The flocculation efficiency of polydisperse polymer flocculants

Yan, Y. D., Glover, S. M., Jameson, G. J. and Biggs, S. (2004) The flocculation efficiency of polydisperse polymer flocculants. International Journal of Mineral Processing, 73 2-4: 161-175. doi:10.1016/S0301-7516(03)00071-1

Author Yan, Y. D.
Glover, S. M.
Jameson, G. J.
Biggs, S.
Title The flocculation efficiency of polydisperse polymer flocculants
Journal name International Journal of Mineral Processing   Check publisher's open access policy
ISSN 0301-7516
Publication date 2004-02-03
Year available 2003
Sub-type Article (original research)
DOI 10.1016/S0301-7516(03)00071-1
Open Access Status Not yet assessed
Volume 73
Issue 2-4
Start page 161
End page 175
Total pages 15
Place of publication Amsterdam, Netherlands
Publisher Elsevier BV
Language eng
Formatted abstract
The flocculation performance of three poly(acrylic acid) (PAA) samples (Mw=9×104, 2.5×105 and 1×106 g/mol) has been investigated. Colloidal alumina particles were used as a model system and tests were performed at pH 5. Using a single-component polyacid, it was found that the optimum dosage required to achieve supernatant clarity was similar between the 9×104 g/mol PAA (23 ppm) and 2.5×105 g/mol PAA (26 ppm), but increased dramatically with the 1×106 g/mol PAA (83 ppm). For the two lower molecular weight samples, flocculation occurs through a charge neutralisation mechanism. In contrast, polymer bridging is inferred to be the dominant flocculation mechanism for the high molecular weight sample. The flocculation performance of a polymer mixture, produced by blending the high and low molecular weight polyacids to give an average molecular weight of 2.5×105 g/mol, was also studied. Supernatant clarity from this system was found to be comparable to that from the single-component polyacid of the same (average) molecular weight. However, the optimum dosage required for the polymer mixture was about twice as much as that for the single-component reference polymer. The results suggest that for the polymer mixture no synergistic effects occur. Instead, analyses of aggregate sizes indicate an independent behaviour for the two polymers in the blend. We also examined re-suspension (under shear) and re-flocculation of the sediment formed in the initial flocculation experiments. For the three single-polymer systems, rapid re-flocculation after shear was seen for the two lower molecular weight samples suggesting a reversible aggregate breakage. For the high molecular weight sample, re-suspension resulted in the formation of a stable dispersion. This result was attributed to breakage of the high molecular weight polymer sample during re-suspension. In the case of the polymer mixture, rapid re-flocculation was again observed despite the presence of a large amount of the high molecular weight sample. This result may have important practical implications.
Keyword Flocculants
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ

Document type: Journal Article
Sub-type: Article (original research)
Collection: Faculty of Engineering, Architecture and Information Technology Publications
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