A Field-Validated Model for In Situ Transport of Polymer-Stabilized nZVI and Implications for Subsurface Injection

Abstract

Nanoscale zerovalent iron (nZVI) particles have significant potential to remediate contaminated source zones. However, the transport of these particles through porous media is not well understood, especially at the field scale. This paper describes the simulation of a field injection of carboxylmethyl cellulose (CMC) stabilized nZVI using a 3D compositional simulator, modified to include colloidal filtration theory (CFT). The model includes composition dependent viscosity and spatially and temporally variable velocity, appropriate for the simulation of push-pull tests (PPTs) with CMC stabilized nZVI. Using only attachment efficiency as a fitting parameter, model results were in good agreement with field observations when spatially variable viscosity effects on collision efficiency were included in the transport modeling. This implies that CFT-modified transport equations can be used to simulate stabilized nZVI field transport. Model results show that an increase in solution viscosity, resulting from injection of CMC stabilized nZVI suspension, affects nZVI mobility by decreasing attachment as well as changing the hydraulics of the system. This effect is especially noticeable with intermittent pumping during PPTs. Results from this study suggest that careful consideration of nZVI suspension formulation is important for optimal delivery of nZVI which can be facilitated with the use of a compositional simulator.

Numerical prediction of diffusion and electric field-induced iron nanoparticle transport

“…[28] to 6-10 m [26], depending on soil characteristics, test operations, and injection velocities [29].…”

The effects of viscosity of carboxymethyl cellulose on aggregation and transport of nanoscale zerovalent iron

“…The relative contribution to deposition due to change in viscosity versus aggregate size change can be determined from Figure 4. Krol et al (2013) have accounted for effect of changes in viscosity with dilution of NZVI suspensions in groundwater following injection in calculations of η 0 towards modeling NZVI transport in aquifers. However, the NZVI aggregate sizes change with viscosity, and this can have an additional impact on estimation of η 0.…”

“…A major hindrance to field-scale implementation of NZVI-based groundwater remediation is the aggregation of NZVI due to the inter-particle magnetic forces (Johnson et al, 2013, Krol et al, 2013. Furthermore, remediation of typical sites via injection of NZVI is expected to require g/L concentrations of NZVI, and at such elevated concentrations there will be extensive aggregation due to the increased likelihood of particleparticle collisions (Raychoudhury et al, 2012).…”

Stabilization of Iron (Micro)Particles with Polyhydroxybutyrate for In Situ Remediation Applications

“…), with the major drawback being the need for their continuous delivery in the groundwater for a lengthy period (long periods are usually required to achieve the remediation goals by using this approach). To overcome these limitations, in recent years, several researchers have shown a growing interest in developing composite materials obtained by the combination of consolidated chemically reactive media with a slow-releasing carbon source (i.e., guar gum, cellulose, starch) to extend treatment to recalcitrant compounds and/or to enhance microbial activity in a synergistic reaction [24][25][26][27]. In this context, polyhydroxybutyrate (PHB) could be a valuable carbon source.…”