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Intermolecular Force Parameters
Published in Mihai V. Putz, New Frontiers in Nanochemistry, 2020
Bogdan Bumbăcilă, Mihai V. Putz
The hydrophobic effect is a manifestation of the non-polar molecules in aqueous solutions. They tend to form aggregates in order to separate from water. This aggregating phenomenon leads to a minimum exposure surface area of the aggregate to the water molecule (Silverman, 2004).
Mechanisms of Particle Removal from Liquid
Published in Maik W. Jornitz, Theodore H. Meltzer, Sterile Filtration, 2020
Maik W. Jornitz, Theodore H. Meltzer
The enclosed nonpolar lipid A core can come into contact with the nonpolar polypropylene pore walls and so become hydrophobically adsorbed upon rupture of the charged hydrophilic pellicle (Fig. 5-9). At the bottom of the hydrophobic effect is the entropically driven tendency of hydrophobic structures to interact with one another in order to reduce their contact with water. The probability of this occurrence is enhanced by a decrease in the pore size of the filter.
Filtrative Particle Removal
Published in Maik W. Jornitz, Filtration and Purification in the Biopharmaceutical Industry, 2019
Robinson et al. (1982) (Figure 5.23) illustrates the LPS (endotoxins) pyrogenic bacterial being adsorptively retained by hydrophobic membranes through the hydrophobic interaction of the uncharged filter surface and the nonpolar lipid A core of the endotoxin. The enclosed nonpolar lipid A core establishes contact with the nonpolar polypropylene pore walls and so becomes hydrophobically adsorbed upon rupture of the charged hydrophilic pellicle. At the bottom of the hydrophobic effect is the entropically driven tendency of hydrophobic structures to interact with one another in order to reduce the area of their contact with water. The probability of this occurrence is enhanced by ultrafilters of lower pore sizes.
Recent progress in adsorptive removal of per- and poly-fluoroalkyl substances (PFAS) from water/wastewater
Published in Critical Reviews in Environmental Science and Technology, 2022
Together with electrostatic interaction, hydrophobic interaction is the main mechanisms for PFAS adsorptive removal. Hydrophobic effect is the pushing of hydrophobic moieties out of the bulk water to interfaces so as to lower the entropy penalty caused by the high ordering of strongly H-bonded water layer around the solute (Shafique et al., 2017). This kind of interaction occurs between the hydrophobic tail of PFAS and hydrophobic surface (of adsorbents and NOM) and is important at high pH values or at negatively charged surfaces where the electrostatic interaction weakens. Many types of adsorbents such as resins and carbonaceous materials conceive hydrophobic interactions as the main interaction mechanism with PFAS; therefore, compounds with sulfonic group and longer chain length are easier to be removed. The increase in hydrophobicity lowers the hydrophilicity of the tail, enhancing an entropy-driven force for the adsorption to the hydrophobic surface; thus, although PFAS are amphiphilic, they tend to be adsorbed on hydrophobic surface rather than staying in the water solution. The hydrophobic interaction helps reduce the effects of coexisting inorganic and nonionic organic in the solution (Conte et al., 2015).
Micellization, surface activities and thermodynamics study of dialkylpyridinium [C16pymCn][Br] (n = 1–4) in aqueous solutions
Published in Journal of Dispersion Science and Technology, 2021
Dong Fu, Xiaoru Gao, Jue Wang, Yang Xie, Fan Yang, Xin Sui, Peng Li, Bo Huang, Xiaochen Zhang, Kan Kan
The decreasing ΔHmθ with temperature shown in Figure 7 results in a negative ΔCp,mθ, which is indicative for the processes where the hydrophobic effect plays an important role. The hydrophobic effect is related to the water removal from the nonpolar surface in order to diminish the extent of less favorable hydrophobic hydration in comparison to clustered water in the bulk. In the case of micellization, water molecules are organized around nonpolar surfactant tails at low temperature (they form an iceberg structure, or their dynamics is slowed down significantly at least). Therefore, the destruction of this water structure is a highly endothermic process.[47] Although, the formation of favorable H-bond in the bulk, ion condensation etc. counteract the endothermic contribution of the hydrophobic dehydration. The results of micellization are a slightly positive overall enthalpy change. In addition, water structure at the hydrophobic surfaces is at least partially disturbed at high temperature. Therefore, the endothermic contribution of the hydrophobic dehydration to the micellization is smaller and ultimately the micellization becomes an exothermic process.
Interfacial properties and micellization of octadecyltrimethylammonium bromide in aqueous solution containing short chain alcohol and effect of chain length of alcohol
Published in Journal of Dispersion Science and Technology, 2020
Dong Mei Li, Jing Huang, Zhao Hua Ren, Ya Jun Lu, Yao Jing He, Shu Wen Liu, Jin Jiang Huang
The micellization of surfactant is attributed mainly to the hydrophobic effect by its nonpolar chain.[34] The alcohol can act as a cosolvent and a structure-breaking solute.[4,12,21] The structure-breaking solute may disturb the ice-like or clathrate-like structure surrounding the hydrophobic chain of surfactant,[35] decreasing the hydrophobic effect considering to be the driving force for the micellization.[4,12,21,38] Then, on adding the alcohol such as MA, EA and PA, the cmc value is larger than in pure water (in Table 1). With the chain length of alcohol, the cmc value decreases, suggesting the depression in the decrease in the hydrophobic effect. In addition, the interaction between the ionic head groups of OTAB should be also considered. In the process of micellization, the electrostatic repulsion between the ionic head group of OTAB is disfavorable to the formation of micelle. It can be explained by the degree of ionization (α) of micelle. The value of α can be obtained by the ratio of the slopes (S1/S2 in Figure 2b) above and below the break indicative of cmc in the plot of the conductivity vs. the concentration of surfactant.[5,39] The data of α in Table 1 show that the α value gradually decreases with the chain length of alcohol, implying the decrease in the electrostatic repulsion of ionic head group in the formation of micelle. With the chain length of alcohol, it is increasingly possible to penetrate into the micelle,[33] including the shell of micelle, consequently decreasing the electrostatic repulsion between ionic head groups. The decrease means a low micelle surface charge density and then a decrease in the dissociation of counterion of ionic head group, namely, a decrease of α. Relatively, for the system containing MA, an excellent solubility induced by MA promote the dissociation of counterion of ionic head group, causing a strong electrostatic interaction between ionic head groups and a high degree of ionization (α) of micelle. Therefore, the strong electrostatic interaction plus the low hydrophobic effect disfavor the process of micellization, all of which result in a large cmc value in the presence of MA.