Nano zero valent iron (nZVI) remediation: A COMSOL modelling approach

ABSTRACT: Remediation using nanoscale zerovalent iron (nZVI) is a promising in situ technology that can convert toxic groundwater contaminants into environment-friendly compounds. Despite its promising characteristics, field scale implementation of nZVI technology has faced major challenges due to poor subsurface mobility, limited longevity and well clogging, all leading to a smaller travel distance. A greater travel distance is preferable since it can reduce the total time of remediation and provide a cost-effective solution. There are several factors that may affect nZVI travel distance such as rapid aggregation, settling, straining, unwanted oxidation, nZVI injection method, pore water velocity, lag phase (time duration when injection of nZVI is stopped), viscosity of solution, concentration of solution and heterogeneity of subsurface. Although various studies have been performed to investigate the effect of some of these parameters, no studies have investigated the role that soil heterogeneity plays on the efficiency of nZVI technology. Such a study may bridge the gap in fundamental understanding of nZVI transport in groundwater and help in overcoming the implementation challenges at the field scale. To examine the possible effects of soil heterogeneity on nZVI transport, a three-dimensional model has been developed using COMSOL, by modifying the colloid filtration theory (CFT) and verified with a previous field validated model.