• Trishikhi Raychoudhury

      Articles written in Journal of Earth System Science

    • Implication of surface modified NZVI particle retention in the porous media: Assessment with the help of 1-D transport model

      Trishikhi Raychoudhury Vikranth Kumar Surasani

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      Retention of surface-modified nanoscale zero-valent iron (NZVI) particles in the porous media near the point of injection has been reported in the recent studies. Retention of excess particles in porous media can alter the media properties. The main objectives of this study are, therefore, to evaluate the effect of particle retention on the porous media properties and its implication on further NZVI particle transport under different flow conditions. To achieve the objectives, a one-dimensional transport model is developed by considering particle deposition, detachment, and straining mechanisms along with the effect of changes in porosity resulting from retention of NZVI particles. Two different flow conditions are considered for simulations. The first is a constant Darcy’s flow rate condition, which assumes a change in porosity, causes a change in pore water velocity and the second, is a constant head condition, which assumes the change in porosity, influence the permeability and hydraulic conductivity (thus Darcy’s flow rate). Overall a rapid decrease in porosity was observed as a result of high particle retention near the injection points resulting in a spatial distribution of deposition rate coefficient. In the case of constant head condition, the spatial distribution of Darcy’s velocities is predicted due to variation in porosity and hydraulic conductivity. The simulation results are compared with the data reported from the field studies; which suggests straining is likely to happen in the real field condition.

    • Transport behaviour of different metal-based nanoparticles through natural sediment in the presence of humic acid and under the groundwater condition


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      The production of nanoparticles (NPs) has increased significantly, given that they have numerous commercial and medical applications. There might have some risk associated with the release of these NPs in the environment. To assess the possible risk of releases of NPs in the groundwater, it is important to evaluate the fate and transport behaviour of NPs through porous media. The objective of this study is, therefore, to evaluate the transport behaviour of widely used NPs [i.e., silver (Ag), iron oxide (Fe$_{\rm{x}}$O$_{\rm{y}}$), titanium dioxide (TiO$_{2}$) and zinc oxide (ZnO)] through porous media in the presence and/or absence of organic matter [i.e., humic acid (HA)] under controlled de-ionized and natural groundwater condition. To achieve the objective, first, the detailed characterizations of NPs are carried out in the presence and absence of HA. Column transport experiments were performed using a 1-D sand-packed column. Different NPs were injected from one end of the column with a flow rate of 0.0054 cm/sec. The result suggests that nAg, nTiO$_{2}$, and nZnO particles are colloidal stable in the suspension, while nFe$_{\rm{x}}$O$_{\rm{y}}$ particles tend to aggregate and settle down very rapidly. However, in the presence of HA, the colloidal stability of nFe$_{\rm{x}}$O$_{\rm{y}}$ in the suspension increases significantly. Evaluation of transport behaviour of different metal NPs suggests that a high amount of nFe$_{\rm{x}}$O$_{\rm{y}}$ (C/C$_{0}$=0.01) and nZnO (C/C$_{0}$=0.09) particles are retained in the porous media. However, in the presence of HA, the transport efficiency of nFe$_{\rm{x}}$O$_{\rm{y}}$ (C/C$_{0}$=0.64) increases significantly. The extensively high amount of nAg and nTiO$_{2}$ particles are transported in the absence/presence of HA. The surface charge of particles and thus the interaction energy between the NPs and the sand is the main factor controlling the deposition of NPs. Overall, it could be stated that there is a risk of migration of nAg and nTiO$_{2}$ particles irrespective of the presence of organic matter or of nFe$_{\rm{x}}$O$_{\rm{y}}$ particles in the presence of organic matter through the aquifer porous media. However, in the natural groundwater system, when the different ion is present, the extent of transport of NPs is expected to be less, and the risk associated with releasing of NPs in the groundwater would be comparatively low than that is predicted under the controlled de-ionized water condition. However, the nTiO$_{2}$ particles always have a high risk of release into the groundwater.

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