Microscale and nanoscale zerovalent iron particles (MZVI and NZVI, respectively), used for groundwater remediation, are not stable when dispersed in water, due to fast aggregation and sedimentation of the particles. Consequently, the use of shear thinning solutions of green biopolymers (e.g. starch, guar gum, xanthan gum) have been recently studied as viscous carrier fluids for the delivery of MZVI and NZVI. Shear thinning fluids exhibit high viscosity at low flow rates (which improves colloidal stability in static conditions) and lower viscosity at high flow rates, corresponding to the injection in the subsurface, when low viscosity (and consequently low pressures) is required. In this work, co-funded by European Union project AQUAREHAB (FP7 - Grant Agreement Nr. 226565), a modelling approach is described to simulate the transport in porous media of nanoscale iron slurries in both laboratory conditions (1-dimensional column tests) and field conditions (radial flow). When modelling the transport of highly concentrated slurries (in the order of several g/l) of NZVI and MZVI in porous media, clogging phenomena (i.e. reduction of porosity and permeability due to particles deposition) are to be taken into account, and the rheological properties of the carrier fluids are to be considered for a correct estimate of pressure drops. Colloid transport mechanisms are controlled by particle-particle and particle-collector interactions, typically modelled with kinetic terms of deposition onto the porous medium and corresponding release. Beside other parameters, deposition and release kinetics are affected by flow rate and fluid viscosity. In this work, column transport tests of microsized iron particles (BASF HQ, d50=1.1 μm) are presented, performed at different flow rates and different polymer concentrations (guar gum at 1.5, 3 and 4 g/l). E-MNM1D is used for inverse simulations of the results, and the dependence of deposition and release kinetics on flow rate and fluid viscosity is modelled. The newly derived relationships are implemented in a radial transport model, E-MNM, which is used for the simulation of field-scale injection of MZVI slurries in porous media. The software is intended as a tool supporting the design of field-scale applications of MZVI and NZVI –based remediation, for the estimate of the radius of influence of the slurry injection.

Micro and nanoscale iron for the remediation of contaminated aquifers: transport tests and modeling / Sethi, Rajandrea; Tosco, TIZIANA ANNA ELISABETTA; Gastone, Francesca; Stekkova, B.. - STAMPA. - (2012), pp. 326-331. (Intervento presentato al convegno Proceeedings of the thirteenth international symposium on environmental issues and waste management in energy and mineral production (SWEMP 2012) tenutosi a Delhi nel November 28-30, 2012).

Micro and nanoscale iron for the remediation of contaminated aquifers: transport tests and modeling

SETHI, RAJANDREA;TOSCO, TIZIANA ANNA ELISABETTA;GASTONE, FRANCESCA;
2012

Abstract

Microscale and nanoscale zerovalent iron particles (MZVI and NZVI, respectively), used for groundwater remediation, are not stable when dispersed in water, due to fast aggregation and sedimentation of the particles. Consequently, the use of shear thinning solutions of green biopolymers (e.g. starch, guar gum, xanthan gum) have been recently studied as viscous carrier fluids for the delivery of MZVI and NZVI. Shear thinning fluids exhibit high viscosity at low flow rates (which improves colloidal stability in static conditions) and lower viscosity at high flow rates, corresponding to the injection in the subsurface, when low viscosity (and consequently low pressures) is required. In this work, co-funded by European Union project AQUAREHAB (FP7 - Grant Agreement Nr. 226565), a modelling approach is described to simulate the transport in porous media of nanoscale iron slurries in both laboratory conditions (1-dimensional column tests) and field conditions (radial flow). When modelling the transport of highly concentrated slurries (in the order of several g/l) of NZVI and MZVI in porous media, clogging phenomena (i.e. reduction of porosity and permeability due to particles deposition) are to be taken into account, and the rheological properties of the carrier fluids are to be considered for a correct estimate of pressure drops. Colloid transport mechanisms are controlled by particle-particle and particle-collector interactions, typically modelled with kinetic terms of deposition onto the porous medium and corresponding release. Beside other parameters, deposition and release kinetics are affected by flow rate and fluid viscosity. In this work, column transport tests of microsized iron particles (BASF HQ, d50=1.1 μm) are presented, performed at different flow rates and different polymer concentrations (guar gum at 1.5, 3 and 4 g/l). E-MNM1D is used for inverse simulations of the results, and the dependence of deposition and release kinetics on flow rate and fluid viscosity is modelled. The newly derived relationships are implemented in a radial transport model, E-MNM, which is used for the simulation of field-scale injection of MZVI slurries in porous media. The software is intended as a tool supporting the design of field-scale applications of MZVI and NZVI –based remediation, for the estimate of the radius of influence of the slurry injection.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11583/2526695
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