Search

To more accurately predict the migration behavior of pollutants in porous media, we conduct laboratory scale experiments and model simulation. Aniline (An) is used in one-dimensional soil column experiments designed under various media and hydrodynamic conditions. The advection-dispersion equation (ADE) and the continuous-time random walk (CTRW) were used to simulate the breakthrough curves (BTCs) of the solute transport. The results show that the media and hydrodynamic conditions are two important factors affecting solute transport and are related to the degree of non-Fickian transport. The simulation results show that CTRW can more effectively describe the non-Fickian phenomenon in the solute transport process than ADE. The sensitive parameter in the CTRW simulation process is β, which can reflect the degree of non-Fickian diffusion in the solute transport. Understanding the relationship of β with velocity and media particle size is conducive to improving the reactive solute transport model. The results of this study provide a theoretical basis for better prediction of pollutant transport in groundwater. This article is protected by copyright. All rights reserved.

Permeability and porosity are the two most important parameters of rocks for the evaluation and exploitation of oil/gas reservoirs. In this study, a modified pulse‐decay method has been developed to measure both permeability and porosity simultaneously. In the present method, the gas pressure in one chamber is changed (increased or decreased) instantaneously and then maintained constant, while the pressure response changing with time in the other one is monitored. A mathematical model of this procedure has been formulated, and a general analytical solution, including the early‐time and late‐time evolutions, has been obtained. The late‐time solution is presented for postprocessing of experimental data, which leads to the simultaneous measurement of permeability and porosity values of tight rocks. Our measurements agree well with those from the classical pulse‐decay and gas expansion methods. Compared with measuring the permeability and porosity separately, the proposed method can reduce the total test time and ensure the permeability and porosity are measured under the same effective stress condition.

We study the process of two-phase flow in thin porous media domains of Brinkman-type. This is generally described by a model of coupled, mixed-type differential equations of fluids' saturation and pressure. To reduce the model complexity, different approaches that utilize the thin geometry of the domain have been suggested. We focus on a reduced model that is formulated as a single nonlocal evolution equation of saturation. It is derived by applying standard asymptotic analysis to the dimensionless coupled model, however, a rigid mathematical derivation is still lacking. In this paper, we prove that the reduced model is the analytical limit of the coupled two-phase flow model as the geometrical parameter of domain's width--length ratio tends to zero. Precisely, we prove the convergence of weak solutions for the coupled model to a weak solution for the reduced model as the geometrical parameter approaches zero.

Porous materials for C2 H2 /CO2 separation mostly suffer from high regeneration energy, poor stability, or high cost that largely dampen their industrial implementation. A desired adsorbent should have an optimal balance between excellent separation performance, high stability, and low cost. We herein report a stable, low-cost, and easily scaled-up aluminum MOF (CAU-10-H) for highly efficient C2 H2 /CO2 separation. The suitable pore confinement in CAU-10-H can not only provide multipoint binding interactions with C2 H2 but also enable the dense packing of C2 H2 inside the pores. This material exhibits one of the highest C2 H2 storage densities of 392 g L-1 and highly selective adsorption of C2 H2 over CO2 at ambient conditions, achieved by a low C2 H2 adsorption enthalpy (27 kJ mol-1 ). Breakthrough experiments confirm its exceptional separation performance for C2 H2 /CO2 mixtures, affording both large C2 H2 uptake of 3.3 mmol g-1 and high separation factor of 3.4. CAU-10-H achieves the benchmark balance between separation performance, stability, and cost for C2 H2 /CO2 separation.

International audience; For the first time, the possibility of obtaining porous germanium from both single-crystal and polycrystalline starting materials using environmentally friendly (in contrast to the commonly used HF and HCl) imidazolium ionic liquids (IL) was shown. It was demonstrated that pore formation depended significantly on the viscosity of the IL, on the etching current density and etching time, and on defects and imperfections of the substrate surface. By varying these parameters, the rates of two competing processes - formation and growth of pores and electropolishing - could be adjusted, consequently allowing germanium with a various structured surface, including a porous surface. In particular, using a more viscous IL (for example, [BMIM][PF6] versus [BMIM][BF4]) made it possible to reduce the rate of dissolution of the germanium dioxide surface layer; as a result, the formation and growth of pores became a dominant process. At the same time, the dissolution rate of the already formed porous layer (electropolishing) increased with the etching current density and the number of defects and imperfections of the germanium surface.

Na3 V2 (PO4 )3 (NVP) has been regarded as a potential cathode material for sodium-ion batteries (SIBs) due to its excellent structural stability and rapid Na+ conductivity. However, its electrochemical performances are restricted by the large bulk structure and poor electronic conductivity. The construction of porous NVP materials is a powerful method to improve the electrochemical properties. This concept aims to provide an overview of recent progress of porous NVP materials for SIBs. Herein, the synthetic strategies and formation mechanisms of porous NVP materials as well as the relationship between the porous structures and electrochemical performances of NVP materials are reviewed. Furthermore, the challenges and prospects for the preparation of porous NVP materials in this field are outlined.

Adsorptive chemical separation is at the forefront of future technologies, for use in chemical and petrochemical industries. In this process, a porous adsorbent selectively allows a single component from a mixture of three or more chemical components to be adsorbed or permeate. To separate the unsorted chemicals, a different adsorbent is needed. A unique adsorbent which can recognize and separate each of the chemicals from a mixture of three or more components is the necessity for the next generation porous materials. In this regard, we demonstrate a "dynamic chemical clip" in a supramolecular framework capable of thermodynamic and kinetics-based chemical separation. The dynamic space, featuring a strong preference for aromatic guests through π-π and C-H⋅⋅⋅π interactions and adaptability, can recognize the individual chemical isomers from mixtures and separate those based on thermodynamic and kinetic factors. The liquid-phase selectivity and separation of the aromatic isomers are possible by the adaptability of the "chemical clip" and here we elucidate the prime factors in a combinatorial approach involving crystallographic evidence and detailed computational studies.

Conventional sonic logging tools are destined mainly for the determination of elastic waves’ velocities. In this paper, we have considered a different type of sonic logging tool that is destined for the registration of parameters of reflected waves in a borehole. We have calculated the mechanical impedance loading an acoustic source located on the axis of a fluid‐filled borehole. The problem was solved for a borehole drilled in a poroelastic formation. The solution was obtained in the framework of the Biot theory of poroelasticity. We have considered two limiting cases with permeable and impermeable (mudcake at the boundary between the borehole and porous rock) borehole wall. We have obtained the frequency dependences of the mechanical impedance. It was shown that the acoustic system ‘logging tool – fluid‐filled borehole – porous rock’ presents several resonance frequencies. These resonances’ frequencies are close to the resonance frequencies of a liquid layer between two rigid cylinders with radii equal to the source and borehole radii. The mechanical impedance calculated at the resonance frequency depends on the porosity and permeability that allows one to use impedance measurements in the frequency range near the resonance to determine the filtration properties of highly permeable rocks (of order higher than 10 mD). We have calculated the mechanical impedance in the low‐frequency range. The results obtained have shown that the use of low‐frequency impedance measurements provides a good way to evaluate the permeability of porous media.

We present a new analytic BRDF for porous materials comprised of spherical Lambertian scatterers. The BRDF has a single parameter: the albedo of the Lambertian particles. The resulting appearance exhibits strong back scattering and saturation effects that height-field-based models such as Oren-Nayar cannot reproduce.

In this study, the time-dependent electrophoretic motion of a conducting spherical particle embedded in an arbitrary electrolyte solution saturated porous medium is investigated. The porous medium is uniformly charged and the embedded hard particle is charged with constant ζ -potential or constant surface charge density. The unsteady modified Brinkman equation with an electric force term, which governs the fluid velocity field, is used to model the porous medium and is solved by Laplace's transform technique. An analytical expression for the electrophoretic velocity of the spherical particle is obtained in Laplace transform domain as a function of the relevant parameters, and its inversion is obtained through numerical techniques. Also, in this study, the steady-state electrophoretic velocity is obtained analytically as linear functions of ζ -potential (or surface density charge) and the fixed charge density. The steady-state electrophoretic velocity is displayed graphically for various relevant parameters and compered with the available data in the literature. Also, the numerical values of the transient electrophoretic velocity are plotted versus the nondimensional elapsed time and discussed for different values of the Debye length parameter, density ratio, permeability of the porous medium, and for high and nonconducting particles.