Effect of particle size on collision efficiency in the deposition of Brownian particles with electrostatic energy barriers

Elimelech, Menachem; O’Melia, Charles R.

doi:10.1021/la00096a023

Cited by 362 publications

(336 citation statements)

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“…Additional deposition of the larger particles is inertia impaction (Cohen et al 1990). Electrostatic forces may have an effect on the enhanced deposition of smaller particles (Elimelech and O'Meliat 1990;Semmler et al 1998). In the present experimental calibration, the impact of the particle charge should be minor because the PSL particles used for calibration were electrically neutral particles and electrostatic forces might not be important since the plates making up the DS were metal.…”

Section: Sampling Techniquementioning

confidence: 94%

“…Hence, the charged smaller particles in the atmosphere could enhance the measured PN concentrations by the DS. Secondly, since surface charge density of acidic particles is usually higher than that of non-acidic particles (Elimelech and O'Meliat 1990), and acidic particles in the smaller size have the higher fraction than in the larger size of the total particles, electrostatic forces might cause more acidic particles to be deposited on the DS. Thirdly, subsequent evaporation of volatile species in particles would shift the size distribution to smaller size ranges, increasing the charging percentage of the particles entering the DS.…”

Section: Validation Of the Diffusion Samplermentioning

confidence: 99%

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Diffusion Sampler for Measurement of Acidic Ultrafine Particles in the Atmosphere

Wang

Guo

Chan

2014

Aerosol Science and Technology

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The adverse health effect of acidic ultrafine particles (AUFPs) has been widely recognized in scientific societies. These particles mainly deposit on the surface by diffusion and so far there is no mature method for the measurement of airborne AUFPs. The purpose of this study was to develop a diffusion sampler (DS) with iron nanofilm detectors to effectively measure the number concentration and size distribution of airborne AUFPs in indoor and outdoor environments. The developed DS was made of stainless steel with a flat and rectangular channel with 1.0 mm height, 50 mm width, and 500 mm length. The iron nanofilm detectors were deployed on rectangular recesses inside the sampler at three different locations along the length of the channel to collect the ultrafine particles. The exposed detectors were then scanned using an atomic force microscope (AFM) to numerate and distinguish the AUFPs from the nonacidic UFPs. Prior to sampling, the semi-empirical equations for the diffusive deposition efficiency of particles at the different detector locations in the sampler were obtained on the basis of theoretical diffusive mechanism and modified by the experimental data using polystyrene latex (PSL) standard particles. After calibration, the DS C AFM method and a commercially available online measurement system, i.e., scanning mobility particle sizer (SMPS) incorporated with a condensation particle counter (CPC), were simultaneously used in a 4-week field measurement. Both methods showed very good agreement in terms of total particle number concentration and size distribution. The results indicate that the diffusion sampler is effective for the quantification of ambient acidic ultrafine particles.

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Section: Sampling Techniquementioning

confidence: 94%

Section: Validation Of the Diffusion Samplermentioning

confidence: 99%

Diffusion Sampler for Measurement of Acidic Ultrafine Particles in the Atmosphere

Wang

Guo

Chan

2014

Aerosol Science and Technology

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“…Previous reports stated that "As the height of the potential energy barrier increase, for a given value of the depth of the secondary minimum, the fraction of particles that coagulating in the primary minimum becomes negligible and secondary minimum coagulation dominates" [25]. In addition, the importance of reversible attachment of colloidal particles in secondary energy minimum has been well proved by the deposition and reentrainment through porous media [18,19]. Based on the discussion of coagulation mechanisms in the former section, patch coagulation and bridge connection are thought to prevail over charge neutralization when particle surfaces have charges of the same sign.…”

Section: Particle Aggregation Trapped At the Secondary Energy Minimummentioning

confidence: 99%

“…Chemical aspects of coagulation have been integrated with the model based on the chemical behaviors of soluble or insoluble hydroxide species, in these cases, the DLVO theory has generally been treated as a qualitative background for the coagulation model [3][4][5][6]17]. Other papers have described the efficiency of particle aggregation in water treatment by applying the DLVO principle with the secondary energy minimum, which have been mainly concerned with the water filtration process [18,19]. Few papers have applied the DLVO model quantitatively to this particle aggregation process when it follows charge-neutralization.…”

Section: Introductionmentioning

confidence: 99%

Distinct mechanisms of particle aggregation induced by alum and PACl: Floc structure and DLVO evaluation

Wang

et al. 2009

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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a b s t r a c tInteractions of silica microspheres were examined by light scattering in presence of alum and polyaluminum chloride (PACl) with various OH/Al ratios. The coagulation behaviors were investigated using different coagulant dosages at constant pH (6.5) and salt concentration (0.01 mol/L). Based on the measurement of size distribution and zeta potential, charge neutralization was proposed to be the primary coagulation step for all the coagulants while other distinct coagulation steps were also involved depending on in situ formed or preformed hydrolyzing products. Precipitate coverage and sweep flocculation were induced for alum, contrasted to polycation patch and bridge aggregation for PACl. Based on simplified DLVO theory, particle aggregation was explained in terms of interaction forces. It was demonstrated that PACl outperformed alum in particle agglomeration at lower concentration (1-2 mol/L), owing mainly to the considerable energy barrier reduction and deeper secondary minimum at longer distance induced by high positive polycations. The role of secondary minimum was found to be significant when secondary depth exceeded 12 kT. The interaction energy calculations coincided well with coagulation result for PACl, especially PACl22 with high content Al 13 . However, other interaction forces prevailed over the electrical repulsion for alum and PACl containing other aluminum species.

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“…Colloid filtration theory and DLVO theory are typically applied to the transport and attachment of nanoparticles to a collector surface. Diffusion is the dominant transport mechanism to the collector while the total particle-particle and particle-collector interaction energies are used as a predictor of nanoparticle stability, aggregation, and deposition onto a collector surface (30, 31, 44,49,63). Additionally, non-DLVO or extended DLVO interactions,…”

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confidence: 99%

Characterization of Nano-scale Aluminum Oxide Transport Through Porous Media

Norwood¹

2000

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Land application of biosolids has become common practice in the United States as an alternative to industrial fertilizers. Although nutrient rich, biosolids have been found to contain high concentrations of unregulated and/or unrecognized emerging contaminants (e.g., pharmaceuticals, personal care products) while containing a significant fraction of inorganic nano-scale colloidal materials such as oxides of iron, titanium, and aluminum.Given their reactivity and small size, there are many questions concerning the potential migration of these nano-sized colloidal materials through the soil column and into our surface and groundwater bodies. Transport of emerging pollutants of concern through the soil column, at minimum, is impacted by colloidal properties (e.g., chemical composition, shape, aggregation kinetics), solution chemistry (e.g., pH, ionic strength, natural organic matter), and water flow velocity. The purpose of this current research was to characterize the long-term transport behavior of aluminum oxide nanoparticles (Al 2 O 3 ) through a natural porous media with changes in pH, aqueous-phase concentration, pore-water velocity and electrolyte valence. Additionally, deposition rates during the initial stages of deposition were compared to several models developed based on colloid filtration theory and DLVO stability theory. Benchtop column laboratory experiments showed that, under environmentally relevant groundwater conditions, Al 2 O 3 nanoparticles are mobile through saturated porous media. Mobility increased under conditions in which the nanoparticles and porous media were of like charge (pH 9). Changes in linear pore water velocity, under these same high pH conditions, showed similar transport behavior with little mass retained in the system. Deposition is believed to be kinetically controlled at ii pH 9, as evidenced by the slightly earlier breakthrough as flow rate increased and was further supported by observed concentration effects on the arrival wave following several stop flows. While lower aqueous-phase concentrations resulted in significantly longer breakthrough times, the total mass retained in the system was found to be independent of concentration. Additionally, experimental deposition rate coefficients ( ), used to describe deposition kinetics under "clean bed" conditions, were similar across the aqueous-phase concentrations studied. The use of calcium chloride electrolyte solution in transport studies resulted in enhanced mobility relative to potassium chloride suggesting that changes in groundwater solution chemistry could impact mobility of contaminants associated with biosolids. Predicted deposition rate coefficients, using three different models, were found to under-or over-predict values relative to those experimentally determined values depending on the model. This current research has shown that nanocolloids associated with biosolids, specifically Al 2 O 3 , are mobile through saturated porous media. Given the ubiquity of nanocolloidal materials, particularly engineered n...

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Effect of particle size on collision efficiency in the deposition of Brownian particles with electrostatic energy barriers

Abstract: alue was nearly zero in the solid monolayer below the Tc. This means probably that the relatively short C14OH is removed easily from the fluid state of the monolayer above the Tc, although it can block the defects in the solid state monolayer.

Cited by 362 publications

References 0 publications

Diffusion Sampler for Measurement of Acidic Ultrafine Particles in the Atmosphere

Diffusion Sampler for Measurement of Acidic Ultrafine Particles in the Atmosphere

Distinct mechanisms of particle aggregation induced by alum and PACl: Floc structure and DLVO evaluation

Characterization of Nano-scale Aluminum Oxide Transport Through Porous Media

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