Solution Equilibria Research Articles

Enhancement of micro hole wetting and hydrogen bubble release in the process of Ni micro electroforming under megasonic field

Micro hole wetting and hydrogen bubble release are two technical issues in the process of micro hole electroforming. A novel method of megasonic (1.7 MHz) field was introduced in order to solve the two problems and fabricate 20 μm micro column array in this paper. Micro electroforming experiments, capillary tube experiments, electrochemical experiments and testing of contact angle and surface tension coefficient were conducted without and with megasonic field. Experimental results indicated that megasonic field can promote micro hole wetting and bubbles release in the process of micro electroforming. 20 μm micro column array can be fabricated successfully under 2 W/cm2 megasonic field. Because megasonic can decrease the contact angle between photoresist and electroforming solution, reduce the surface tension coefficient of electroforming solution and increase equilibrium potential of nickel. New mechanisms on enhancement of micro hole wetting and bubble release under megasonic field were revealed. The research provides a new comprehension of micro hole wetting and bubble release, which may be good for develop a new method to fabricate micro column array.

Retrieval of zirconium ions from laboratory solutions upon insitu-gel-precipitated aluminium based composite sorbents

Synthesis of innovative substances that serve as potential adsorbents used to reduce pollution impacts or even capture valuable elements is still a target. The strategic point of this work is the preparation of aluminum silicate vanadate nano particles (AlSiV-NPs) and aluminum silicate vanadate tungstate nano particles (AlSiVW-NPs) via the insitu technique. The prepared adsorbents were characterized using FTIR, TGA, TEM, XRD, and SEM-EDX analyses. Studies were conducted on the effects of pH variation, feeding solution concentrations, equilibrium times, and adsorbent weight on the Zr4+ adsorption process on the synthesized adsorbents. With the experimental maximum adsorption capacities of 89 and 95 mg/g for AlSiV-NPs and AlSiVW-NPs, respectively, the equilibrium adsorption results for Zr4+ were in good agreement with the Langmuir isotherm and the qe values were more fitting. The pseudo-second-model kinetically matches both adsorbents suggesting that chemisorption was the approach of adsorption. Thermodynamic results for composites AlSiV-NPs and AlSiVW-NPs show similar values for enthalpy change (−31.5 and −21.08 kJ/mol), entropy change (−47.8 and −7.8 J/mol.. K), and negative free energy change. In summary, Zr4+ adsorption over AlSiV-NPs and AlSiVW-NPs is exothermic, spontaneous, and has a lower degree of disorder. These findings proved the promising future of these composites to recover Zr4+ from aqueous media.

A structure and asymptotic preserving scheme for the Vlasov-Poisson-Fokker-Planck model

We propose a numerical method for the Vlasov-Poisson-Fokker-Planck model written as an hyperbolic system thanks to a spectral decomposition in the basis of Hermite functions with respect to the velocity variable and a structure preserving finite volume scheme for the space variable. On the one hand, we show that this scheme naturally preserves both stationary solutions and linearized free-energy estimate. On the other hand, we adapt previous arguments based on hypocoercivity methods to get quantitative estimates ensuring the exponential relaxation to equilibrium of the discrete solution for the linearized Vlasov-Poisson-Fokker-Planck system, uniformly with respect to both scaling and discretization parameters. Finally, we perform substantial numerical simulations for the nonlinear system to illustrate the efficiency of this approach for a large variety of collisional regimes (plasma echos for weakly collisional regimes and trend to equilibrium for collisional plasmas) and to highlight its robustness (unconditional stability, asymptotic preserving properties).

Development of environmentally-friendly modified bioadsorbents for water treatment

As a result of scientific research, it was found that synthesized pure sorbents based on a composite of Fe3O4 nanoparticles and AlgBT have an increased adsorption capacity due to the inclusion of double hydroxides and an alginate matrix. The processes of complex formation occur according to the principle of maximum inheritance of the structural features of the original coordination compounds, which make it possible to predict and implement the hypothetical structures of new compounds. All this significantly improves the adsorption capacity of the developed adsorbents with respect to phosphate ions. Modified sorbents with a clay basis are therefore a particularly intriguing field. The current research constructed and described modified sorbents, and then conducted tests in the laboratory to determine how well they absorbed phosphate. This study used spectroscopic techniques (SEM, FTIR, X-ray diffraction, and XRD analytical methods) to examine the structure and physicochemical characteristics of improved ecologically friendly sorbents based on alginates, bentonite, and nanoparticles. The alginate core may be physically and chemically modified and can take part in a variety of phosphate anion adsorption methods thanks to the active COOH and OH groups that are present there. The sorption efficiency was established for a modified Fe3O4NPs@AlgBT. Equilibrium in the system sorbent-an aqueous solution of Na2HPO4 is established in 10 hours after the start of sorption, while two-thirds of all sobbed anions pass into the solid phase during the first two hours. The limiting sorption of phosphate ions on modified Fe3O4NPs@AlgBT reaches 410 mg/g, which makes it possible to offer it as an effective sorbent for industrial wastewater treatment

Experimental and theoretical investigations on Hg(II) removal by recyclable composite sorbents comprised of polymers bearing thiourea or amidoxime functional groups and mesoporous silica

It is extremely desirable but still challenging to skilfully manufacture highly efficient sorbents to remmediate, in a reversible manner, the water pollution with mercury. Herein, new sorbents for Hg(II) ions have been designed by the initial synthesis of polyacrylonitrile networks inside mesoporous SiO2 microparticles, followed by the chemical modification of acrylonitrile groups with thiourea or amidoxime moieties. The Hg(II) ions sorption properties of the new composites were compared with respect of initial solution pH, contact time, equilibrium concentration and impact of interfering metal ions. It was demonstrated that the sorbents containing thiourea groups exhibited superior sorption capacities (1.76 mmol Hg(II) g−1) compared to the ones containing amidoxime groups (1.68 mmol Hg(II) g−1), and also higher selectivity for Hg(II) ions separation from binary mixtures with Cu(II), Cd(II) or Pb(II) ions. Kinetic study and DFT results supported a combined sorption mechanism, both physical sorption and chem-isorption being possible. Following the elution of Hg(II) ions with 1 M HNO3 and the regeneration with 0.1 M NaOH, all sorbents exhibited around 90 % sorption capacity recovery after 4 reuse cycles.

Contributions of London Dispersion Forces to Solution-Phase Association Processes.

ConspectusDespite their ubiquity and early discovery, London dispersion forces are often overlooked. This is due, in part, to the difficulty in assessing their contributions to molecular and polymeric structure, stability, properties, and reactivities. However, recent advances in modeling have revealed that dispersion interactions play an important role in many important chemical and biological processes. Experimental confirmation of their impact in solution has been challenging, leading to controversies about their relative importance.In the course of studying noncovalent interactions using molecular devices, our understanding and appreciation for the importance of dispersion interactions have evolved. This Account follows this intellectual journey by using examples from the literature. The goals are twofold: to describe recent advances in understanding the interaction and to provide guidance to researchers studying weak noncovalent interactions. However, first, the experimental methods for measuring the effects of dispersion interactions and the strategies for isolating their influence are described. These include the design of molecular devices to measure these weak noncovalent interactions and the strategies to disentangle the solvation, solvophobic, and dispersion components of the resulting equilibria.The literature examples are organized around five fundamental questions. (1) Do dispersion interactions have a measurable effect on solution equilibria? (2) To what extent do solvents attenuate or compensate for dispersion interactions? (3) To what extent do the solvation and solvophobic terms influence the dispersion equilibria? (4) Can we predict whether a system will form attractive dispersion or repulsive steric interactions? (5) Can the dispersion term be isolated and interrogated? We were often surprised by the answers to these questions. In each case, we describe how the systems were designed to address these questions and discuss possible interpretations of the results.While dispersion interactions in solution were weak (usually <1 kcal/mol), their influence on complexation and conformational equilibria can be observed and measured. This underscores the significance of these interactions in molecular recognition, coordination chemistry, reaction design, and catalysis. The solvent components of the dispersion equilibria can also be significant. Therefore, the isolation of the dispersion contributions from the solvation and solvophobic effects represents an ongoing challenge. The experimental studies also provide important benchmarks and offer valuable insights to help refine the next generation of computational solvent models.

Optimal spatially-dependent diffusion tensors

We consider the spatially-dependent diffusion tensors that maximize the rate of convergence to equilibrium of solutions to the heat equation in inhomogeneous media. We formulate a variational problem for the optimal spectral gap, subject to an Lp constraint on the diffusion tensors, and solve a relaxed version of this variational problem. This provides an upper bound for the optimal spectral gap. The solution is characterized in terms of the extremals of Sobolev and Poincaré type inequalities. To illustrate this result, we give a presentation of the one-dimensional case. In this case, we can adapt the known closed solution of a related eigenvalue problem to write the solution to the relaxed variational problem, arriving at an expression for the upper bound on the optimal spectral gap. The sharpness of this upper bound is then investigated by comparison to numerical simulations.

Neutral Silylyne Complex of Molybdenum: Synthesis, Properties, and Access to Silaiminoacyl Complexes via [2+3] Cycloaddition.

A neutral silylyne complex of molybdenum was synthesized by the stepwise dehydrogenation method and its properties were compared with those of the tungsten analog. The complex takes a dimeric form as crystals but afford a monomer-dimer equilibrium in solution. The replacement of the central metal from W to Mo led to a monomer dominant (~98 %) solution at room temperature. The monomer-dimer dynamics was investigated based on thermodynamic parameters. The molybdenum silylyne complex underwent [2+2] cycloaddition with alkynes much faster than the tungsten analog. The reactions with organic azides led to the formation of the first example of silaiminoacyl complexes through [2+3] cycloaddition. The structures and bonding aspects of the products were clarified by multiple measurements and DFT calculations.

IgY Antibodies from Birds: A Review on Affinity and Avidity.

IgY antibodies are found in the blood and yolk of eggs. Several studies show the feasibility of utilising IgY for immunotherapy and immunodiagnosis. These antibodies have been studied because they fulfil the current needs for reducing, replacing, and improving the use of animals. Affinity and avidity represent the strength of the antigen-antibody interaction and directly influence antibody action. The aim of this review was to examine the factors that influence the affinity and avidity of IgY antibodies and the methodologies used to determine these variables. In birds, there are few studies on the maturation of antibody affinity and avidity, and these studies suggest that the use of an adjuvant-type of antigen, the animal lineage, the number of immunisations, and the time interfered with the affinity and avidity of IgY antibodies. Regarding the methodologies, most studies use chaotropic agents to determine the avidity index. Studies involving the solution phase and equilibrium titration reactions are also described. These results demonstrate the need for the standardisation of methodologies for the determination of affinity and avidity so that further studies can be performed to optimise the production of high avidity IgY antibodies.

A preference for heterolepticity - Schlenk type equilibria in organometallic beryllium systems.

The reactions of beryllium halides with diphenyl beryllium were investigated in the N- and O-donor solvents NEt3 and THF, as well as in benzene and dichloromethane in the presence of the Lewis basic ligands THF, NEt3 and N-heterocyclic carbenes with various steric demand. In all cases the selective formation of heteroleptic beryllium Grignard compounds of the general formula [(L)1-2BePhX]1-2 (X = Cl, Br, I; L = C-, N-, O-donor ligand) was observed. The stability of these complexes was investigated computationally, while the differences between homo- and heteroleptic systems were also evaluated NMR spectroscopically and with single crystal X-ray diffraction. Mechanistic studies on the formation and speciation of these beryllium Grignard complexes in solution were performed.

Development of Stable Amino-Pyrimidine-Curcumin Analogs: Synthesis, Equilibria in Solution, and Potential Anti-Proliferative Activity.

With the clear need for better cancer treatment, naturally occurring molecules represent a powerful inspiration. Recently, curcumin has attracted attention for its pleiotropic anticancer activity in vitro, especially against colorectal and prostate cancer cells. Unfortunately, these encouraging results were disappointing in vivo due to curcumin's low stability and poor bioavailability. To overcome these issues, herein, the synthesis of eight new pyrimidine-curcumin derivatives is reported. The compounds were fully characterized (1H/13C NMR (Nuclear Magnetic Resonance), LC-MS (Liquid Chromatography-Mass Spectrometri), UV-Vis spectroscopy), particularly their acid/base behavior; overall protonation constants were estimated, and species distribution, as a function of pH, was predicted, suggesting that all the compounds are in their neutral form at pH 7.4. All the compounds were extremely stable in simulated physiological media (phosphate-buffered saline and simulated plasma). The compounds were tested in vitro (48 h incubation treatment) to assess their effect on cell viability in prostate cancer (LNCaP and PC3) and colorectal cancer (HT29 and HCT116) cell lines. Two compounds showed the same anti-proliferative activity as curcumin against HCT116 cells and improved cytotoxicity against PC3 cells.

Supramolecular Hybrid Complexes Based on Octahedral Molybdenum(II) Iodide Cluster and Zinc(II) Porphyrin

The possibility of the formation of supramolecular hybrids based on two photosensitizers, an octahedral molybdenum(II) iodide cluster with six terminal isonicotinate ligands (Bu4N)2[{Mo6I8}(OOC–C5H4N)6] (PyMoC, C) and A4-type zinc(II) porphyrin (ZnTPP, P), has been demonstrated. Spectrophotometric and NMR titration methods have shown that the formation of CPn complexes (n = 1–6) occurs in solutions of noncoordinating chlorinated solvents due to the formation of metal–N-ligand coordination bonds between the components. The use of an octahedral cluster as a hexatopic N-ligand and the lability of the Zn···NPy bonds together lead to the formation of a series of CPn complexes (n = 1–6), which are in dynamic equilibrium in solution. Nevertheless, conditions have been selected to isolate single crystals of individual forms CP4 + 2 and CP6 + 2, and their structures have been determined by X-ray diffraction analysis. The PyMoC cluster turns out to coordinate four or six ZnTPP molecules, respectively, while both structures contain two “extramolecules” of zinc(II) porphyrin bound to the cluster via hydrogen bonds involving the oxygen atoms of the isonicotinate groups and protons of water axially coordinated to the porphyrin metal center.

Mixed Solvent Electrolyte Solutions: A Review and Calculations with the eSAFT-VR Mie Equation of State.

In this work, mixed-solvent mean ionic activity coefficients (MIAC), vapor-liquid equilibrium (VLE), and liquid-liquid equilibrium (LLE) of electrolyte solutions have been addressed. An extended literature review of existing electrolyte activity coefficient models (eGE) and electrolyte equations of state (eEoS) for modeling mixed solvent electrolyte systems is first presented, focusing on the details of the models in terms of physical and electrolyte terms, relative static permittivity, and parameterization. The analysis of this literature reveals that the property predictions can be ranked, from the easiest to the most difficult, in the following order: VLE, MIAC, and LLE. We have then used our previously developed eSAFT-VR Mie model to predict MIAC, VLE, and LLE in mixed solvents without fitting any new adjustable parameters. The model was parameterized on MIAC of aqueous electrolyte solutions and successfully extended to nonaqueous, single solvent electrolyte solutions without any new adjustable parameters by using a salt-dependent expression for the relative static permittivity. Our approach yields excellent results for MIAC and VLE of mixed solvent electrolyte solutions, while being fully predictive. LLE is significantly more challenging, and an accurate model for the salt-free solution is crucial for accurate calculations. When the compositions of the two phases in the binary salt-free system are accurately captured, then the electrolyte extension of our model shows a lot of potential and is currently among the best eEoS for LLE prediction in the literature.

Solvent-Dependent Conformational Switching of N-Methyl-N,N'-diarylsquaramide.

N,N'-Diarylsquaramide and N,N'-dialkylsquaramide are conformationally stable linkers with extended (trans, trans) and folded (cis, cis) structures, respectively, independently of external conditions. Here, we show that N-monomethylated N,N'-diarylsquaramides generally take a (trans, cis) structure in the crystal but show a solvent-dependent conformational equilibrium in solution. In particular, the stable conformer of N-methyl-N,N'-bis(1-naphthyl)squaramide (1f) changes depending upon the solvent. Thus, aromatic N-monomethylated squaramides could find application as components of environment-responsive molecular switches.

Experimental Study and Modeling of the Liquid–Liquid and Solid–Liquid–Liquid Equilibrium of Aqueous Solutions Involving 1-Butanol and Xylitol at Different Temperatures

Experimental Study and Modeling of the Liquid–Liquid and Solid–Liquid–Liquid Equilibrium of Aqueous Solutions Involving 1-Butanol and Xylitol at Different Temperatures

Sulfonamido-Pincer Complexes of Cu(II) and the Electrocatalysis of O2 Reduction.

Heteroleptic copper complexes of an asymmetrical pincer ligand containing a central anionic sulfonamide donor (pyridine-2-yl-sulfonyl)(quinolin-8-yl)-amide (psq), which contains a central anionic sulfonamido donor have been prepared. Meridional κ3-N,N″,N‴ binding with the co-ligands acetate, chloride, or acetonitrile (MeCN), trans to the central sulfonamido N-donor, is revealed by the X-ray crystal structures of [Cu(OAc)(psq)(H2O)], [CuCl(psq)]2, and [Cu(psq)(MeCN)](PF6). Either overall distorted square pyramidal or octahedral geometries of the copper atom are satisfied by coordinated water in the case of the acetate complex or interactions with periphery sulfonamido oxygen atoms on adjacent molecules in the dimeric chloride and 1D polymeric acetonitrile complexes. The cyclic voltammogram (CV) of [Cu(OAc)(psq)(H2O)] shows a quasi-reversible CuII/CuI reduction at -0.930 V (vs Fc+/Fc0, MeCN), and an irreversible CuII/CuI reduction for [Cu(psq)(MeCN)](PF6) is seen at -0.838 V. This signal is split into two quasi-reversible redox processes on the addition of 2,2,2-trifluoroethanol (TFE). This suggests that TFE pushes a solution equilibrium toward a dimeric acetate complex analogous to [CuCl(psq)]2, which shows two quasi-reversible waves at -0.666 V and -0.904 V vs Fc+/Fc0 consistent with its dimeric solid-state structure. A comparison of the CVs of [Cu(OAc)(psq)(H2O)] under either a N2 or an O2 atmosphere revealed that this complex catalyzes turnover electro-reduction of O2 to H2O2 and H2O. The rate of reaction increases on addition of a weak organic acid, and a coulombic efficiency of 48% for H2O2 was determined by iodometric titration. We propose that a CuI complex formed on electroreduction binds O2 to yield an intermediate superoxide complex. On electron and proton transfer to this species, a bifurcated route back to the O2-activating CuI complex is feasible with either release of H2O2 or O-O cleavage resulting in the liberation of H2O. The CuI complex is regenerated by subsequent reduction and protonation to close the cycle.

Droplet Evaporation Process of a Fluorobenzene + n-Octane + Polystyrene Mixture.

The vapor-liquid equilibrium of the fluorobenzene-polystyrene binary polymer solution at 303.15 K was measured using a static pressure device. The vapor-liquid equilibrium of the fluorobenzene-n-octane-polystyrene ternary solution in a partial concentration range under normal pressure was determined using an improved Othmer equilibrium still, in which the octane concentration was low. Three activity coefficient models, poly-NRTL, UNIQUAC, and M-UNIQUAC-LBY, were utilized to correlate the experimental data of binary and ternary solutions, and the component activities of the fluorobenzene-n-octane-polystyrene solution at 303.15 K were predicted. A mathematical model based on the Stefan flow was developed to simulate the evaporation process of composite spherical droplets. The activity predicted by the activity coefficient model was used for numerical simulations, and compared with simulations using the activity following Raoult's law. The comparative analysis revealed that simulations based on Raoult's law and activity coefficient models yielded similar results when the mass fraction of fluorobenzene exceeded 0.6. However, in the later stages of evaporation, the calculations based on Raoult's law predicted a 10% shorter drying time for fluorobenzene. The activity coefficient models provided a better approximation and exhibited similar droplet diameter shrinking behaviors to the actual evaporation process.

Leaching toxicity and deformation failure characteristics of phosphogypsum-based cemented paste backfill under chemical solution erosion.

In order to explore the potential environmental and safety risks of phosphogypsum-based cemented paste backfill (PCPB) in mines, aiming at the actual problems of different acidity and alkalinity of the groundwater environment where PCPB is located, the chemical solution erosion test, element concentration determination test, uniaxial compressive strength (UCS) test, and microscopic analysis test of PCPB were carried out. The effects of three different chemical solutions, HCl solution, NaOH solution, and pure water on the leaching toxicity and deformation failure characteristics of PCPB were analyzed. The kinetic equations of pH value of PCPB in the HCl and NaOH solutions, the leaching models of total P and fluoride, and the UCS erosion model of PCPB were established. The research shows that the pH value of PCPB is weak alkaline or alkalinity, when it reaches dynamic equilibrium in different chemical solutions. The leaching concentration of total P is higher than the Class III standard of surface water; the leaching concentration of fluoride is higher than the Class III standard of surface water, the Class III standard of groundwater, and the Class I standard of sewage. In the early stage of chemical solution erosion, scanning electron microscope (SEM) images show that the hydration product C-S-H gel and Aft are intertwined and firmly combined. The research results have important engineering practice and application value in mine environmental governance and safety management.

On a discrete framework of hypocoercivity for kinetic equations

We propose and study a fully discrete finite volume scheme for the linear Vlasov-Fokker-Planck equation written as an hyperbolic system using Hermite polynomials in velocity. This approach naturally preserves the stationary solution and the weighted L 2 L^2 relative entropy. Then, we adapt the arguments developed in Dolbeault, Mouhot, and Schmeiser [Trans. Amer. Math. Soc. 367 (2015), pp. 3807–3828] based on hypocoercivity methods to get quantitative estimates on the convergence to equilibrium of the discrete solution. Finally, we prove that in the diffusive limit, the scheme is asymptotic preserving with respect to both the time variable and the scaling parameter at play.

Pengembangan E-LKPD Berbasis Preview, Question, Read, Reflect, Recite, Review (PQ4R) Pada Materi Kesetimbangan Ion dan pH Larutan Penyangga

The development of PQ4R-based electronic activity sheet on the subject of ionic equilibrium and pH of buffer solutions aims to develop a valid electronic activity sheet and determine user responses in learning. The research method used is the research and development (RD) method by applying a 4D development model which includes Define, Design, Develop and Disseminate, pandemic conditions that cause research to only be carried out until the Develop stage which was followed by one-on-one trials, teacher trials and limited trials. The data collection tools used are validity sheets and user response questionnaires. The data analysis technique used is to calculate the results of the validation assessment and user responses. The results of the study explain that the developed PQ4R-based electronic activity sheet has been categorized as "valid" according to 4 validators based on content, PQ4R characteristics, language, presentation, display, and software utilization with an average score of 96, 88%. One-on-one trials to be applied to 3 students with different abilities to get comments that will be used as improvements to the electronic activity sheet. The results of the user response test for 3 teachers and 20 students were categorized as "very good" with scores of 92.59% and 84.87%, respectively