Collision frequencies of fractal aggregates with small particles by differential sedimentation

Xiaoyan Li, Bruce Ernest Logan

Research output: Contribution to journalArticle

120 Citations (Scopus)

Abstract

Two groups of aggregates with fractal dimensions of 1.81 ± 0.09 and 2.33 ± 0.07 were generated by coagulation of latex microspheres (2.84 μm) in a Jar-test (paddle-mixing) device. The collision rates between these fractal aggregates (200-1000 μm) and small (1.48μm) particles were measured for individual aggregates that had settled through a suspension of the small particles. Aggregate permeabilities calculated from measured settling velocities were 3 orders of magnitude greater than predicted by a permeability model based on a homogeneous distribution of primary particles within the aggregates. Collision frequencies were 1 order of magnitude higher than predicted by a curvilinear model and about 2 orders of magnitude lower than predicted by a rectilinear collision model. The capture efficiencies of small particles by settling aggregates were <0.2% based on the total volume of water swept out by an aggregate. Fluid collection efficiencies, collision frequencies, and particle capture efficiencies of the fractal aggregates decreased with the magnitude of fractal dimensions. A fractal permeability model was developed by modifying the Brinkman correlation to describe the permeability as a function of aggregate size. This model was used in conjunction with a filtration model to predict capture rates and capture efficiencies of small particles by settling fractal aggregates. Based on these experiments and models, it is argued that the high aggregate permeabilities and the low overall particle capture efficiencies of fractal aggregates can be explained by flow through macropores formed between large clusters within the aggregates.

Original languageEnglish (US)
Pages (from-to)1229-1236
Number of pages8
JournalEnvironmental Science and Technology
Volume31
Issue number4
DOIs
StatePublished - Apr 1 1997

Fingerprint

Sedimentation
Fractals
collision
sedimentation
permeability
Fractal dimension
particle
aggregate size
settling velocity
macropore
Latex
coagulation
Coagulation
Microspheres
Suspensions

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Environmental Chemistry

Cite this

@article{01e2c3ab37174f91b3c0998186bf3752,
title = "Collision frequencies of fractal aggregates with small particles by differential sedimentation",
abstract = "Two groups of aggregates with fractal dimensions of 1.81 ± 0.09 and 2.33 ± 0.07 were generated by coagulation of latex microspheres (2.84 μm) in a Jar-test (paddle-mixing) device. The collision rates between these fractal aggregates (200-1000 μm) and small (1.48μm) particles were measured for individual aggregates that had settled through a suspension of the small particles. Aggregate permeabilities calculated from measured settling velocities were 3 orders of magnitude greater than predicted by a permeability model based on a homogeneous distribution of primary particles within the aggregates. Collision frequencies were 1 order of magnitude higher than predicted by a curvilinear model and about 2 orders of magnitude lower than predicted by a rectilinear collision model. The capture efficiencies of small particles by settling aggregates were <0.2{\%} based on the total volume of water swept out by an aggregate. Fluid collection efficiencies, collision frequencies, and particle capture efficiencies of the fractal aggregates decreased with the magnitude of fractal dimensions. A fractal permeability model was developed by modifying the Brinkman correlation to describe the permeability as a function of aggregate size. This model was used in conjunction with a filtration model to predict capture rates and capture efficiencies of small particles by settling fractal aggregates. Based on these experiments and models, it is argued that the high aggregate permeabilities and the low overall particle capture efficiencies of fractal aggregates can be explained by flow through macropores formed between large clusters within the aggregates.",
author = "Xiaoyan Li and Logan, {Bruce Ernest}",
year = "1997",
month = "4",
day = "1",
doi = "10.1021/es960771w",
language = "English (US)",
volume = "31",
pages = "1229--1236",
journal = "Environmental Science & Technology",
issn = "0013-936X",
publisher = "American Chemical Society",
number = "4",

}

Collision frequencies of fractal aggregates with small particles by differential sedimentation. / Li, Xiaoyan; Logan, Bruce Ernest.

In: Environmental Science and Technology, Vol. 31, No. 4, 01.04.1997, p. 1229-1236.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Collision frequencies of fractal aggregates with small particles by differential sedimentation

AU - Li, Xiaoyan

AU - Logan, Bruce Ernest

PY - 1997/4/1

Y1 - 1997/4/1

N2 - Two groups of aggregates with fractal dimensions of 1.81 ± 0.09 and 2.33 ± 0.07 were generated by coagulation of latex microspheres (2.84 μm) in a Jar-test (paddle-mixing) device. The collision rates between these fractal aggregates (200-1000 μm) and small (1.48μm) particles were measured for individual aggregates that had settled through a suspension of the small particles. Aggregate permeabilities calculated from measured settling velocities were 3 orders of magnitude greater than predicted by a permeability model based on a homogeneous distribution of primary particles within the aggregates. Collision frequencies were 1 order of magnitude higher than predicted by a curvilinear model and about 2 orders of magnitude lower than predicted by a rectilinear collision model. The capture efficiencies of small particles by settling aggregates were <0.2% based on the total volume of water swept out by an aggregate. Fluid collection efficiencies, collision frequencies, and particle capture efficiencies of the fractal aggregates decreased with the magnitude of fractal dimensions. A fractal permeability model was developed by modifying the Brinkman correlation to describe the permeability as a function of aggregate size. This model was used in conjunction with a filtration model to predict capture rates and capture efficiencies of small particles by settling fractal aggregates. Based on these experiments and models, it is argued that the high aggregate permeabilities and the low overall particle capture efficiencies of fractal aggregates can be explained by flow through macropores formed between large clusters within the aggregates.

AB - Two groups of aggregates with fractal dimensions of 1.81 ± 0.09 and 2.33 ± 0.07 were generated by coagulation of latex microspheres (2.84 μm) in a Jar-test (paddle-mixing) device. The collision rates between these fractal aggregates (200-1000 μm) and small (1.48μm) particles were measured for individual aggregates that had settled through a suspension of the small particles. Aggregate permeabilities calculated from measured settling velocities were 3 orders of magnitude greater than predicted by a permeability model based on a homogeneous distribution of primary particles within the aggregates. Collision frequencies were 1 order of magnitude higher than predicted by a curvilinear model and about 2 orders of magnitude lower than predicted by a rectilinear collision model. The capture efficiencies of small particles by settling aggregates were <0.2% based on the total volume of water swept out by an aggregate. Fluid collection efficiencies, collision frequencies, and particle capture efficiencies of the fractal aggregates decreased with the magnitude of fractal dimensions. A fractal permeability model was developed by modifying the Brinkman correlation to describe the permeability as a function of aggregate size. This model was used in conjunction with a filtration model to predict capture rates and capture efficiencies of small particles by settling fractal aggregates. Based on these experiments and models, it is argued that the high aggregate permeabilities and the low overall particle capture efficiencies of fractal aggregates can be explained by flow through macropores formed between large clusters within the aggregates.

UR - http://www.scopus.com/inward/record.url?scp=0030994796&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0030994796&partnerID=8YFLogxK

U2 - 10.1021/es960771w

DO - 10.1021/es960771w

M3 - Article

VL - 31

SP - 1229

EP - 1236

JO - Environmental Science & Technology

JF - Environmental Science & Technology

SN - 0013-936X

IS - 4

ER -