Colloid Adhesive Parameters for Chemically Heterogeneous Porous Media
TL;DR: The model results show that the PDFs of colloid adhesive parameters at the REA scale were sensitive to the size of the colloid and the heterogeneity, the charge and number of grid cells, and the ionic strength.
Abstract: A simple modeling approach was developed to calculate colloid adhesive parameters for chemically heteroge- neous porous media. The area of the zone of electrostatic influence between a colloid and solid−water interface (Az) was discretized into a number of equally sized grid cells to capture chemical heterogeneity within this region. These cells were divided into fractions having specific zeta potentials (e.g., negative or positive values). Mean colloid adhesive parameters such as the zeta potential, the minimum and maximum in the interaction energy, the colloid sticking efficiency (α), and the fraction of the solid surface area that contributes to colloid immobilization (Sf) were calculated for possible charge realizations within Az. The probability of a given charge realization in Az was calculated using a binomial mass distribution. Probability density functions (PDFs) for the colloid adhesive parameters on the heterogeneous surface were subsequently calculated at the representative elementary area (REA) scale for a porous medium. This approach was applied separately to the solid−water interface (SWI) and the colloid, or jointly to both the SWI and colloid. To validate the developed model, the mean and standard deviation of the interaction energy distribution on a chemically heterogeneous SWI were calculated and demonstrated to be consistent with published Monte Carlo simulation output using the computationally intensive grid surface integration technique. Our model results show that the PDFs of colloid adhesive parameters at the REA scale were sensitive to the size of the colloid and the heterogeneity, the charge and number of grid cells, and the ionic strength.
Citations
More filters
TL;DR: The analytical methods, occurrence, transport, and potential ecological risks of microplastics in soil environments have been reviewed and a universal, efficient, faster, and low-cost analytical method is still not available.
209 citations
TL;DR: The antagonistic effects of HA and iron oxyhydroxide grain-coating imparted on the mobility of biochar NPs suggest that biochar colloid transport potential will be dependent on competitive influences exerted by a number of environmental factors.
Abstract: Biochar land application may result in multiple agronomic and environmental benefits (e.g., carbon sequestration, improving soil quality, and immobilizing environmental contaminants). However, our understanding of biochar particle transport is largely unknown in natural environments with significant heterogeneity in solid (e.g., patches of iron oxyhydroxide coating) and solution chemistry (e.g., the presence of natural organic matter), which represents a critical knowledge gap in assessing the environmental impact of biochar land application. Transport and retention kinetics of nanoparticles (NPs) from wheat straw biochars produced at two pyrolysis temperatures (i.e., 350 and 550 °C) were investigated in water-saturated sand columns at environmentally relevant concentrations of dissolved humic acid (HA, 0, 1, 5, and 10 mg L(-1)) and fractional surface coverage of iron oxyhydroxide coatings on sand grains (ω, 0.16, 0.28, and 0.40). Transport of biochar NPs increased with increasing HA concentration, largely because of enhanced repulsive interaction energy between biochar NPs and sand grains. Conversely, transport of biochar NPs decreased significantly with increasing ω due to enhanced electrostatic attraction between negatively charged biochar NPs and positively charged iron oxyhydroxides. At a given ω of 0.28, biochar NPs were less retained with increasing HA concentration due to increased electrosteric repulsion between biochar NPs and sand grains. Experimental breakthrough curves and retention profiles were well described using a two-site kinetic retention model that accounted for Langmuirian blocking or random sequential adsorption at one site. Consistent with the blocking effect, the often observed flat retention profiles stemmed from decreased retention rate and/or maximum retention capacity at a higher HA concentration or smaller ω. The antagonistic effects of HA and iron oxyhydroxide grain-coating imparted on the mobility of biochar NPs suggest that biochar colloid transport potential will be dependent on competitive influences exerted by a number of environmental factors (e.g., natural organic matter and metal oxides).
164 citations
TL;DR: A detailed review of the experimental works brings out the essential mechanisms and particle resuspension is shown to result from a balance between particle-fluid interactions and particle-surface interactions influenced by surface heterogeneities (roughness).
149 citations
TL;DR: A balance of applied hydrodynamic and resisting adhesive torques was conducted over a chemically heterogeneous porous medium to determine the fraction of the solid surface area that contributes to colloid immobilization (S(f)*) under unfavorable attachment conditions.
Abstract: A balance of applied hydrodynamic (TH) and resisting adhesive (TA) torques was conducted over a chemically heterogeneous porous medium that contained random roughness of height hr to determine the fraction of the solid surface area that contributes to colloid immobilization (Sf*) under unfavorable attachment conditions. This model considers resistance due to deformation and the horizontal component of the adhesive force (FAT), spatial variations in the pore scale velocity distribution, and the influence of hr on lever arms for TH and TA. Values of Sf* were calculated for a wide range of physicochemical properties to gain insight into mechanisms and factors influencing colloid immobilization. Colloid attachment processes were demonstrated to depend on solution ionic strength (IS), the colloid radius (rc), the Young’s modulus (K), the amount of chemical heterogeneity (P+), and the Darcy velocity (q). Colloid immobilization was also demonstrated to occur on a rough surface in the absence of attachment. In th...
140 citations
TL;DR: Results demonstrated that the density and height of NSR significantly influenced the interaction energy parameters and consequently the extent and kinetics of colloid retention and release, and yielded a much weaker primary minimum interaction compared with that of smooth surfaces.
137 citations
Cites background from "Colloid Adhesive Parameters for Che..."
...Numerous studies have pointed out the inadequacy of classicaland extended-DLVO calculations in explaining colloid retention and release in porous media (Bradford and Torkzaban, 2012; Tong et al., 2008; Tufenkji and Elimelech, 2005)....
[...]
References
More filters
Book•
01 Jan 1985
TL;DR: The forces between atoms and molecules are discussed in detail in this article, including the van der Waals forces between surfaces, and the forces between particles and surfaces, as well as their interactions with other forces.
Abstract: The Forces between Atoms and Molecules. Principles and Concepts. Historical Perspective. Some Thermodynamic Aspects of Intermolecular Forces. Strong Intermolecular Forces: Covalent and Coulomb Interactions. Interactions Involving Polar Molecules. Interactions Involving the Polarization of Molecules. van der Waals Forces. Repulsive Forces, Total Intermolecular Pair Potentials, and Liquid Structure. Special Interactions. Hydrogen-Bonding, Hydrophobic, and Hydrophilic Interactions. The Forces between Particles and Surfaces. Some Unifying Concepts in Intermolecular and Interparticle Forces. Contrasts between Intermolecular, Interparticle, and Intersurface Forces. van der Waals Forces between Surfaces. Electrostatic Forces between Surfaces in Liquids. Solvation, Structural and Hydration Forces. Steric and Fluctuation Forces. Adhesion. Fluid-Like Structures and Self-Assembling Systems. Micelles, Bilayers, and Biological Membranes. Thermodynamic Principles of Self-Assembly. Aggregation of Amphiphilic Molecules into Micelles, Bilayers, Vesicles, and Biological Membranes. The Interactions between Lipid Bilayers and Biological Membranes. References. Index.
18,048 citations
TL;DR: In this paper, the influence of surface energy on the contact between elastic solids is discussed and an analytical model for its effect upon the contact size and the force of adhesion between two lightly loaded spherical solid surfaces is presented.
Abstract: This paper discusses the influence of surface energy on the contact between elastic solids. Equations are derived for its effect upon the contact size and the force of adhesion between two lightly loaded spherical solid surfaces. The theory is supported by experiments carried out on the contact of rubber and gelatine spheres.
6,981 citations
TL;DR: Theory of the Stability of Lyophobic Colloids The Interaction of Sol Particles having an Electric Double Layer and the nature of the electrical double layer which exists around them in salt solutions is discovered.
Abstract: MANY of the classical investigations of colloidal chemistry were concerned with the stability of colloidal solutions of insoluble substances, such as gold, arsenic sulphide, silver halides, etc. The well-known phenomenon of coagulation of these sols by comparatively small concentrations of electrolytes suggested that their stability was connected with their electric charges. A considerable amount of research has been made in the past to discover the magnitude and origin of the electric charge on the particles and the nature of the electrical double layer which exists around them in salt solutions. Although qualitative and semi-quantitative explanations have been given of the phenomenon of coagulation and of the rule of Hardy and Schulze, according to which the ionic concentration required for precipitation diminishes rapidly with the charge of the effective ion, yet a complete and satisfactory theory was still lacking. Theory of the Stability of Lyophobic Colloids The Interaction of Sol Particles having an Electric Double Layer. By E. J. W. Verwey and J. Th. G. Overbeek., with the collaboration of K. van Nes. Pp. xi + 205. (New York and Amsterdam : Elsevier Publishing Co., Inc. ; London : Cleaver-Hume Press, Ltd., 1948.) 22s. 6d. net.
3,099 citations