Revealing mass transfer and hydrodynamic effects in a PRDC column by using the integration of extraction and separation
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ORIGINAL PAPER
Revealing mass transfer and hydrodynamic effects in a PRDC column by using the integration of extraction and separation for molybdenum and tungsten ions from aqueous solution Benyamin Shakib1 · Rezvan Torkaman2 · Meisam Torab‑Mostaedi2 · Mehdi Asadollahzadeh2 Received: 3 March 2020 / Accepted: 3 June 2020 © Institute of Chemistry, Slovak Academy of Sciences 2020
Abstract The present work is performed to assess the hydrodynamic parameters and mass transfer coefficients in a PRDC column for the chemical reaction systems. By considering the selective extraction of molybdenum from tungsten, the extraction parameters and synergistic enhancement factor were interpreted at the batch experiments. In the column experiments, the impacts of operating conditions such as the agitation rate, inlet solvent phase velocity as well as inlet aqueous phase velocity were studied on the drop behavior, overall mass transfer coefficients, and extraction efficiencies. The modified correlations by using relationship of dimensionless numbers were illustrated to estimate the hydrodynamic factors (holdup value and the Sauter mean drop diameter) under the physical and reactive systems. The mass transfer coefficients for the continuous phase were evaluated by the axial diffusion method in both extraction and stripping stages. It was observed that the column performance was primarily affected by the agitation speed and mass transfer direction, but this phenomenon slightly changes with the inlet phase velocities. The previous empirical models were compared with the obtained mass transfer data, and the available models were failed to precisely anticipate the experimental data due to chemical reaction conditions. Finally, two new models based on the dimensionless numbers were derived for calculating the overall Sherwood number. The value of separation factor in the extractor indicated the column capacity with the excellent separation for molybdenum from tungsten in the sulfate solution. Keywords Molybdenum and tungsten · PRDC column · Hydrodynamic characteristics · Mass transfer data · Chemical reaction List of symbols AARE Average absolute relative error (-) a Interfacial area (m2/m3) d32 Sauter mean drop diameter (m) D Distribution coefficient (-) Dcol Column diameter (m) Dc Molecular diffusivity of continuous phase (m2/s) DR Disk diameter (m) DS Stator ring diameter (m) * Mehdi Asadollahzadeh [email protected];[email protected]; [email protected] 1
Department of Energy Engineering, Sharif University of Technology, Tehran, 11365‑8639, Iran
Materials and Nuclear Fuel Research School, Nuclear Science and Technology Research Institute, Tehran, P.O. Box: 11365‑8486, Iran
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E Axial mixing coefficient (m2/s) E% Extraction efficiency (-) g Acceleration due to gravity (m/s2) H Effective height of the column (m) hc Compartment height (m) Koc Overall continuous mass transfer coefficient (m/s) Kc Continuous mass transfer coefficient (m/s) Kd Dispersed mass transfer coefficient
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