Experimental Study and Numerical Solution of Poly Acrylic Acid Supported Magnetite Nanoparticles Transport in a One-Dimensional Porous Media

M Golzar,M Azhdari Moghaddam,S F Saghravani

doi:10.1155/2014/864068

Abstract

Recently, iron nanoparticles have attracted more attention for groundwater remediation due to its potential to reduce subsurface contaminants such as PCBs, chlorinated solvents, and heavy metals. The magnetic properties of iron nanoparticles cause to attach to each other and form bigger colloid particles of iron nanoparticles with more rapid sedimentation rate in aqueous environment. Using the surfactants such as poly acrylic acid (PAA) prevents iron nanoparticles from forming large flocs that may cause sedimentation and so increases transport distance of the nanoparticles. In this study, the transport of iron oxide nanoparticles (Fe3O4) stabilized with PAA in a one-dimensional porous media (column) was investigated. The slurries with concentrations of 20,100 and 500 (mg/L) were injected into the bottom of the column under hydraulic gradients of 0.125, 0.375, and 0.625. The results obtained from experiments were compared with the results obtained from numerical solution of advection-dispersion equation based on the classical colloid filtration theory (CFT). The experimental and simulated breakthrough curves showed that CFT is able to predict the transport and fate of iron oxide nanoparticles stabilized with PAA (up to concentration 500 ppm) in a porous media.

Highlights

There are various compositions of iron nanoparticles with wide range of applications in environmental engineering, especially in contaminant removal processes
The objective of this study is to investigate the transport of iron oxide nanoparticles (Fe3O4) stabilized with poly acrylic acid (PAA) in one-dimensional porous media
The agglomerate size is a result of the balance between van der Waals forces and magnetic attractions between iron oxide nanoparticles, electrostatic repulsive forces from the adsorbed PAA, and the induced fluid shear in the pore spaces

Summary

Introduction

There are various compositions of iron nanoparticles with wide range of applications in environmental engineering, especially in contaminant removal processes. Observations in laboratory and field scales disclosed the fact that the application of NZVI in porous media faces critical problems including short travel distances, pore plugging, and significant loss of porosity and permeability especially when used in high concentrations [5, 6]. This is attributed to the strong tendency of NZVI bare particles to aggregation, agglomeration, and consequent rapid settlement or filtration on the solid phase surface [7]. To overcome this limitation and to improve NZVI transport in porous media, researchers have used electrostatic, steric, and depletion stabilization mechanisms generating stabilized NZVI colloids by stabilizers like polystyrene sulfonate (PSS), carboxymethyl cellulose (CMC), poly acrylic acid (PAA), triblock, xanthan gum, and emulsified iron [10,11,12,13,14,15]

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