were further strongly enhanced. This occurs as the coadsorption of weakly basic carboxylate anions and weakly acidic ammonium cations forms ion-pair surface layers with strongly enhanced local abundances, increasing the probability of net proton transfer according to Le Chatelier's principle. The effect is stronger when the evaporation of ammonia from the surface further contributes to irreversibly perturb the protonation equilibrium, leaving a surplus of carboxylic acid. These surface-specific effects may profoundly influence atmospheric chemistry mediated by aqueous aerosols and cloud droplets but are currently not taken into account in atmospheric models.

Ternary Fe- or Mo-Au-Ni/GDC as Candidate Fuel Electrodes for the Internal Dry Reforming of CH4: Physicochemical and Kinetic Investigation

The present study deals with the physicochemical and catalytic/kinetic investigation of Fe, Au, Fe-Au, and Mo-Au modified Ni/GDC electrocatalysts towards their performance for the DRM, RWGS, and CH4 decomposition reactions. For this purpose, Au-NiO/GDC (where Au = 1 or 3 wt.%), Fe-NiO/GDC (where Fe = 0.5 or 2 wt.%), 0.5Fe-3Au-NiO/GDC, and 0.4Mo-3Au-NiO/GDC were synthesized via deposition (co-) precipitation. There is discussion on the structural properties of the electrocatalysts on the oxidized and reduced state, as well as their use as electrolyte-supported (half) cells. A key remark after H2-reduction is the formation of binary or ternary solid solutions. Ni/GDC was the most active for the catalytic CO2 reforming of CH4 and the CH4 decomposition reactions and as a result the most prone to carbon deposition. On the other hand, the modified 3Au-Ni/GDC, 0.5Fe-3Au-Ni/GDC, and 0.4Mo-3Au-Ni/GDC exhibited the following properties: (i) the highest Ea,app for the non-desired RWGS reaction, (ii) high tolerance to carbon formation due to lower activity for the CH4 decomposition, and (iii) were also less active for H2 and CO production. Finally, 0.4Mo-3Au-Ni/GDC seems to perform the DRM reaction through a different mechanism when compared to Ni/GDC. Overall, the above three samples are proposed as potential fuel electrodes for further electrocatalytic measurements for the SOFC internal DRM process.

Development of a multi-stage model for freezing of a suspended binary solution droplet

The importance of developing spray freeze-drying technology for extending the shelf life of biological and pharmaceutical materials has never been greater, given the increasing food shortage and the strong demand for pharma processes. In particular, the optimal thermal design and application of spray freeze-drying technologies now depend on the estimation of nucleation behavior for droplet solidification (especially the droplets of binary mixtures). Although earlier nucleation models could estimate the nucleation rate and temperature of solidifying droplets, few considered extreme environmental factors, such as extremely low ambient temperatures below −60C∘. To ensure the preservation and storage of biological and pharmaceutical products, such as vaccines and protein drugs, these conditions are essential. Hence, developing an accurate and trustworthy mathematical framework for simulating nucleation is paramount. In this study, a multi-stage, hybrid analytical-numerical model for droplet solidification is developed while coupled with a gradient-based optimization algorithm. Specifically, the five-stage solidification of binary mixtures is simulated (including supercooling of liquid, nucleation, recalescence, equilibrium freezing, and subcooling of solid), which captures the dynamic behaviors of temperature and composition or solute concentration during phase change. The heterogeneous nucleation of a binary-mixture droplet in a frigid environment is predicted and validated against a series of experiments on single suspended droplets at a wide range of ambient temperatures between −20 and −160C∘. The freezing curves of different solute concentrations are also validated against experimental data. It is found that significant variations in interfacial tension lead to abrupt changes in nucleation temperature for extremely cold environments. Further, the effects of the concentration, contact angle, droplet size, and heat transfer coefficient are investigated.

Liquid-Vapor Interface of Aqueous Ethylene Glycol Solutions: A Molecular Dynamics Study.

While the organic constituent in an aqueous binary solution enriches its liquid-vapor (l-v) interface, the extent of enrichment can depend nonlinearly on its mole fraction. A microscopic quantification and rationalization of this behavior are crucial to understand the dependence of properties such as surface tension and evaporation rate of the solution on its composition. Extensive all-atom molecular dynamics simulations of aqueous ethylene glycol (EG) solutions show that the composition of the solution at the l-v interface deviates the most from that in the bulk solution at an EG mole fraction of 0.3. The population of EG molecules with their central C-C dihedral in the gauche conformation was found to be higher at the l-v interface than that in the bulk solution to facilitate the orientation of its hydrophobic methyl groups toward the vapor phase. Free energy calculations reveal that in dilute EG solutions, an EG molecule is most stable at the l-v interface. The behavior of vapor pressure in aqueous EG solutions is ideal and follows Raoult's law, while in contrast, the aqueous solution of dimethyl sulfoxide does not. A rationale for the same is provided through the orientational distribution of interfacial water molecules in the respective solutions.

IBJA: An improved binary DJaya algorithm for feature selection

Feature Selection (FS) is a special preprocessing step in Machine Learning (ML) that reduces the number of unwanted features in datasets to increase the accuracy of ML classifiers. A popular binary variant of the continuous Jaya algorithm is the Discrete Jaya (DJaya) algorithm. It is commonly used for addressing optimization problems with binary design variables (also known as binary decision variables). Nevertheless, DJaya tends to prematurely converge to local optimal solutions, and its performance deteriorates as the complexity of the optimization problem grows. The DJaya algorithm is improved in this article by introducing the Improved Binary DJaya Algorithm (IBJA), which is specially designed to solve the FS problem. IBJA includes three techniques in DJaya. First, it incorporates the update equation of the Harris Hawks Optimization (HHO) algorithm into the optimization loop of DJaya to enhance DJaya’s searching process and exploration abilities. Second, it uses a new Dynamic Opposition-based Learning in the final steps of the optimization loop of DJaya to boost its searching and exploring capabilities. Third, it employs binary transfer functions to calculate binary solutions from the real-valued solutions generated by HHO and DOBL. Using 15 UCI datasets, IBJA’s performance was assessed and compared against four ML classifiers and ten efficient optimization algorithms. Besides, the Friedman statistical test was employed to investigate the reliability of the experimental findings. According to the overall experimental and statistical findings, IBJA scored the highest accuracy, best objective value, and fewest chosen features for each of the 15 UCI datasets.

Conformational Properties of Aβ Peptide Oligomers in Aqueous Ionic Liquid Solution: Insights from Molecular Simulation Studies.

Alzheimer's disease is a progressive irreversible neurological disorder with abnormal extracellular deposition of amyloid β (Aβ) peptides in the brain. We have carried out atomistic molecular dynamics simulations to investigate the size-dependent conformational properties of aggregated Aβ oligomers of different orders, namely, pentamer [O(5)], decamer [O(10)], and hexadecamer [O(16)] in aqueous solutions containing the ionic liquid (IL) 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]). The calculations revealed reduced peptide conformational fluctuations in O(5) and O(10) in the presence of the IL. In contrast, the higher order oligomer [O(16)] has been found to exhibit greater structural distortion due to enhanced flexibilities of its peptide units in the presence of the IL. Based on the distributions of the solvent (water) and the cosolvent (IL) components, it is demonstrated that exchange of water by the IL ion pairs at the exterior surface of the oligomers primarily occurs beyond the first layer of surface-bound water molecules. Importantly, a reduced number of relatively weaker peptide salt bridges have been found in O(16) in binary water-IL solution as compared to the other two smaller-sized oligomers [O(5) and O(10)]. Such differential influence of the IL on peptide salt bridges results in less favorable binding free energies of peptide monomers to O(16), which leads to its greater structural distortion and reduced stability compared to those of O(5) and O(10).

A novel application of HKUST-1 for textile dyes removal in single and binary solutions: Experimental investigation combined with physical modelling

The paper analyzes the single and binary adsorption of textile water pollutants, namely Direct Blue 1 (DB-1) and Direct Yellow-4 (DY-4) dyes, on HKUST-1 at 30 – 50 °C and pH 6.8. Experimental adsorption data indicated that the DB-1 and DY-4 adsorption capacities using this MOF decreased from single to binary systems confirming the presence of a competition effect between these dye molecules on the HKUST-1 adsorbent site. This antagonistic adsorption effect was exothermic. A theoretical approach based on the application of two enhanced adsorption models was utilized to understand the mechanisms for the adsorption of both dye molecules. This approach allowed the calculation of the saturation adsorption capacities for these pollutants in single and binary systems, which followed the next sequence: Qm (DB-1/HKUST-1) > Qm (DY-4/HKUST-1) and Qmb (DB-1 (DB-1 + DY-4)/HKUST-1) > Qmb (DY-4 (DB-1 + DY-4)/HKUST-1). The binary adsorption of these dyes occurred via the presence of an antagonistic effect that reduced the MOF removal performance. HKUST-1 showed better adsorption performance to remove DB-1 dye. The adsorption orientations of DB-1 and DY-4 on HKUST-1 surface were discussed at different temperatures. The models determined the adsorption energies describing the interactions between both dyes and HKUST-1 surface, with range values from 17 to 21 kJ/mol, 12 to 16.5 kJ/mol in single and binary systems respectively. These calculations indicated that physical interactions may trigger the removal of these water pollutants. Overall, this work reports a cutting-edge application of HKUST-1 as adsorbent to remove toxic pollutants such as dye molecules from water.