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Methane Storage in Nanoporous Carbons
Published in Klaus D. Sattler, st Century Nanoscience – A Handbook, 2020
Iván Cabria, Fabián Suárez-García, Luis F. Mazadiego, Marcelo F. Ortega
As is known, the isotherm obtained experimentally is the excess adsorption isotherm or Gibbs isotherm, i.e., the amount of adsorbed gas whose density is greater than the density of the gas at the same pressure and temperature. Figure 23.1 is a schematic representation of the Gibbs adsorption, where the relation between excess adsorption, absolute adsorbed amount and gas amount compressed in the void space is shown.
Halogen-free COOH functionalized surface-active ionic liquids: surface activity, aggregation behavior, and antimicrobial activity
Published in Journal of Dispersion Science and Technology, 2023
Nidhi N. Patel, Kiran Patel, Nandhibatla V. Sastry, Vaibhav K. Patel, Pradip M. Macwan, Deep S. Sharma, Sanjay. H. Panjabi
Adsorption efficiency values are helpful when comparing the effectiveness of the surfactant's adsorption with the air/water interface. Gibbs isotherm adsorption phenomena were used to estimate the area occupied by a single surfactant molecule at the air-liquid interface (Amin) and Maximum surface excess concentration (Γmax). According to Gibbs Theory, the following equation can be used to determine Γmax.[41] where surface tension is denoted by γ, absolute temperature as T and surfactant concentration is represented by C. Amin can be summed up as:
Monte Carlo simulations probing the liquid/vapour interface of water/hexane mixtures: adsorption thermodynamics, hydrophobic effect, and structural analysis
Published in Molecular Physics, 2018
Mona S. Minkara, Tyler Josephson, Connor L. Venteicher, Jingyi L. Chen, Daniel J. Stein, Cor J. Peters, J. Ilja Siepmann
The Gibbs adsorption isotherm characterises the change in surface tension of an interface as a molecule is adsorbed. For a binary system, the Gibbs isotherm is described by Equation (6), in which the change in surface tension , arises from changes in the surface excess and the chemical potential of each component. Because the n-hexane mole fraction in the liquid film is negligible, the chemical potential of water is essentially constant, leaving only one term in the Gibbs isotherm equation. To evaluate this relationship for the n-hexane/water system, we begin by computing the surface excess, , using Equation (7), where and are the total and excess numbers of n-hexane in the interface box, and are the volumes of vapour and liquid in the regions of the interface box defined according to , and are the densities of n-hexane in the vapour phase reservoir and in the bulk region of the liquid slab (calculated by computing the n-hexane density within the interior 50 Å of the liquid slab), and A is the surface area (multiplied by 2 to account for both interfaces in the simulation box). Numerical values of are compared to the total in Table 2.
Interaction of promethazine hydrochloride with TX-165 in aqueous, NaCl and urea media: a tensiometry and FTIR analysis
Published in Molecular Physics, 2023
M. Alfakeer, Malik Abdul Rub, Naved Azum, Anish Khan, Hadi M. Marwani, Khalid A. Alamry, Abdullah M. Asiri
The diminution of steric and electrostatic repulsion is more operative at air–solution interface in contrast to micelle surface [35]. The adsorption of hydrophobic part of amphiphiles saturates the solution interface causing the surface tension reduction. The portion of amphiphile assimilated per unit of interface at numerous concentrations is quantified through the assistance of the Gibbs adsorption equation. The surface excess concentration () is potent computation of adsorption at the surface. The practicality and minimum area per monomer in Å2 were gauged by applying Equations (5) and (6) [36,37]. where is maximum slope, R =gas constant and NA = Avogadro’s number, and n = total species in bulk phase. The evaluated at interface saturation utilising the Gibbs isotherm, is a quantification of efficacy of the surfactant adsorption, the utmost value that adsorption can accomplish. This feature is of prime importance and finds implementation in emulsification, foaming, wetting, etc. Each evaluated Γmax and value for PMT, TX-165, and PMT + TX-165 mixtures in each solvent are displayed in Table 1. The observed values for mixture given in Table 1 are in between that of pure PMT and surfactant with few exceptions (Table 1). The is transformed into minimum surface area taken by a monomer, through Eq. (12). values of drug-surfactant mixtures in media of aqueous, salt, and urea are greater than Aid (see the values in Table 1) [28]. The Amin value of PMT is greater than that of TX-165 (i.e. Γmax value is more for TX-165 than PMT, because both parameters are inversely proportional to each other), indicating that TX-165 is higher surface active than PMT.