11:20 AM - 11:35 AM
[AHW23-20] Numerical simulations (COMSOL) of γ-Fe2O3 nanohybrids for transport (3D) and arsenic removal in homogeneous porous media
Keywords:Numerical modeling, In-situ arsenic sequestration, Groundwater
To this aim, the γ-Fe2O3 nanohybrids are developed using a novel approach of synthesis which include the usage of industry waste as one of precursor material. These nanoparticles have been found significantly stable in aqueous solutions representing real world groundwater conditions. The measured zeta (ζ)-potential value of -31.6 mV, indicated their significant colloidal stability. In respect to in-situ application, the understanding of transport modeling and retardation of nanomaterials in aquifer systems by simulating through numerical models in complex 3-dimensional scenario are necessary. Therefore, a modeling approach based on modified advection-dispersion-retardation equations has been investigated, considering the coupled influence of head difference and reaction rate of particle transport.
All the experiments were performed in a sand-tank set up (0.6 x 0.3 x 0.50 m) having several injection ports at variable depths. The tank was packed with the porous media (medium size sand) having the grain size (mm), grain density (g cm-3), bulk density (g cm-3) and effective porosity (%) values of 0.5-1.0, 2.33 ±0.2, 1.55 ±0.09 and 0.34 ±0.1, respectively. The longitudinal and traverse dispersivity of consolidated media were calculated using NaCl as a tracer. The COMSOL Multiphysics model (subsurface module) was investigated for simulation of γ-Fe2O3 nanohybrids injection and their transport through porous media. Transport of arsenic and as-synthesized nanomaterial were modelled by considering these as solute and colloid, respectively, under fully saturated homogenous porous media and variable flow rate conditions.
After simulation, the colloidal solution of nanoparticles was allowed to inject at the concentration of 1.25 x 10-4 mol m-3 and flow rate of 1.2 L h-1. The simulation results were matched with the experimental observations which provided estimates of transport parameters. The retardation efficiency utilized to predict the γ-Fe2O3 nanohybrids in similar porous media, although the extend of injection pressure, colloid concentration and pumping rate may be underpredicted which require further investigations.