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Impact of Initial Concentration, Adsorbent Dose, and Ionic Strength on Batch Adsorption of Metals and Anions and Elucidation of the Mechanism
Published in Deepak Gusain, Faizal Bux, Batch Adsorption Process of Metals and Anions for Remediation of Contaminated Water, 2021
Deepak Gusain, Shikha Dubey, Yogesh Chandra Sharma, Faizal Bux
The ionic strength influences the thickness and interfacial potential of the double layer, which, in turn, affects the adsorption of the adsorbate. However, the adsorption of copper on multiwalled carbon nanotubes was not affected by ionic strength, as the adsorption is governed by the inner sphere complex formation (Sheng et al. 2010). It is also postulated that the background electrolyte concentration, in turn, affects the ionic strength applied to predict the adsorption. On the basis of the triple-layer model (Hayes and Leckie 1987), β-plane adsorption occurred when ionic strength easily affects the adsorption process; otherwise it follows the o-adsorption process (Sheng et al. 2010). Hence, the adsorption of copper on multiwalled carbon nanotubes participates in o-plane complex reaction. Increase in ionic strength as a result of increasing base in the solution reduced the removal of copper with γ-Al2O3 (Fouladgar et al. 2015). The decrease in Gibbs free energy of the hydrated ion solution is postulated to be the reason for this. It decreases the interaction between the cation in the solution and the adsorbent sites having negative charges, in addition to the promotion of formation M+-OH− ion pairs (Fouladgar et al. 2015). The reduction in removal is also attributed to the competition of positive ions with the adsorbate, screening of electrostatic interaction, and reduction of activity coefficient of copper ions (Hamdaoui 2017).
Fluid–Fluid Dispersions: Liquid–Liquid and Gas–Liquid Systems
Published in Wioletta Podgórska, Multiphase Particulate Systems in Turbulent Flows, 2019
Coalescence is strongly affected by pH (Tobin and Ramkrishna, 1992; Deshiikan and Papadopoulos, 1995a,b; Kraume et al., 2003). When the pH of the aqueous phase deviates from neutral, the tendency of oil drops released from a micropipette to coalesce increases. An increase or decrease in pH results in an increase in the ionic strength of a solution and a decrease in the electrical double-layer thickness. Studies of the independent effects of ionic strength and pH on coalescence suggest that pH is more important than ionic strength in controlling the process.
Filtrative Particle Removal
Published in Maik W. Jornitz, Filtration and Purification in the Biopharmaceutical Industry, 2019
The formation of the electrical double layer and its consequences in terms of charge distributions and the distances over which they hold sway are basic to the understanding of the adsorption mechanism. To recapitulate in the interest of clarity, all surfaces, whether of filters or organisms, etc., acquire a net surface charge of fixed ions when immersed in an aqueous solution (certain to contain ions). This may eventuate from the adsorption of specific ion from the solution, or from the ionic dissociation of functional groups that are part of the surface’s molecular structure. According to Zydney (1996) at neutral pH most microporous membrane surfaces preferentially adsorb negative ions, such as carboxylic acids, and become negatively charged. The carboxylic acid group on a surface is likely to result from the almost inevitable time-dependent oxidation of organic molecules that form parts of the particle or filter surface. Alternatively, positive charges may become adsorbed to become a permanent part of the filter surface.
Colloidal lead in drinking water: Formation, occurrence, and characterization
Published in Critical Reviews in Environmental Science and Technology, 2023
Javier A. Locsin, Kalli M. Hood, Evelyne Doré, Benjamin F. Trueman, Graham A. Gagnon
The impact of ionic strength can be described by DVLO theory. The thickness of the diffuse double layer of a colloid determines its dispersity. The effective thickness of the double layer is directly proportional to the dielectric constant of the solution and zetapotential of the colloid but is inversely proportional to the surface charge density. Consequently, the double layer is thicker when solutions are dilute, resulting in higher colloidal dispersion. Since the dielectric constant is inversely proportional to the electrolyte concentration, the double layer thickness decreases with increasing ionic strength (Napper, 1970). Since most of the studies in the preceding section were carried out in soft waters, the colloidal concentrations can be partly explained by their dispersion due to low ionic strength. In water with higher ionic strength, groundwater for instance, colloidal dispersion would be expected to be lower, allowing more colloids to settle out.
Efficient preparation of phosphazene chitosan derivatives and its applications for the adsorption of molybdenum from spent hydrodesulfurization catalyst
Published in Journal of Dispersion Science and Technology, 2022
Hala. A. Ibrahium, Bahig M. Atia, Nasser. S. Awwad, A. A. Nayl, Hend A. Radwan, Mohamed A. Gado
According to the surface chemistry concept, the solid adsorbent creates an electric double layer with the adsorbate via the electrostatic attraction,[67] which increases the strength of the coexisting ions and compresses double layer thickness.[68] Furthermore, the competition adsorption between these acid anion and Molbdenum anion was thought to be connected to the anion's chemical structure, valence, hydration state, and other factors. The presence of SO42– in solution had a more noticeable influence on the adsorption of Mo (VI). Cl–, a monovalent anion, has lower ion energy and electrostatic adsorption than dianion or trivalent anion. According to the similar reason, SO42– had a stronger competitiveness for binding positively charged surface which weakened the adsorption for Mo(VI).[69,70]
Dispersion stability of nano additives in lubricating oils – an overview of mechanisms, theories and methodologies
Published in Tribology - Materials, Surfaces & Interfaces, 2022
Amir Ashraf, Wani Khalid Shafi, Mir Irfan Ul Haq, Ankush Raina
The steric stabilization is defined as the adsorption of large molecules of adsorbant (surfactant or surface modifying agent) on the surface of nanoparticles in order to prevent aggregation. The increase in the concentration of adsorbed layer on the surface of nanoparticles increases the osmatic repulsive forces which prevents the agglomeration of the nanoparticles. The steric stability of nanoparticles depends upon the concentration on surface, temperature, solubility and average chain length of adsorbed molecules on the nanoparticle surface. In case of steric stability, the surface of nanoparticles is coated with an electric double layer which includes the negatively charged particles on the nanoparticles surface and the positively charged particles on the surface of the film on the surface of nanoparticles the electric double-layer is electrically neutral. The double layer consists of surface charge, stern layer and diffusion layer. According to this theory, the balance of two forces (Van der Waals force and Elastic steric force) establishes the steric stability of nanoparticles [61]. The combination of steric and Van der Waals forces results in the development of the potential well. When the thermal agitation of particles is greater than the combined forces (potential well), the stable dispersion of nanoparticles is obtained in base oil [62].