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Solubility and Dissolution Rate
Published in Ko Higashitani, Hisao Makino, Shuji Matsusaka, Powder Technology Handbook, 2019
In the measurement of dissolution rates, the Noyes–Whitney equation is often used because it is simple and well supported theoretically by the Nernst consideration with the diffusion layer model, as mentioned above. The change in the amount of solute in a solvent is measured as its concentration at suitable time intervals. Thus, it is convenient that the equation is expressed as the concentration at the time of measurement. By integrating Equation (2.15.12) under the initial condition, C = 0 at t = 0, the equation can be expressed as ln(Cs−C)=−kSt+lnCs
Nanocellulose Application in Encapsulation and Controlled Drug Release
Published in Chetan Keswani, Intellectual Property Issues in Nanotechnology, 2020
Elaine Cristina Lengowski, Eraldo Antonio Bonfatti Júnior, Aline Caldonazo, Kestur Gundappa Satyanarayana
Some factors affect the rate of dissolution, which include surface of the solid, solubility of the solid in the average dissolution, concentration of solute as a function of time and the rate of dissolution constant. Particle size reduction increases the rate of dissolution [70], the characteristic behavior of solid nanoparticles. The drying processes of the solids increase the specific area of the surface and favor the amorphization of the components of the solid formulation, improving the solubility of the dissolution medium [70]. The rate of dissolution is affected under the solute diffusion coefficient and viscosity of the medium, molecular characteristics, and particle size.
Analytical Solutions of the Problem of Mass Transfer with Different Peclet Numbers
Published in G. I. Kelbaliyev, D. B. Tagiyev, S. R. Rasulov, Transport Phenomena in Dispersed Media, 2020
G. I. Kelbaliyev, D. B. Tagiyev, S. R. Rasulov
Dissolution of solids is a process of heterophasic physicochemical interaction of a solid and a liquid, accompanied by the transition of the solid phase into a solution. In contrast to the extraction process, in which the solids contacted with the solution consist of two or more soluble and inert solid phases, the dissolution is selective and is mainly carried out by molecular diffusion.
A Comprehensive Review on Cobalt Bioleaching from Primary and Tailings Sources
Published in Mineral Processing and Extractive Metallurgy Review, 2023
Alex Kwasi Saim, Francis Kwaku Darteh
From kinetics considerations, accelerating the bioleaching rates has been made possible by experiments using a variety of catalysts, including surfactants, metal ions and activated carbon. Indeed, metal ions such as Ag and Cu have greatly increased the bioleaching of Co from sulfide deposits. It is also inferred that low salinity (up to 5 g/L sodium chloride addition) may have a favorable impact on the bioleaching process efficiency (Sadeghieh, Ahmadi, and Hosseini 2020). Surfactants reduce the contact angle between the solution and the mineral and modify the surface properties of the intermediate product, elemental sulfur, improving bacteria elemental sulfur oxidation and Co dissolution rates. For instance, the leaching efficiency of Co was enhanced by around 34% in the presence of surfactants (Tween-20, Tween-80 and RB-1181) (Liu et al. 2015b). The use of a combined catalyst also shows a greater catalytic effect than that of a single catalyst. For example, Co bioleaching efficiency rose by more than 23% when a combined catalyst of Ag+ ions and surfactant was used. In addition, the leaching time was reduced by one quarter (Liu et al. 2018). Similarly, activated carbon and surfactants (Tween-20 and Tween-80) greatly increased the dissolution rate of carrollite, either individually or in combination. The leaching efficiency of Co improved by more than 22% when both activated carbon and surfactant were added, and the leaching time was also reduced by more than 30% (Liu et al. 2015a). However, no literature was found on the use of these catalysts for Co bioleaching from laterite deposits.
Physicochemical factors affecting the mechanical properties of surfactant–polyvinyl alcohol hydrogel
Published in Journal of Dispersion Science and Technology, 2021
Jingying Yu, Hongyuan Wei, Leping Dang
In order to better understand the relationship between PVA–surfactant molecular arrangement and mechanical properties, solubility testing was carried out. As a result, the surfactant–PVA hydrogels with high degrees of crystallization show higher water storage capacities but possess low dissolution rates. Figure 10 shows a comparison of the evaporation rates of SCI/SCG reinforced PVA hydrogels, whereas Figure 11 shows a comparison of dissolution rates. Based on these results, it is clear that the high crystallinity surfactant–PVA systems demonstrate higher water storage capacity of the hydrogel, and correspondingly poor dissolution rates. For surfactants, the most important factor affecting dissolution rates is the arrangement of hydrophilic and hydrophobic groups. Therefore, we could deduce that for different surfactants–PVA hydrogels, the adsorption modes of surfactants on the PVA chain are different.
Preparation, Characterization and ex vivo Intestinal Permeability Studies of Ibuprofen Solid Dispersion
Published in Journal of Dispersion Science and Technology, 2019
Thais Francine Ribeiro Alves, Cecília Torqueti Barros, Denicezar Baldo, Venâncio Alves Amaral, Mirella Sever, Carolina Santos, Patrícia Severino, Marco Vinicius Chaud
The dissolution test is a physical essay able to forecast the amount of drug released and dissolved at a certain time. This process is controlled by the affinity between the solid substance and the solvent, and the mechanism by which this drug is released to dissolution medium. Different factors related to the drug can influence its releases like kind of drug, its polymorphic form, crystallinity, particle size, solubility and its amount in the pharmaceutical dosage form.[38] BU release profile in phosphate buffer (pH 7.2) from SD and PM prepared from Kollicoat IR® and IBU pure are shown in Figure 6. The SD and PM 1:2 (w:w) showed improved dissolution rate over that of IBU pure. At the time of 90 min. the SD sample revealed improved IBU dissolution rate (65,5%) when compared with the PM (31,0%) and IBU pure (13,8%).