Technical Papers and Presentations

Granular and powdered activated carbons have been widely used for purification/filtration in air and water as catalysts or organic adsorbents. To obtain mechanical filtration capacity and inorganic reduction performance, activated carbon can be formed as a block-shaped porous media, demonstrating excellent removal of waterborne contaminants, such as particulate matters, asbestos, cysts, heavy metals as well as various organics and emerging contaminants (Volatile Organic Compounds, Disinfection by-Products, Pharmaceuticals, Endocrine Disrupting Compounds, Perfluorinated Compounds, etc.). To evaluate the performance of adsorbent media, rapid small-scale column test (RSSCT) has been widely used to estimate breakthrough curves of different species in a closed system. However, the RSSCT simulations are based on the ideal plug-flow system in two-dimensional packed bed reactor-shaped structure, and do not articulately represent or estimate system performance of materials in different reactor designs. Especially, simulating both transport and reaction phenomena of each contaminant at the same time is still challenging, since adsorption isotherms of the adsorbents should be simultaneously considered with kinetic parameters determined by the mass balances in the reactor. Total mass in the bulk fluid outside the porous media must be coupled to the mass balances inside the porous media for the aqueous concentration and surface concentrations of the active sites and the surface adsorbed species. Therefore, this case study demonstrates how organic contaminants in a steady-state fluid are dynamically transported in the three-dimensional porous media (activated carbon block) and removed by chemical reaction (adsorption) using COMSOL Multiphysics^® simulation software. First, the fluid movement in the entire reactor is solved in the Free and Porous Media Flow physics interface. Second, the mass transport (advection/diffusion/reaction) of the chemical species in the porous media is modeled with the Transport of Diluted Species in Porous Media interface with a time-dependent study step. The simulation results show the macroscale concentration change over volume treated of each chemical species (more than 5 species total) in the reactor. Illustrations and animated results provide in-depth analysis for time-dependent fluid dynamics for Free and Porous Media Flow, Fluid Pressure, and Particle Trajectories, Transport Study of chemical species. For validation purposes, averaged effluent concentration of organic species compared to actual experimental results. All test methods are followed by NSF/ANSI Protocol 53. The result shows that based on 5% breakthrough line, the 3D COMSOL simulations have only 0.9-2.9% difference, much smaller than classical 2D RSSCT’s 42.0-782.2%. The COMSOL Multiphysics^® model used in this transport/adsorption study successfully demonstrated not only flow patterns in the modulated reactor but also chemical concentration changes in the full-scale porous adsorbent structure. The results are critically important to increase overall usage of adsorbents and to enhance contaminant reduction performance by optimizing design parameters in similar reactor applications. In addition, the transport/adsorption model can be used as a platform estimating the performance of other numerous chemical species and emerging contaminants which have different physical and chemical properties.