Exploring the deposition mechanism in saturated porous media for polydisperse composites of XG and nZVI@rGO

Engineered nanomaterials (ENMs) have shown promise for remediation of groundwater contaminants and the potential application relies on the delivery of aqueous solutions of ENMs to a targeted subsurface location or region. Thus, the ability to accurately predict nanoparticle transport and retention in saturated porous media is one of the most technical challenges faced by the design and assessment of potential field-scale environmental applications. Here, a prior prediction model was presented by coupling the effect of Derjaguine-Landaue-Verweye-Overbeek (DLVO) interaction, Brownian diffusion, hydrodynamics and interception. Characteristics used in the model were medium size, porosity, injection velocity, size distribution of particles, attachment efficiency, single-collector contact efficiency. The direct comparison of parameterized prior model predictions to experimental measurements was proposed to thoroughly understand deposition mechanism of polydisperse ENM. The model predicted deposition rate coefficient quantitatively very close to measured rates. When the particle diameter (d_p) of ENM excessed 1.2080 mm, it was retained in the porous medium by interception; When d_p < 0.1737 mm, ENM would deposite in the porous medium if the kinetic energy (E_k) it possessed is less than the depth of the secondary energy minimum; When 0.1737 mm < d_p < 1.2080 mm, deposition occurred where adhesive torques (T_A) was in excess of hydrodynamic drag torgues (T_H) particles subject to. Further, deposition rate was positive correlated with injection concentrations among the range of 0.34 g/L~1.70 g/L. Besides, low deposition rates were observed with injection velocities around 0.69 cm/min.