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Pore-network models are powerful tools for studying particle transport in complex porous media, and investigating the role of interfaces in their fate. The first step in simulating particle transport using pore-network models is to quantitatively describe particle transport in a single pore, and obtain relationships between pore-averaged deposition rate coefficients and various pore-scale parameters. So, in this study, a three-dimensional (3D) mathematical model is developed to simulate the transport and retention of nanoparticles within a single partially saturated pore with an angular cross-section. The model accounts for particle deposition at solid-water interfaces (SWIs), air-water interfaces (AWIs), and air-water-solid (AWS) contact regions. We provide a novel formulation for particle diffusive transport from AWI to AWS, where particles are assumed to be retained irreversibly by capillary forces. The model involves 12 dimensionless parameters representing various physicochemical conditions. The 3D model results are averaged over the pore cross-section and then fitted to breakthrough curves from one-dimensional (1D) advection-dispersion-sorption equations with three-site kinetics to estimate 1D-averaged deposition rate coefficients at interfaces. We find that half-corner angle, particle size, radius of curvature of AWI, and mean flow velocity have a significant effect on those coefficients. In contrast, chemical parameters such as ionic strength and surface potentials of particles and interfaces have negligible effects. AWS is found to be the major retention site for particles, especially for hydrophobic particles. We develop algebraic relationships between 1D-averaged deposition rate coefficients at interfaces vis-à-vis various pore-scale parameters. These relationships are needed for pore-network models to upscale nanoparticle transport to continuum scale.

Two different grades, WC-20 vol.% Ni and WC-20 vol.% Co cemented carbides, respectively were systematically investigated concerning their microstructure, binder composition, and corrosion behavior. SEM-EBSD analysis verified that both grades have similar WC grain sizes (0.9-1.1 mu m). AES analysis confirmed that the binder phase of the respective grade is an alloy of Ni-W and Co-W and that the concentration of W in the Ni-and Co-binder is 21 and 10 at. %, respectively. In synthetic mine water (SMW), the EIS behavior of WC-Ni(W) at the open circuit potential (OCP) conditions was studied for different exposure periods (up to 120 h). The EIS data fitting estimates low capacitance and high charge transfer resistance (Rct) values, which indicate that the passive film formed on WC-Ni(W) is thin and exhibits high corrosion resistance. At the OCP and potentiostatic-passive conditions, SEM investigations confirm the uncorroded microstructure of the WC-Ni(W). The AR-XPS studies confirmed the formation of an extremely thin (0.25 nm) WO3 passive film is responsible for the high corrosion resistance of WC-Ni(W), at OCP conditions. However, above the transpassive potential, the microstructure instability of WC-Ni(W) was observed, i.e., corroded morphology of both WC grains and Ni(W) binder. The electrochemical parameters, Rct, corrosion current density, and charge density values, confirmed that the WC-Ni(W) is a far better alternative than the WC-Co(W) for application in SMW.