2 research outputs found
Modeling and Process Design of Intraparticle Adsorption in Single-Stage and Multistage Continuous Stirred Reactors: An Analytical Kinetics Approach
Continuous
adsorption in stirred reactors in the form of carbon
in pulp (CIP) and resin in pulp (RIP) is an established process for
the extraction of gold and uranium. Under the circumstance of intraparticle
diffusion resistance, CIP and RIP have been accurately modeled by
the Boyd’s series (reversible adsorption) and shrinking core
model (irreversible adsorption). The present study, in its first part,
introduces an analytical formula that most closely approximates both
models. Using such formula, the study addresses a basic algorithm
for optimization of single-stage continuous adsorption systems through
linking of the major process variables. Furthermore, this study is
devoted to developing an “analytical kinetics approach”
for the design of multistage CIP and RIP processes via application
of Glauekauf’s multiple series. Advantages of the new approach
over the McCabe–Thiele “Equilibrium Approach”
are (1) the incorporation of the kinetics and equilibrium into one
unified model, and (2) accurate determination of the number of stages,
reactor size, and optimum operational conditions
Comparative Study on Adsorption of Iodine Vapor by Silica-Supported Cu Nanoparticles and Micronized Copper
The current study is aimed at comparison of adsorption
behaviors
of silica-supported Cu nanoparticles (Si–N–Cu) and micrometric
copper powder (Mi-Cu) for uptake of iodine vapor. The Si–N–Cu
was synthesized by the decomposition of aqueous CuÂ(NO<sub>3</sub>)<sub>2</sub> solution at supercritical condition, followed by reduction
of the sample by H<sub>2</sub>–N<sub>2</sub> mixture. The Si–N–Cu
sample with 29.4 nm Cu particles adsorbed 95% of I<sub>2</sub> at
partial pressure 10<sup>–5</sup> bar in 1 h, while the 1 μm
Mi-Cu adsorbed 51% of iodine in 6 h, indicating higher yield and faster
kinetics of the nanometric sample. Theoretical analysis revealed the
existence of a strong thermodynamic size effect in the Cu–I<sub>2</sub> reaction system, so that molar |Δ<i>G</i>| for 2 nm Cu particles was 2.5 times larger than |Δ<i>G</i>| for 1 μm particles. For the Mi-Cu, kinetics obeyed
a three-dimensional diffusion model, while in the case of Si–N–Cu,
diffusion did not play any role in the kinetics. Apparently, no passivation
mechanism was operative in the iodination