A. Mohammadi; J. Moghaddas
Volume 16, Issue 3 , September 2019, , Pages 3-22
Abstract
Although not listed on the United States Pharmacopeia (USP), like standard USP 2, small volume USP 2 dissolution apparatus has gained a great deal of attention, especially for cases where small amount of drug product is available for testing in research and design step or evaluations are to be made on ...
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Although not listed on the United States Pharmacopeia (USP), like standard USP 2, small volume USP 2 dissolution apparatus has gained a great deal of attention, especially for cases where small amount of drug product is available for testing in research and design step or evaluations are to be made on a tablet containing trace amounts of the active pharmaceutical ingredient. In this work, firstly, small volume USP 2 apparatus was designed and manufactured using downscaling rules and considering standard USP 2 as a reference. Then, velocity profile, flow patterns, and shear rate were obtained by PIV and COMSOL simulation software at paddle speeds of 66 and 133 rpm, corresponding to agitation speed of 50 and 100 rpm, respectively, in the standard USP 2. Comparison between experimental and computational results showed acceptable adaptation. Instantaneous velocity data showed eddies and secondary flows in different zones of the vessel, which is desirable for micro-mixing but undesirable in terms of system consistency and reproducibility, as sampling from these zones are known to lead to inconsistent data. Furthermore, increased agitation rate led to the disappearance of rotational zones around the paddle. The magnitude of velocity and shear rate increased by 35% with an increment of paddle stirring from 66 to 133 rpm.
Transport Phenomena,
A. Mohammadi; J. Moghaddas
Volume 16, Issue 1 , March 2019, , Pages 1-21
Abstract
In this study, nanoporous silica aerogel and silica aerogel-activated carbon composites have been synthesized using a water glass precursor by cost effective ambient pressure drying method. Equilibrium and kinetics of benzene and ethyl benzene adsorption on silica aerogel and its composites have been ...
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In this study, nanoporous silica aerogel and silica aerogel-activated carbon composites have been synthesized using a water glass precursor by cost effective ambient pressure drying method. Equilibrium and kinetics of benzene and ethyl benzene adsorption on silica aerogel and its composites have been measured in a batch mode at tree weights of adsorbent. For the first time, the experimental data have been fitted with intra-particle diffusion model for determining of diffusion coefficients. The saturation adsorption capacity of benzene and ethyl benzene vapours was 2033 mg.g-1 and 458 mg.g-1 respectively. The components uptake curves have been described by mathematical models of pseudo first order and pseudo second order models. It has been found that the pseudo first order model fits the experimental data better than the pseudo second order model. Also, the pseudo-second order model could be used for modeling of benzene adsorption over silica aerogel and silica aerogel-2% wt. activated carbon composite at the beginning of adsorption process. The diffusion coefficients of benzene and ethyl benzene within the silica aerogel were in the range of 〖2.16×10〗^(-14) - 〖6.66×10〗^(-13) m2.s-1 and 〖3.65×10〗^(-13) - 〖1.95×10〗^(-12) m2.s-1, respectively.