A Model to Describe the Settling Behavior of Fractal Aggregates

Tang, Patricia A.; Greenwood, J. C.; Raper, Judy A

doi:10.1006/jcis.2001.8028

Cited by 82 publications

(61 citation statements)

References 17 publications

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“…High D F means the primary particles in an aggregate are arranged compactly, while low D F results from large, highly branched and loosely bound structures. According to previous research, methods utilized to characterize the fractal dimension are mainly microscopy, light scattering, and settling techniques (Wu et al, 2002;Koen and Willy, 1997;Chakraborti et al, 2003;Tang et al, 2002).…”

Section: Fractal Dimensionmentioning

confidence: 99%

Characterization of kaolin flocs formed by polyacrylamide as flocculation aids

Zhu

et al. 2009

International Journal of Mineral Processing

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a b s t r a c t a r t i c l e i n f oAlthough the synthetic organic polymers have been widely applied as flocculant aids to improve solid-liquid separation efficiency, it is not very clear how the charge type and molecular weight of the polymers influence the characteristics of flocs. In this paper, floc characteristics, such as floc size, density, structure, strength and reversibility were investigated in details in terms of their response to the polyacrylamide (PAM) with different charge types and molecular weights. Laser light scattering, image analysis and settling technology were employed simultaneously. The results showed that floc size induced by anionic PAM with medium molecular weight (A130) and ultra high molecular weight (A115) was 419 µm and 438 µm respectively, correspondingly, floc size induced by cationic PAM with medium molecular weight (C448) and very high molecular weight (C498) was 731 µm and 796 µm. Meanwhile, floc fractal dimension was inversely proportional to polymer molecular weight and the values were between 1.91 and 2.40. In addition, floc density was affected by molecular weight of anionic PAM more dramatically than that of cationic PAM. For a given floc size, the density increased with molecular weight. Furthermore, flocs formed by cationic PAM showed much greater shear-resistant ability and reversibility than anionic PAM. Nevertheless, the poor reversibility of the flocs formed by high molecular weight was also observed. An explanation for the resultant floc characteristics was offered in terms of flocculation mechanisms.

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Section: Fractal Dimensionmentioning

confidence: 99%

Characterization of kaolin flocs formed by polyacrylamide as flocculation aids

Zhu

et al. 2009

International Journal of Mineral Processing

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“…At present, three common techniques for fractal dimension measurement have been developed, i.e. light scattering, settling and image analysis [12][13][14][15].…”

Section: Fractal Dimensionmentioning

confidence: 99%

Characterization of floc size, strength and structure under various coagulation mechanisms

et al. 2006

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Flocs generated by various coagulation mechanisms exhibit different size, strength and structure. The properties and fractal dimensions of flocs formed under three common coagulation mechanisms, i.e. charge neutralization, sweep and bridging, were investigated at various hydraulic conditions. The results showed that the floc size decreased with the increasing average velocity gradient G and the stable floc size exponent γ was of the following hierarchy: charge neutralization (0.6107) N sweep (0.5618) N bridging (0.3674). Furthermore, fractal dimensions of flocs were the highest when formed by sweep and the lowest when generated by bridging flocculation. The mass fractal dimensions measured by light scattering were between 2.0 and 3.0 and the floc strength was between 0.01 and 0.58 N m − 2 . An intrinsic unity of the relationship among floc size, fractal dimensions, floc strength under the three coagulation mechanisms was demonstrated.

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“…The Malvern Mastersizer has an array of photosensitive detectors at different angles between 0.01 • and 40.6 • that detect the light scattered by the sample. The determination of fractal dimension by use of SALLS has been well illustrated [14][15][16], so only a brief overview is given below.…”

Section: Floc Structural Analysismentioning

confidence: 99%

“…The total scattered light intensity I is a function of the scattering vector Q, where Q is the difference between the incident and scattered wave vectors of the radiation beam in the medium [14], which is given by Eq. (2).…”

Section: Floc Structural Analysismentioning

confidence: 99%

Effect of dosage strategy on Al-humic flocs growth and re-growth

Liu

et al. 2012

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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a b s t r a c tThe ability of flocs growth has a significant effect on the efficiency of solid/liquid separation during coagulation process. The growth and re-growth of flocs by one time or continuous dosage were explored at neutral pH, including one time and continuous additional dosage strategy after flocs breakage. The size of flocs formed by continuous dosage before breakage was much larger than the one formed by one time dosage. There was significant irreversibility of floc breakage when no additional coagulant was added. For the one with one time initial dosage strategy, the size of re-grown flocs by one time additional dosage was nearly the same as that before breakage. The re-grown flocs formed by continuous additional dosage were a little smaller than that formed by one time additional dosage. It definitely showed that the growth or connection of flocs was probably not determined by the flocs size distribution and fractal dimension, but by the surface activity of flocs. Additional dosage could improve flocs re-grown ability because the surface activity of broken flocs was repaired by adding new alum.

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A Model to Describe the Settling Behavior of Fractal Aggregates

Cited by 82 publications

References 17 publications

Characterization of kaolin flocs formed by polyacrylamide as flocculation aids

Characterization of kaolin flocs formed by polyacrylamide as flocculation aids

Characterization of floc size, strength and structure under various coagulation mechanisms

Effect of dosage strategy on Al-humic flocs growth and re-growth

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