المؤلفون: Collin, Marie, Prentice, Dale P, Geddes, Dan, Provis, John L, Ellison, Kirk, Balonis, Magdalena, Simonetti, Dante, Sant, Gaurav N

مصطلحات موضوعية: Civil Engineering, Engineering, AFm, equilibrium constant, hydrotalcite, LDH, thermodynamic modeling, Materials Engineering, Mechanical Engineering, Materials, Materials engineering

الوصف: Layered double hydroxide (LDH) phases that form during cement hydration can incorporate a variety of interlayer anions in their interlayer positions. Here, a range of phases of general formula [MII(1−x)MIII(x)(OH)2][An−]x/n·zH2O were synthesized, where MII = Mg2+ (hydrotalcite) or Ca2+ (AFm), MIII = Al3+ such that [MII/Al] = 2 (Ca and Mg, atomic units) or 3 (Mg only), and A = Cl−, Br−, or I−. All the synthesized phases were characterized to assess their composition, density, and crystal structure. By approach from undersaturation, the solubility data of these compounds was measured at 5, 25, and 60°C. This thermochemical data was used to successfully model their formation using thermodynamic modeling and to infer the fields of stability of these compounds for conditions of relevance to cementitious systems. It is seen that halide-containing hydrotalcite phases strongly compete with hydroxide-containing hydrotalcite, with the latter prevailing at high pH. In contrast, halide-containing AFm compounds are more stable compared with hydroxide-containing AFm compositions.

وصف الملف: application/pdf

الوصول الحر: https://escholarship.org/uc/item/0bv6j43pTest

المؤلفون: Haseeb, Abdul, Fernandes, Miguel Xavier, Samuelsson, Jörgen, 1971

المصدر: Journal of Chromatography A. 1730

مصطلحات موضوعية: Adsorption, Adsorption isotherms, Column chromatography, Ionization of liquids, Ionization potential, Liquid chromatography, electrolyte, polypropylene, Adsorption modeling, Charged solutes, Competitive adsorption, Competitive adsorption model, Electrostatic retention model, Elution profiles, Mixed mode, Mixed-mode liquid chromatography, Retention mechanism, Retention modeling, adsorption, algorithm, anion exchange, Article, chromatography, chromatography by stationary phase, column chromatography, elution, equilibrium constant, flow rate, high performance liquid chromatography, ionization, isotherm, pH, retention time (chromatography), reversed phase liquid chromatography, static electricity, ultraviolet irradiation, Electrostatics, Kemi, Chemistry

الوصف: This study investigated the influence of pH on the retention of solutes using a mixed-mode column with carboxyl (-COOH) groups acting as weak cation exchanger bonded to the terminal of C18 ligands (C18-WCX column) and a traditional reversed-phase C18 column. First, a model based on electrostatic theory was derived and successfully used to predict the retention of charged solutes (charged, and ionizable) as a function of mobile phase pH on a C18-WCX column. While the Horváth model predicts the pH-dependent retention of ionizable solutes in reversed-phase liquid chromatography (RPLC) solely based on solute ionization, the developed model incorporates the concept of surface potential generated on the surface of the stationary phase and its variation with pH. To comprehensively understand the adsorption process, adsorption isotherms for these solutes were individually acquired on the C18-WCX and reversed-phase C18 columns. The adsorption isotherms followed the Langmuir model for the uncharged solute and the electrostatically modified Langmuir model for charged solutes. The elution profiles for the single components were calculated from these isotherms using the equilibrium dispersion column model and were found to be in close agreement with the experimental elution profiles. To enable modelling of two-component cases involving charged solute(s), a competitive adsorption isotherm model based on electrostatic theory was derived. This model was later successfully used to calculate the elution profiles of two components for scenarios involving (a) a C18 Column: two charged solutes, (b) a C18 Column: one charged and one uncharged solute, and (c) a C18-WCX Column: two charged solutes. The strong alignment between the experimental and calculated elution profiles in all three scenarios validated the developed competitive adsorption model.

وصف الملف: electronic

الوصول الحر: https://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-100711Test
https://doi.org/10.1016/j.chroma.2024.465058Test
https://kau.diva-portal.org/smash/get/diva2:1878130/FULLTEXT01.pdfTest

المؤلفون: Olga V. Cheremisina, Maria A. Ponomareva, Anastasiya Yu. Molotilova, Yuliya A. Mashukova, Maxim A. Soloviev

المصدر: Записки Горного института, Vol 264, Pp 971-980 (2023)

مصطلحات موضوعية: waste pond, hydrolytic sulphuric acid, sorption, purification, iron (iii), titanium (iv), titanyl, ion exchange, cation exchange resins, equilibrium constant, gibbs energy, environment, Mining engineering. Metallurgy, TN1-997

الوصف: Obtaining and production of metals from natural raw materials causes a large amount of liquid, solid, and gaseous wastes of various hazard classes that have a negative impact on the environment. In the production of titanium dioxide from ilmenite concentrate, hydrolytic sulphuric acid is formed, which includes various metal cations, their main part is iron (III) and titanium (IV) cations. Hydrolytic acid waste is sent to acid storage facilities, which have a high environmental load. The article describes the technology of ion exchange wastewater treatment of acid storage facility from iron (III) and titanium (IV) cations, which form compounds with sulphate ions and components of organic waste in acidic environments. These compounds are subjected to dispersion and dust loss during the evaporation of a water technogenic facility, especially in summer season. Sorption of complex iron (III) cations [FeSO4]+ and titanyl cations TiO2+ from sulphuric acid solutions on cation exchange resins KU-2-8, Puromet MTS9580, and Puromet MTS9560 was studied. Sorption isotherms were obtained both for individual [FeSO4]+ and TiO2+ cations and in the joint presence. The values of the equilibrium constants at a temperature of 298 K and the changes in the Gibbs energy are estimated. The capacitive characteristics of the sorbent were determined for individual cations and in the joint presence.

وصف الملف: electronic resource

العلاقة: https://pmi.spmi.ru/pmi/article/view/15964?setLocale=en_USTest; https://doaj.org/toc/2411-3336Test; https://doaj.org/toc/2541-9404Test

الوصول الحر: https://doaj.org/article/59cb7b18a19741308b9a536401f9a200Test

المؤلفون: Robert Robergs, Bridgette O'Malley, Sam Torrens, Jason Siegler

المصدر: Sports Medicine and Health Science, Vol 5, Iss 4, Pp 336-343 (2023)

مصطلحات موضوعية: Hydrogen ion, Acid, Acidosis, pH, Equilibrium constant (Keq), Ionization, Medicine (General), R5-920

الوصف: The purpose of this review and commentary was to provide an historical and evidence-based account of organic acids and the biochemical and organic chemistry evidence for why cells do not produce metabolites that are acids. The scientific study of acids has a long history dating to the 16th and 17th centuries, and the definition of an acid was proposed in 1884 as a molecule that when in an aqueous solution releases a hydrogen ion (H+). There are three common ionizable functional groups for molecules classified as acids: 1) the carboxyl group, 2) the phosphoryl group and 3) the amine group. The propensity by which a cation will associate or dissociate with a negatively charged atom is quantified by the equilibrium constant (Keq) of the dissociation constant (Kd) of the ionization (Keq ​= ​Kd), which for lactic acid (HLa) vs. lactate (La-) is expressed as: Keq=Kd=[H+][La−][HLa]= 4 677.351 4 (ionic strength ​= ​0.01 Mol⋅L-1, T ​= ​25 ​°C). The negative log10 of the dissociation pKd reveals the pH at which half of the molecules are ionized, which for HLa ​= ​3.67. Thus, knowing the pKd and the pH of the solution at question will reveal the extent of the ionization vs. acidification of molecules that are classified as acids.

وصف الملف: electronic resource

العلاقة: http://www.sciencedirect.com/science/article/pii/S266633762300080XTest; https://doaj.org/toc/2666-3376Test

الوصول الحر: https://doaj.org/article/a940158bff4246c6ae5f3cfce0f14249Test

المؤلفون: Vasily Sergeev, Daniil Balandinsky, Gordey Romanov, Gleb Rukin

المصدر: Arab Journal of Basic and Applied Sciences, Vol 30, Iss 1, Pp 299-306 (2023)

مصطلحات موضوعية: Biochar, chromium, «EcoChar», equilibrium constant, Gibbs energy, wastewater treatment, Science

الوصف: AbstractSorption treatment of wastewater from chromium compounds is a current and actively developing area of research. However, there is a lack of sorbents combining high efficiency and economic affordability with the possibility of application in industrial conditions. In this work, the sorption properties of biochar material “EcoChar,” obtained as a result of fast pyrolysis of agricultural poultry waste, were studied in relation to the removal of trivalent chromium ions, and the basic thermodynamic parameters of the process, which is the type of strong chemisorption, were determined. Based on the IR spectra of the sorbent material, the formation of chelate complexes by hydrolyzed chromium ions with the involvement of carboxylic groups and simple ether bonds is suggested. Using the Langmuir model, the values of sorption capacity of sorbent were found as, 68.8 ± 0,2 mg Cr(III)/g and 87.5 ± 0,3 mg Cr(III)/g at 298 and 318 K, respectively. These values, which are much higher than those of their corresponding waste material counterparts, make the use of this biochar as an adsorbent advantageous for the removal of Cr(III) containing compounds from acidic wastewater.

وصف الملف: electronic resource

العلاقة: https://doaj.org/toc/2576-5299Test

الوصول الحر: https://doaj.org/article/3769566fc597499187977f4837c29a16Test

المؤلفون: Xueyong Zhou, Xin Yu, Rehanguli Maimaitiniyazi, Xiaoying Zhang, Qianwen Qu

المصدر: Heliyon, Vol 10, Iss 8, Pp e28188- (2024)

مصطلحات موضوعية: Thermodynamic parameters, Partition coefficient, Standard adsorption equilibrium constant, Dimension, Spontaneity, Science (General), Q1-390, Social sciences (General), H1-99

الوصف: Accurate calculations and precise results are very important for the dissemination of scientific knowledge, whereas the errors of calculation will diminish the academic value of the paper. This discussion focuses on the calculation of thermodynamics and the determination of the spontaneity of adsorption processes in the paper of Ofudje et al. (2023). Ofudje et al. found that the apatite synthesized by chemical method (CHAp) has excellent adsorption properties for cadmium ions, which is an important contribution to the remediation of cadmium pollution. However, the calculation results of standard Gibbs free energy change (ΔGo), standard enthalpy change (ΔHo) and standard entropy change (ΔSo) of the adsorption of Cd2+ onto CHAp surface need to be corrected due to an incorrect calculation. Firstly, the partition coefficient (KD) with a dimension cannot be used for thermodynamic calculation. Secondly, the adsorbent mass (m) described by Ofudje et al. in different Sections is inconsistent, leading to incorrect results of Ko and ΔGo. When the appropriate value of the adsorbent mass is selected and the partition coefficient is converted to the standard adsorption equilibrium constant Ko, the calculated ΔGo is less than zero, which means that the adsorption is spontaneous. This discussion provides the correct calculation method of standard adsorption equilibrium constants and thermodynamic parameters, which can improve the reader's judgment and understanding of adsorption spontaneity.

وصف الملف: electronic resource

العلاقة: http://www.sciencedirect.com/science/article/pii/S2405844024042191Test; https://doaj.org/toc/2405-8440Test

الوصول الحر: https://doaj.org/article/50a26a84d3fb4b9b80a617763ce4259aTest

المؤلفون: Janina Fischer, Jan Ole Kaufmann, Michael G. Weller

المصدر: Methods and Protocols, Vol 7, Iss 3, p 49 (2024)

مصطلحات موضوعية: ELISA, competitive immunoassay, IC50, test midpoint, point of inflection, equilibrium constant, Biology (General), QH301-705.5

الوصف: The affinity constant, also known as the equilibrium constant, binding constant, equilibrium association constant, or the reciprocal value, the equilibrium dissociation constant (Kd), can be considered as one of the most important characteristics for any antibody–antigen pair. Many methods based on different technologies have been proposed and used to determine this value. However, since a very large number of publications and commercial datasheets do not include this information, significant obstacles in performing such measurements seem to exist. In other cases where such data are reported, the results have often proved to be unreliable. This situation may indicate that most of the technologies available today require a high level of expertise and effort that does not seem to be available in many laboratories. In this paper, we present a simple approach based on standard immunoassay technology that is easy and quick to perform. It relies on the effect that the molar IC50 approaches the Kd value in the case of infinitely small concentrations of the reagent concentrations. A two-dimensional dilution of the reagents leads to an asymptotic convergence to Kd. The approach has some similarity to the well-known checkerboard titration used for the optimization of immunoassays. A well-known antibody against the FLAG peptide, clone M2, was used as a model system and the results were compared with other methods. This approach could be used in any case where a competitive assay is available or can be developed. The determination of an affinity constant should belong to the crucial parameters in any quality control of antibody-related products and assays and should be mandatory in papers using immunochemical protocols.

وصف الملف: electronic resource

العلاقة: https://www.mdpi.com/2409-9279/7/3/49Test; https://doaj.org/toc/2409-9279Test

الوصول الحر: https://doaj.org/article/d885dba7908644e38384070cf124818cTest

المؤلفون: Kumari, Sunita¹, Nunes, André S.¹, Aráujo, Nuno A. M.¹ nmaraujo@fc.ul.pt, da Gama, Margarida M. Telo¹

المصدر: Journal of Chemical Physics. 11/7/2017, Vol. 147 Issue 17, p1-4. 4p. 5 Graphs.

مصطلحات موضوعية: *EQUILIBRIUM constant (Chemistry), *ENERGY harvesting, *BINARY mixtures, *PARTICLE analysis, *DIFFUSION coefficients

مستخلص: Self-propelled active particles are inherently out of equilibrium as they collect energy from their surroundings and transform it into directed motion. A recent theoretical study suggests that binary mixtures of active particles with distinct effective diffusion coefficients exhibit dynamical demixing when their diffusion coefficients differ by more than one order of magnitude. Here, we show that this difference may be reduced drastically in the presence of external fields even when the response to the field is the same for both species. We investigate this demixing as a function of the ratio of the diffusion coefficients and discuss the implications of the results for active systems. [ABSTRACT FROM AUTHOR]

المؤلفون: Dina Kussainova, Athanassios Z. Panagiotopoulos

مصطلحات موضوعية: Biophysics, Microbiology, Immunology, Chemical Sciences not elsewhere classified, technological interest even, present study establishes, observed chemical composition, ab initio <, calculated equilibrium constants, observed partial pressure, gas phase depends, direct coexistence simulations, comparing model predictions, 3 , 2 , relevant experimental measurements, available experimental measurements, observe equilibrium dissociation, overall system sizes, liquid volume ratios, dp model predictions, deep potential model, experimental measurements, deep potential, equilibrium constant, simulations covered, partial pressures, dp model, vapor phase, time scales

الوصف: We developed a first-principles machine learning model for the reactive vapor–liquid phase behavior of molten Li 2 CO 3 . The model was trained on ab initio electronic density functional theory data using the Deep Potential (DP) methodology, and its accuracy was evaluated by comparing model predictions of density and viscosity to experimental measurements. Direct coexistence simulations with the DP model over time scales of tens of nanoseconds were used to observe equilibrium dissociation of Li 2 CO 3 into CO 2 residing primarily in the vapor phase and Li 2 O which remains dissolved in the liquid. The simulations covered a range of temperatures, overall system sizes, and vapor-to-liquid volume ratios. Results were analyzed in terms of the observed chemical composition of the liquid and vapor phases, product structure, and CO 2 partial pressures. In addition, we calculated equilibrium constants for the dissociation reaction by assuming ideal-solution behavior for the liquid. As expected on the basis of thermodynamic arguments and prior experiments for this system, the observed partial pressure of CO 2 in the gas phase depends on both the temperature and the ratio of vapor to liquid volumes, while the calculated equilibrium constants only depend on temperature. DP model predictions for the equilibrium constant of the reaction are generally consistent with the available experimental measurements. The present study establishes the validity of the DP methodology for the description of reactive, multiphase equilibria from first principles, with possible applications to many other systems of scientific and technological interest even in the absence of relevant experimental measurements.

العلاقة: https://figshare.com/articles/journal_contribution/Molecular_Simulation_of_Lithium_Carbonate_Reactive_Vapor_Liquid_Equilibria_Using_a_Deep_Potential_Model/24911154Test

الإتاحة: https://doi.org/10.1021/acs.jced.3c00580.s001Test
https://figshare.com/articles/journal_contribution/Molecular_Simulation_of_Lithium_Carbonate_Reactive_Vapor_Liquid_Equilibria_Using_a_Deep_Potential_Model/24911154Test

المؤلفون: Franzon, Lauri

المساهمون: Department of Chemistry

مصطلحات موضوعية: Transition-state theory, Ab-initio, Equilibrium-constant, Spectroscopy, Dynamics, Energy, Water, Thermodynamics, Products, Kinetics, 116 Chemical sciences

الوصف: In this article, we propose a simple method of estimatingdissociationrates of bimolecular van der Waals complexes ("wells"),rooted in rigid body dynamics, requiring as input parameters onlythe bimolecular binding energy, together with the intermolecular equilibriumdistance and moments of inertia of the complex. The classical equationsof motion are solved for the intermolecular and rotational degreesof freedom in a coordinate system considering only the relative motionof the two molecules, thus bypassing the question of whether the energyof the complex is statistically distributed. Well-escaping trajectoriesare modeled from these equations, and the escape rate as a functionof relative velocity and angular momentum is fitted to an empiricalfunction, which is then integrated over a probability distributionof said quantities. By necessity, this approach makes crude assumptionson the shape of the potential well and neglects the impact of energyquantization, and, more crucially, the coupling between the degreesof freedom included in the equations of motion with those that arenot. We quantify the error caused by the first assumption by comparingour model potential with a quantum chemical potential energy surface(PES) and show that while the model does make several compromisesand may not be accurate for all classes of bimolecular complexes,it is able to produce physically consistent dissociation rate coefficientswithin typical atmospheric chemistry confidence intervals for tripletstate alkoxyl radical complexes, for which the detailed balance approachhas been shown to fail. ; Peer reviewed

وصف الملف: application/pdf

العلاقة: Franzon , L 2023 , ' Simple Physical Model for the Estimation of Irreversible Dissociation Rates for Bimolecular Complexes ' , Journal of Physical Chemistry A , vol. 127 , no. 28 , pp. 5956-5966 . https://doi.org/10.1021/acs.jpca.3c01890Test; 98fc97bb-7ebc-4fbf-a6eb-3d46a3ee9711; http://hdl.handle.net/10138/572681Test; 001022341200001

الإتاحة: https://doi.org/10.1021/acs.jpca.3c01890Test
http://hdl.handle.net/10138/572681Test