Computational Fluid Dynamics Modeling and COMSOL-Based Simulation of Heavy Metal Transport Through a Luffa Cylindrical Packed Bed Reactor for Wastewater Treatment

Abstract

Computational Fluid Dynamics (CFD) modeling offers powerful capabilities for predicting and optimizing adsorption system performance without extensive experimental campaigns. This study presents a comprehensive CFD simulation of Ni(II), Cu(II), and Zn(II) transport through a fixed-bed column packed with nitric acid-treated Luffa cylindrica seeds using COMSOL Multiphysics 6.1. The simulation incorporated the Navier-Stokes equations for fluid flow, the Brinkman equation for porous media hydrodynamics, and the transport of diluted species interface for mass transfer modeling. The two-dimensional axisymmetric geometry represented a 2.5 cm diameter column with 5 cm packed bed height and 0.4 porosity. Model validation against experimental breakthrough data achieved correlation coefficients of 0.8675 for Ni(II), 0.8785 for Cu(II), and 0.9632 for Zn(II), confirming satisfactory predictive capability. The convergence analysis demonstrated stable numerical behavior with error levels below 1 x 10-3. The mean molar mass of the stock solution decreased from 0.0521 to 0.0064 kg/mol through the packed bed, reflecting effective metal removal. Velocity magnitude analysis revealed a rapid decrease from 0.168 m/s at the bed inlet to 0.01293 m/s within 0.42 cm penetration depth, followed by steady-state flow at 0.0112 m/s. The laminar flow regime (Re less than 10) ensured uniform concentration distribution without channeling effects. The validated COMSOL model provides a reliable tool for predicting breakthrough behavior, optimizing operating parameters, and scaling up L. cylindrica packed bed systems for industrial heavy metal wastewater treatment applications, significantly reducing the experimental burden and cost associated with process development.