Dynamics of progressive pore clogging by colloidal aggregates

Separation and Purification Technology, 2012

Prediction of pore fouling by microparticles is still challenging and remains a difficult step to optimize membrane and filtration processes. The scientific issue consists in determining the relevant operation parameters controlling the capture of particles and the clogging of the filter. In this study, we have developed for a dead-end and cross-flow filtration a poly-dimethylsiloxane (PDMS) device which allows direct observation of the clogging dynamics of microchannels (20 lm wide) by micrometric particles (5 lm diameter). The experiments highlight the formation of different 3D clogging patterns according to the filtration conditions (particle concentration, flowrate, particle flux density and physical-chemical conditions of suspension). Besides, we have determined under which specific conditions of filtration, the latex microparticles are captured and form arches, clusters or dendrites. For each type of structure, the temporal dynamics of the particle deposition are analyzed by means of the average thickness of deposit. The critical conditions for the formation of arches leading to deposit formation have been identified in term of a combination of operating conditions: the particle concentration and the particle velocity. A critical particle flux density yielding pore clogging is then observed and characterized. Studying these experimental results helps to identify pore clogging mechanisms: deposition, interception and bridging.

2010

Colloid transport and retention in saturated porous media i s a complex phenomenon that is governed by pore-scale flow field, Brownian fluctuations, and a number of colloid-sur face and colloid-colloid physicochemical interaction forces. Here we develop a computational approach to study th e transport and retention of colloids under unfavorable attachment conditions where interactive surfaces are like charged and a repulsive energy barrier exists. A twodimensional flow model is used to represent a small region of a porous medium containing multiple grains. A direct Lagrangian particle-tracking is used to simulate colloid t ransport by solving the equation of motion for each colloid using a Runge-Kutta method with variable time steps. Suffici ently small time steps are used in zones where fluid velocity and DLVO forces change rapidly. Simulation result show that as long as the primary energy barrier is high enough, colloids cannot overcome the primary energy barrie r and deposition a...

Colloids and Surfaces A: Physicochemical and Engineering Aspects, 1998

The deposition of colloidal particles onto surfaces can be considered a special case of hetero-coagulation. Deposition and detachment kinetics are determined by a combination of colloidal and hydrodynamic factors. For well-defined geometries and for systems in which particle-wall interactions are attractive, the deposition rate can be predicted accurately from first principles. When repulsive interactions are operative, theoretical difficulties arise from a number of sources, such as a coupling between hydrodynamics and electrokinetics, surface charge regulation, and shearinduced modification of configurations of adsorbed polymers. These complications prevent accurate prediction of slow deposition rates. Also, no good a priori models exist to predict detachment rates, although trends can be predicted. Experimental examples will be provided of colloidal particle deposition on flat surfaces in an impinging jet, in which the flow is well defined, and in porous beds consisting of pulp fibers, in which the flow is rather ill defined. Effects of electrolyte and polymers on deposition are discussed.

Physical Review Letters, 2018

From observations of the progressive deposition of noncolloidal particles by geometrical exclusion effects inside a 3D model porous medium, we get a complete dynamic view of particle deposits over a full range of regimes from transport over a long distance to clogging and caking. We show that clogging essentially occurs in the form of an accumulation of elements in pore size clusters, which ultimately

Vadose Zone Journal, 2004

, colloid transport experiments with porous media have been based on mass balance In unsaturated porous media, sorption of colloids at the air-water of breakthrough colloid concentrations in packed-sand (AW) interface is accepted as a mechanism for controlling colloid retention and mobilization. However, limited actual pore-scale obser-columns (Wan and vations of colloid attachment to the AW interface have been made. To Jewett et al., 1999; Jin et al., 2000; Lenhart and Saiers, further investigate these processes, a real-time pore-scale visualization 2002). On the basis of analyses of outflow concentrations method was developed. The method builds on the light transmission of colloid particles, these authors found that more partitechnique for fingered flow studies in packed-sand infiltration chamcles were retained in the column at lower water contents bers and combines it with high-resolution, electro-optical hardware (or under conditions where there were higher percentand public domain imaging software. Infiltration and drainage of ages of trapped air). Retention, measured as reduced suspensions of hydrophilic negatively charged carboxylated latex micolloid concentrations in the column outflow, was attribcrospheres provides compelling visual evidence that colloid retention uted to sorption at the AW interface and film straining. in sandy porous media occurs via trapping in the thin film of water In one case retention of bacteriophages in a batch syswhere the AW interface and the solid interface meet, the air-watersolid (AWS) interface. With this modified theory of trapped colloids sity,

Water Resources Research, 2006

1] Colloid transport was studied at the pore scale in order to gain insight into the microscale processes governing particle removal. Monodisperse suspensions of colloids and water-saturated micromodels were employed. Experiments were carried out for different particle sizes, grain surface roughness, solution ionic strength, and flow rates. Straining and attachment were observed and measured by tracking the trajectory and fate of individual colloids using optical microscopy. Classical filtration theory proved appropriate for throat to colloid ratios (T/C) larger than 2.5 but did not take into account the possibility of straining that becomes an important capture mechanism for smaller T/C ratios. Spatially within the porous medium, straining occurred within the first 1-2 pore throats, while interception and attachment was seen from the inlet to the first 6-10 pore spaces, depending on particle size. Once a particle passed the initial region, the probability of attachment was very small. Colloid attachment increased with increasing solution ionic strength or decreasing flow rate, whereas straining was mainly independent of flow rate. Surface roughness of the grains also played a significant role in colloid capture, increasing collision efficiency by a factor of 2-3. The mechanisms of removal and the spatial distribution of colloid retention differed noticeably as a function of the T/C ratio. Micromodel visualizations clearly showed that physical straining and the effect of surface roughness should be taken into account when predicting the transport of colloids in saturated porous media.

Environmental Science & Technology, 2013

The prediction of colloid transport in unsaturated porous media in the presence of large energy barrier is hampered by scant information of the proportional retention by straining and attractive interactions at surface energy minima. This study aims to fill this gap by performing saturated and unsaturated column experiments in which colloid pulses were added at various ionic strengths (ISs) from 0.1 to 50 mM. Subsequent flushing with deionized water released colloids held at the secondary minimum. Next, destruction of the column freed colloids held by straining. Colloids not recovered at the end of the experiment were quantified as retained at the primary minimum. Results showed that net colloid retention increased with IS and was independent of saturation degree under identical IS and Darcian velocity. Attachment rates were greater in unsaturated columns, despite an over 3-fold increase in pore water velocity relative to saturated columns, because additional retention at the readily available air-associated interfaces (e.g., the air−water− solid [AWS] interfaces) is highly efficient. Complementary visual data showed heavy retention at the AWS interfaces. Retention by secondary minima ranged between 8% and 46% as IS increased, and was greater for saturated conditions. Straining accounted for an average of 57% of the retained colloids with insignificant differences among the treatments. Finally, retention by primary minima ranged between 14% and 35% with increasing IS, and was greater for unsaturated conditions due to capillary pinning. ■ INTRODUCTION Colloidal transport in porous media has gained notable attention over the past few decades as facilitated contaminant transport in groundwater aquifers, reduced permeability of oil and gas reservoirs, and in situ remediation strategies have become topics of concern in various fields. 1,2 A large body of experimental and theoretical work has been carried out to understand key physicochemical factors affecting colloid transport and deposition in natural porous media. Solution composition has been extensively investigated with particular emphasis on ionic strength (IS) 3−5 and pH 5−8 for affecting electrostatic interactions, natural organic matter, 5,8 and surfactants as electrosteric stabilizers, and cation valence 8 in terms of neutralizing surface charge. Each of these factors affects surface interactions between colloids and between colloids and the porous medium's surface. In addition, unsaturated conditions significantly increase colloid retention by the presence of a gas phase, which restricts the geometry of the fluid phase and partitions deposited colloids toward interfaces that are absent in fully saturated media (e.g., air− water and air−water−solid interfaces). 9−15 Flow rate affects low-flow or flow-stagnation zones where colloids can become trapped. 3,15 Moreover, high flow velocities have been related to increased applied torque from strong hydrodynamic drag forces

This review paper will serve to explain how a particle is trapped on a porous media, and describe the mobility of those particles when passing through a media. It also presents the different parameters that play an important role on the trapping mechanism and the role of biofilm formation. The deposition and trapping mechanism of particles in porous media is governed by the action of different mechanisms such as interception, sieving, diffusion, gravitational and Van Der Waals forces, Brownian diffusion, and inertia. The particle retention through the porous media leads to the formation of a biofilm and the clogging of the media. The understanding of particle retention, clogging, and biofilm formation is interesting because it plays a major role in soil recovery process such as bioremediation, biosorption and filtration (on sand and activated carbon) used for degradation of particles (colloids and microorganisms) and harmful contaminants (heavy metals, drugs) by microorganisms.

Vadose Zone …, 2005

, colloid transport experiments with porous media have been based on mass balance In unsaturated porous media, sorption of colloids at the air-water of breakthrough colloid concentrations in packed-sand (AW) interface is accepted as a mechanism for controlling colloid retention and mobilization. However, limited actual pore-scale obser-columns (Wan and vations of colloid attachment to the AW interface have been made. To Jewett et al., 1999; Jin et al., 2000; Lenhart and Saiers, further investigate these processes, a real-time pore-scale visualization 2002). On the basis of analyses of outflow concentrations method was developed. The method builds on the light transmission of colloid particles, these authors found that more partitechnique for fingered flow studies in packed-sand infiltration chamcles were retained in the column at lower water contents bers and combines it with high-resolution, electro-optical hardware (or under conditions where there were higher percentand public domain imaging software. Infiltration and drainage of ages of trapped air). Retention, measured as reduced suspensions of hydrophilic negatively charged carboxylated latex micolloid concentrations in the column outflow, was attribcrospheres provides compelling visual evidence that colloid retention uted to sorption at the AW interface and film straining. in sandy porous media occurs via trapping in the thin film of water In one case retention of bacteriophages in a batch syswhere the AW interface and the solid interface meet, the air-watersolid (AWS) interface. With this modified theory of trapped colloids sity,

Langmuir, 2010

The hemispheres-in-cell model for colloid transport and deposition in simple granular filtration media preserves the utilities provided in the Happel sphere-in-cell but also incorporates features (e.g., grain-to-grain contact) that are shown to drive colloid deposition from experiments and simulations when colloid-surface repulsion exists (Ma, H.;