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 Cu­(NO₃)₂ solution at supercritical condition, followed by reduction of the sample by H₂–N₂ mixture. The Si–N–Cu sample with 29.4 nm Cu particles adsorbed 95% of I₂ at partial pressure 10^–5 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–I₂ 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