Title

Elucidating the Mass Transfer Mechanism of CrVI Adsorption by Encapsulated Chitosan-Carbon Nanotubes-Iron Beads in Packed-Bed Columns

Authors

Mian Muhammad Ahson Aslam, Tunghai University
Walter Den, Texas A&M University-San AntonioFollow
Hsion-Wen Kuo, Tunghai University

Document Type

Article

Publication Date

1-25-2022

Abstract

This study evaluates the Cr^VI breakthrough behaviors of a continuous-flow column packed with composite chitosan-MWCNTs‑iron beads under various operating conditions. Under the tested range of experimental parameters, a maximum of 54% of Cr^VI removal was achieved at: water flow rate, 1 mL/min, feed Cr^VI concentration, 30 mg/L; and packed bed height 8 cm. A homogeneous surface diffusion model (HSDM) involving convection-dispersion and diffusion equations was formulated, numerically solved, and experimentally validated. The high degree of conformity between the calculated and experimental breakthrough curves facilitated the determination of mass transfer parameters including axial dispersion D_L, (1.30 × 10⁻⁸ to 1.56 × 10⁻⁷ m²/s) and surface diffusion D_s, (7.28 × 10⁻¹¹ to 1.80 × 10⁻¹⁰ m²/s) via an error minimizing approach. The D_L value was a function of molecular diffusion, which varied with the flow velocity, mass loading, and bed height. The D_s values were slightly higher than those previously reported, owing to the heterogeneous nature of the adsorbent. The external film diffusion coefficient (k_f) was also determined by using Wilson-Geankoplis empirical correlation, which was recognized as a rate-controlling factor during Cr^VI mass transfer to the adsorbent beads. Furthermore, sensitivity analysis showed that a transition from diffuse- to shock-front occurred with a decreasing D_L, while a decrease in the slope of breakthrough curves was observed by decreasing D_s and bed porosity, and increasing k_f and Langmuir parameters. Lastly, the study demonstrated a high correlation between utilization of fractional bed capacity and axial Peclet number. This method is suitable for optimizing operating conditions to maximize the utilization of a fixed-bed columns.

Digital Object Identifier (DOI)

https://doi.org/10.1016/j.jwpe.2022.102586

Comments

This is the author accepted manscript version of:

Aslam, M.M.A., W. Den, H.W. Kuo (2022). “Elucidating the Mass Transfer Mechanism of Cr6+ Adsorption by Encapsulated Chitosan-Carbon Nanotubes-Iron Beads in Packed-Bed Columns,” Journal of Water Processing Engineering 46, 102586.DOI: https://doi.org/10.1016/j.jwpe.2022.102586

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Repository Citation

Aslam, Mian Muhammad Ahson; Den, Walter; and Kuo, Hsion-Wen, "Elucidating the Mass Transfer Mechanism of CrVI Adsorption by Encapsulated Chitosan-Carbon Nanotubes-Iron Beads in Packed-Bed Columns" (2022). Water Resources Science and Technology Faculty Publications. 19.
https://digitalcommons.tamusa.edu/water_faculty/19