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DLVO energy profiles for the 1156 nm colloid interacting with the planar surface carrying a hemisphere with different radii (a, 100 nm; b, 5 nm; c, 20 nm; d, 15 nm) at different ionic strengths (black, 0.2 M; pink, 0.01 M; red, 0.001 M; blue, 0.0001 M). The calculated primary minimum depth (Upri), maximum energy barrier (Umax), and secondary minimum depth (Usec) are also shown.
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The Derjaguin-Landau-Verwey-Overbeek (DLVO) interaction energy profile has been frequently used to interpret the mechanisms controlling colloid attachment/detachment and aggregation/disaggregation behavior. This study highlighted a type of energy profile that is characterized by a shallow primary energy well (i.e., comparable to the average kinetic...
Citations
... SPMzero association at pH 5 (positive charge of hematite) yielded a larger plateau floc size at 60 min (mode dV = 15.42 ± 0.96 µm, within-batch), than flocs associated at 0.1 mM electrolytes (mode dV = 7.3 ± 0.4 µm), in accordance with hematite being more positively charged in absence of electrolytes (Figure S3-2).The modification of hydrochemistry to 0.1 mM electrolytes & 1 ppmC SR-NOM in course of a 1:1 dilution of both, freshly associated and overnight shaker-equilibrated SPMzero, did not induce disintegration of flocs (Figures S8-3 and S8-4), even though these hydrochemical conditions prohibited flocculation(Figure 7 a). Agglomeration is frequently reported to not be fully reversible and de-agglomeration by unfavorable hydrochemistry produces fragments rather than single particles Loosli et al., 2013; Mohd Omar et al., 2014), as probably mainly weak bonds (secondary minima) are broken(Philippe and Schaumann, 2014;Wang et al., 2016). Still, the extent of de-agglomeration was found to increase with concentration of stabilizing NOM and with reaction time, as molecules slowly migrate into agglomerates Loosli et al., 2013). ...
Aquatic fate models and risk assessment require experimental information on the potential of contaminants to interact with riverine suspended particulate matter (SPM). While for dissolved contaminants partition or sorption coefficients are used, the underlying assumption of chemical equilibrium is invalid for particulate contaminants, such as engineered nanomaterials, incidental nanoparticles, micro- or nanoplastics. Their interactions with SPM are governed by physicochemical forces between contaminant-particle and SPM surfaces. The availability of a standard SPM material is thus highly relevant for the development of reproducible test systems to evaluate the fate of particulate contaminants in aquatic systems. Finding suitable SPM analogues, however, is challenging considering the complex composition of natural SPM, which features floc-like structures comprising minerals and organic components from the molecular to the microorganism level. Complex composition comes with a heterogeneity in physicochemical surface properties, that cannot be neglected. We developed a procedure to generate SPM analogue flocs from components selected to represent the most abundant and crucial constituents of natural riverine SPM, and the process-relevant SPM surface characteristics regarding interactions with particulate contaminants. Four components, i.e., illite, hematite, quartz and tryptophan, combined at environmentally realistic mass-ratios, were associated to complex flocs. Flocculation was reproducible regarding floc size and fractal dimension, and multiple tests on floc resilience towards physical impacts (agitation, sedimentation-storage-resuspension, dilution) and hydrochemical changes (pH, electrolytes, dissolved organic matter concentration) confirmed their robustness. These reproducible, ready-to-use SPM analogue flocs will strongly support future research on emerging particulate contaminants.
... Another explanation could be spontaneous fines detachment by Brownian motion or some external mechanical vibration. 293−295 Yet, the corresponding theory and mathematical model have not been developed. ...
... In the case of stable dispersion (absence of aggregations) of smaller nanoparticles (way lower than pore throat size), surface deposition would be the major mechanism that contributes significantly in nanoparticles retention [6,188]. The mechanism of surface deposition can be appeared due to combination of various interactions or forces such as entropic force, steric forces (in the case of coated nanoparticles), born repulsion, van der Waals (VdW)force and electrostatic interaction [6,19,33,177,188]. In addition, nanoparticles also experience gravitational and hydrodynamic forces during their flow in porous media that are considered to be negligible compared to the Brownian/viscous forces due their much smaller size (1-100 nm) (refer to Section 4). ...
Stability of nanofluids along with their promising properties has led to wide applications of nanoparticles (NPs) in enhanced oil recovery (EOR) projects. Nanofluids that are colloidal suspension of NPs in base fluids, can stay stable at harsh reservoir conditions where other chemical-EOR solutions made of surfactants and polymers start degrading and lose their stabilities and functionalities. Specific surface characteristics of NPs have made them to affect fluids and rock properties and their pair interactions in porous media in favor of EOR mechanisms. Nevertheless, applying NPs in subsurface projects needs a strong understanding of NPs behaviors and their functions in porous media. As such, this work aims to give deeper insight into NPs functionality in porous media needed for practical design of NPs-EOR projects. This review endeavors to analyze the nanoparticle behaviors in porous media in view of criteria needed for application in EOR subsurface projects. Different promising mechanisms for NPs assisted EOR followed by controlling factors to optimize the EOR efficiency are deliberated. Effect of interparticle interactions along with other hydrodynamic forces on dispersion stability, nanoparticle agglomerations and subsequent settling have been analyzed in order to prepare stable nanofluid(s) for their further implications in EOR. Transport of NPs through porous media with the associated challenges is also investigated. Recent studies on NPs assisted EOR techniques are also presented. Finally, EOR challenges using NPs and the needed future research are highlighted.
... The presence of nanoscale physical asperities (NPAs) and charge heterogeneities can locally reduce the interaction energy barrier and increase nC 60 NPs deposition in primary minima (Li et al., , 2017Tong et al., 2010;Shen et al., 2018Shen et al., , 2019aShen et al., , 2019b. However, the nC 60 NPs deposited atop NPAs at primary minima can spontaneously detach even by Brownian diffusion because the NPAs can significantly reduce primary minimum depth and the adhesion acting on the NPs (Wang et al., 2016b). The secondary minima were shallow for the nC 60 NPs, which may not cause the immobilization at the energy wells . ...
... PVs of NP-free electrolyte solution (Phase 2), and finally DI water (Phase 3). This three-step procedure has been widely employed in previous studies (Shen et al., 2012;Wang et al., 2016b;Li et al., 2017) ...
... The nC 60 NPs were assumed J o u r n a l P r e -p r o o f Journal Pre-proof to be spherical and the sand surface was taken as plate. The use of SEI technique to calculate energies for sphere-plate interaction can be referred to previous studies (Wang et al., 2016a(Wang et al., , 2016bLi et al., 2017;Shen et al., 2018). Briefly, surfaces of both a NP and sand were discretized into small area elements. ...
Sand column experiments were performed under saturated conditions to investigate impact of humic acid (HA) on attachment of nC60 nanoparticles (NPs) in NaCl and CaCl2 at ionic strengths (ISs) from 1 mM to 100 mM and subsequent detachment via reducing solution IS. The attachment increased with increasing IS due to reduced repulsive Derjaguin-Landau-Verwey-Overbeek (DLVO) interaction energy and accordingly increased retention in primary energy wells. More attachments occurred in CaCl2 compared to NaCl because Ca2+ exhibited greater charge screen ability and served as a bridging agent between the NPs and sand surfaces. The presence of HA significantly reduced nC60 NPs attachment on sand surfaces (especially on nanoscale physical heterogeneities) in 10 mM NaCl and 1 mM CaCl2 because of enhanced electrostatic and steric repulsions. Interestingly, although the HA did not cause reduction of attachment in 100 mM NaCl and 10 mM CaCl2 compared to the case in absence of HA, the HA caused weak attachment of nC60 on sand surfaces and then much more significant detachment by decreasing IS. The HA did not alter both attachment and detachment in 100 mM CaCl2, because the Ca2+ at the high concentration caused formation of very stable complex of HA and NPs, and strong interaction of the complex with the sand surfaces via cation bridge. Our study highlighted that the HA can not only enhance the transport of NPs by inhibiting attachment as revealed in the literature, but also by the continuous capture and release of the NPs from surfaces in subsurface environments.
... Whether the surface roughness increases or decreases primary-minimum attachment is dependent on the overall effects of these roughness parameters (Abdelfatah, Kang, Pournik, Shiau, & Harwell, 2017;. However, existing theoretical studies (Chen, Bedi, Yan, & Walker, 2010;Jin, Glawdel, et al., 2015;Jin, Normani, et al., 2015;Jin, Ren, & Emelko, 2016;Shellenberger & Logan, 2002;Shen et al., 2011;2015;Wang, Jin, et al., 2016) ; frequently used only a single parameter (e.g. average height) to characterize the surface roughness and evaluate its effect on primary-minimum attachment. ...
... sand grain). As mentioned previously, existing studies (Chen et al., 2010;Jin, Glawdel, et al., 2015;Jin, Normani, et al., 2015;Jin et al., 2016;Shellenberger & Logan, 2002;Shen et al., 2011;2015;Wang, Jin et al., 2016) ; frequently used a single parameter (e.g. average roughness height) to represent heterogeneity and determined the relationship between the average value of a and the heterogeneity parameter. ...
... Only minor amount of particles can spontaneously detach from primary or secondary minima by Brownian diffusion ( Wang, Jin et al., 2016) . For significant detachment of particles, a physical or chemical disturbance to the system condition is necessary ( Bergendahl & Grasso, 1999, Bergendahl & Grasso, 2000. ...
Knowledge of particle deposition and transport in saturated porous media is of significant importance for various engineered applications and environmental concerns. Surface physical and chemical heterogeneities play a critical role in particle deposition because they can increase attachment in the primary minima of Derjaguin-Landau-Verwey-Overbeek (DLVO) interaction energy profile by reducing the repulsive energy barrier. We present a comprehensive review showing that surface heterogeneity can alter particle deposition through multiple additional mechanisms such as increasing attachment at secondary minima at concave locations and detachment from primary minima at nanoscale convex asperities. The pore-scale deposition mechanisms due to surface heterogeneity can cause anomalous particle retention and transport behaviors at continuum scales such as equilibrium sorption and nonmonotonic retention profiles. To accurately determine the particle transport in porous media at continuum scales requires future research: (1) improving existing techniques to accurately measure and represent surface heterogeneities and determine attachment and detachment; (2) using statistic models to characterize variations of attachment and detachment with surface heterogeneity; (3) using Lagrangian/Eulerian approach to thoroughly understand pore-scale retention mechanisms in porous media, and incorporating them into continuum equations to simulate particle transport at continuum scales.
... The potential energy barrier at close approach may be considered too high for a bacterium to overcome and adhere in the primary minimum as a whole in all cases. 27 Due to the relatively strong electron-donating and electron-accepting parameters of glass as compared with DDS-coated glass, both strains will also experience large monopolar repulsion at close approach, that will be far less or absent on hydrophobic, DDScoated glass than on hydrophilic glass (see also Table 2). For S. salivarius HBC12 on glass monopolar repulsion ΔG AB (d 0 ) amounts +30.4 mJ m −2 , turning into attraction (−10.6 mJ m −2 ) on DDS-coated glass, but since this is at the distance of closest approach d 0 , it is not reflected in the interaction energies presented in Figure 2 according to the DLVO theory as applied. ...
Models for bacterial adhesion to substratum surfaces all include uncertainty with respect to the (ir)reversibility of adhesion. In a model, based on vibrations exhibited by adhering bacteria parallel to a surface, adhesion was described as a result of reversible binding of multiple bacterial tethers that detach from and successively re-attach to a surface, eventually making bacterial adhesion irreversible. Here, we use Total Internal Reflection Microscopy to determine whether adhering bacteria also exhibit variations over time in their perpendicular distance above surfaces. Streptococci with fibrillar surface tethers showed perpendicular vibrations with amplitudes of around 5 nm, regardless of surface hydrophobicity. Adhering, non-fibrillated streptococci vibrated with amplitudes around 20 nm above a hydrophobic surface. Amplitudes did not depend on ionic strength for either strain. Calculations of bacterial energies from their distances above the surfaces using the Boltzman equation showed that bacteria with fibrillar tethers vibrated as an harmonic oscillator. The energy of bacteria without fibrillar tethers varied with distance in a comparable fashion as the DLVO (Derjaguin, Landau, Verwey and Overbeek)-interaction energy. Distance variations above the surface over time of bacteria with fibrillar tethers are suggested to be governed by the harmonic oscillations, allowed by elasticity of the tethers, piercing through the potential energy barrier. Bacteria without fibrillar tethers “float” above a surface in the secondary energy minimum, with their perpendicular displacement restricted by their thermal energy and the width of the secondary minimum. The distinction between “tether-coupled” and “floating” adhesion is new, and may have implications for bacterial detachment strategies.
... The hydrodynamic force and torque depend on the average pore-water velocity, the grain size distribution, microscopic roughness, porosity, and colloid size (Bradford et al., 2011b;Burdick et al., 2001;Kuznar and Elimelech, 2007;O'Neill, 1968;Saffman, 2006;Torkzaban et al., 2007;Torkzaban et al., 2008). In many instances, the strength of the adhesive interaction is weak, and a fraction of retained colloids are susceptible to diffusive and/or hydrodynamic removal (Torkzaban et al., 2007;Wang et al., 2016). This result has been used to explain the velocity dependency of α and S f (Torkzaban et al., 2007). ...
... Interestingly, the value of ΔФ d was also rather small (b 5.1 kT), especially at intermediate IS (30 and 50 mM) conditions. The Maxwellian kinetic energy model predicts a rapid increase in the probability of cells to diffuse into or out of a primary minimum when Δ Φ a and Δ Φ d are b10 kT Simoni et al., 1998;Torkzaban and Bradford, 2016;Wang et al., 2016). These relatively low values of ΔΦ a (0.1-8.7 kT) and ΔΦ d (5.1-6.0 kT), therefore, indicate that reversible primary minimum interactions are possible under all of the IS conditions. ...
Escherichia coli transport and release experiments were conducted to investigate the pore-water velocity (v) dependency of the sticking efficiency (α), the fraction of the solid surface area that contributed to retention (Sf), the percentage of injected cells that were irreversibly retained (Mirr), and cell release under different (10–300 mM) ionic strength (IS) conditions. Values of α, Sf, and Mirr increased with increasing IS and decreasing v, but the dependency on v was greatest at intermediate IS (30 and 50 mM). Following the retention phase, successive increases in v up to 100 or 150 m day− 1 and flow interruption of 24 h produced negligible amounts of cell release. However, excavation of the sand from the columns in excess electrolyte solution resulted in the release of > 80% of the retained bacteria. These observations were explained by: (i) extended interaction energy calculations on a heterogeneous sand collector; (ii) an increase in adhesive strength with the residence time; and (iii) torque balance consideration on rough surfaces. In particular, α, Sf, and Mirr increased with IS due to lower energy barriers and stronger primary minima. The values of α, Sf, and Mirr also increased with decreasing v because the adhesive strength increased with the residence time (e.g., an increased probability to diffuse over the energy barrier) and lower hydrodynamic forces diminished cell removal. The controlling influence of lever arms at microscopic roughness locations and grain-grain contacts were used to explain negligible cell removal with large increases in v and large amounts of cell recovery following sand excavation. Results reveal the underlying causes (interaction energy, torque balance, and residence time) of the velocity dependency of E. coli retention and release parameters (ksw, α, and Sf) that are not accounted for in colloid filtration theory.
... When the colloid association with the solid surface is not strong enough to be permanently retained, particles can be subject to reversible deposition and thereby detachment. Particles can be maintained temporary when they are trapped at a shallow DLVO secondary minimum [31,33] or as recently found even at a shallow primary minimum resulted from nanoscale surface heterogeneities [169,170], or held at the surface by hydrodynamic forces. Depending on how fast the diffusion of the material is, the process of attachment-detachment can be considered in form of either fast forward-backward interactions of particles or discrete retention-re-entrainment of particles [102,165,167,171]. ...
Environmental applications of NP increasingly result in widespread NP distribution within porous media where they are subject to various concurrent transport mechanisms including irreversible deposition, attachment/detachment (equilibrium or kinetic), agglomeration, physical straining, site-blocking, ripening, and size exclusion. Fundamental research in NP transport is typically conducted at small scale, and theoretical mechanistic modeling of particle transport in porous media faces challenges when considering the simultaneous effects of transport mechanisms. Continuum modeling approaches, in contrast, are scalable across various scales ranging from column experiments to aquifer. They have also been able to successfully describe the simultaneous occurrence of various transport mechanisms of NP in porous media such as blocking/straining or agglomeration/deposition/detachment. However, the diversity of model equations developed by different authors and the lack of effective approaches for their validation present obstacles to the successful robust application of these models for describing or predicting NP transport phenomena.
Aquatic fate models and risk assessment require experimental information on the potential of contaminants to interact with riverine suspended particulate matter (SPM). While for dissolved contaminants partition or sorption coefficients are used, the underlying assumption of chemical equilibrium is invalid for particulate contaminants, such as engineered nanomaterials, incidental nanoparticles, micro- or nanoplastics. Their interactions with SPM are governed by physicochemical forces between contaminant-particle and SPM surfaces. The availability of a standard SPM material is thus highly relevant for the development of reproducible test systems to evaluate the fate of particulate contaminants in aquatic systems. Finding suitable SPM analogues, however, is challenging considering the complex composition of natural SPM, which features floc-like structures comprising minerals and organic components from the molecular to the microorganism level. Complex composition comes with a heterogeneity in physicochemical surface properties, that cannot be neglected. We developed a procedure to generate SPM analogue flocs from components selected to represent the most abundant and crucial constituents of natural riverine SPM, and the process-relevant SPM surface characteristics regarding interactions with particulate contaminants. Four components, i.e., illite, hematite, quartz and tryptophan, combined at environmentally realistic mass-ratios, were associated to complex flocs. Flocculation was reproducible regarding floc size and fractal dimension, and multiple tests on floc resilience towards physical impacts (agitation, sedimentation-storage-resuspension, dilution) and hydrochemical changes (pH, electrolytes, dissolved organic matter concentration) confirmed their robustness. These reproducible, ready-to-use SPM analogue flocs will strongly support future research on emerging particulate contaminants.
