Pore scale simulation of micro and nanoscale zerovalent iron particles transport

In the field of groundwater remediation, nano and microscale zerovalent iron (NZVI - MZVI) is one of the most promising reagent. It is able to degrade, through redox reactions, recalcitrant and carcinogenic compounds such as perchloroethylene and trichloroethylene. These particles are characterized by a high reactivity and can be injected in the subsurface more easily if compared to the emplacement of granular iron commonly used in permeable reactive barriers (PRBs). Therefore, the characteristics of these particles, their behaviour once injected into the subsoil, their mobility and interactions with the solid matrix of the aquifer must be well known in order to setup an efficient remediation operation. The aim of this study is to analyze the transport of iron micro and nanoparticles and their interaction with the porous media at the microscale, by simulating the capture and deposition of iron particles on the porous matrix. This phenomenon, in fact, is an important mechanism controlling the mobility of colloids in aquifer systems and the effectiveness of the technology. The study was performed by means of numerical simulations of both the flow field and the explicit particles trajectories. The particles transport was simulated with a Lagrangian approach. This gives the possibility to describe accurately the particles trajectories in the flow field and their interaction with the sand grains at the microscale by implementing all the forces acting on them. The basic equation of this approach is the classical Newton’s law. The main aim is to derive a correlation (and to compare it with other correlations found in literature for similar systems) between the parameters characterizing the iron particles, the sand grains and the flow field and the capacity of MZVI and NZVI to cover long distance without be captured from the porous media grains. The resulting correlation will be used for macroscale simulation and future application of a real reclamation activity.