Collision frequencies of fractal aggregates with small particles by differential sedimentation

被引:126
作者
Li, XY [1 ]
Logan, BE [1 ]
机构
[1] UNIV ARIZONA,DEPT ENVIRONM CHEM & ENGN,TUCSON,AZ 85721
关键词
D O I
10.1021/es960771w
中图分类号
X [环境科学、安全科学];
学科分类号
08 ; 0830 ;
摘要
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 mu m) in a Jar-test (paddle-mixing) device. The collision rates between these fractal aggregates (200-100 mu m) and small (1.48 mu m) 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 <0.25% 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.
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页码:1229 / 1236
页数:8
相关论文
共 32 条
[1]  
ADLER PM, 1981, J COLLOID INTERF SCI, V81, P531, DOI 10.1016/0021-9797(81)90434-3
[2]   USE OF COLLOID FILTRATION THEORY IN MODELING MOVEMENT OF BACTERIA THROUGH A CONTAMINATED SANDY AQUIFER [J].
BOUWER, EJ ;
RITTMANN, BE .
ENVIRONMENTAL SCIENCE & TECHNOLOGY, 1992, 26 (02) :400-401
[3]  
Camp T.R., 1943, J. Boston Society of Civil Engineers, V30, P219
[4]   FLUID-MECHANICS AND FRACTAL AGGREGATES [J].
CHELLAM, S ;
WIESNER, MR .
WATER RESEARCH, 1993, 27 (09) :1493-1496
[5]  
DULLIEN FAL, 1994, POROUS MEDIA FLUID T, P286
[6]  
FRIEDLANDER SK, 1977, SMOKE DUST HAZE, P194
[7]   THE (RELATIVE) INSIGNIFICANCE OF G IN FLOCCULATION [J].
HAN, MY ;
LAWLER, DF .
JOURNAL AMERICAN WATER WORKS ASSOCIATION, 1992, 84 (10) :79-91
[8]  
HAWLEY N, 1982, J GEOPHYS RES-OCEANS, V87, P9489, DOI 10.1029/JC087iC12p09489
[9]   RECONCILING AGGREGATION-THEORY WITH OBSERVED VERTICAL FLUXES FOLLOWING PHYTOPLANKTON BLOOMS [J].
HILL, PS .
JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS, 1992, 97 (C2) :2295-2308
[10]   THE POTENTIAL ROLE OF LARGE, FAST-SINKING PARTICLES IN CLEARING NEPHELOID LAYERS [J].
HILL, PS ;
NOWELL, ARM ;
MCCAVE, IN .
PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES, 1990, 331 (1616) :103-117