Microstructure, rheology and dewatering behaviour of smectite dispersions during orthokinetic flocculation

McFarlane, A., Bremmell, K. and Addai-Mensah, J. (2005). Microstructure, rheology and dewatering behaviour of smectite dispersions during orthokinetic flocculation. In: Tim Napier-Munn, JKMRC International Student Conference 2004, Brisbane, Australia, (1173-1182). September 2004. doi:10.1016/j.mineng.2005.06.013

Author McFarlane, A.
Bremmell, K.
Addai-Mensah, J.
Title of paper Microstructure, rheology and dewatering behaviour of smectite dispersions during orthokinetic flocculation
Conference name JKMRC International Student Conference 2004
Conference location Brisbane, Australia
Conference dates September 2004
Journal name Minerals Engineering   Check publisher's open access policy
Place of Publication Kidlington, Oxford, United Kingdom
Publisher Pergamon
Publication Year 2005
Sub-type Fully published paper
DOI 10.1016/j.mineng.2005.06.013
ISSN 0892-6875
Editor Tim Napier-Munn
Volume 18
Issue 12
Start page 1173
End page 1182
Total pages 10
Language eng
Formatted Abstract/Summary
The influence of high molecular weight (>7.5 × 106 Da) polyacrylamide (PAM) flocculant type (anionic vs non-ionic), solution speciation (KNO3 + CaCl2 vs KNO3) and shear on microstructure, rheology and the dewatering behaviour of Na-exchanged smectite clay dispersions has been investigated under orthokinetic flocculation conditions at pH 7.5. Massive osmotic swelling, accompanied by high shear yield stress and non-settling behaviour, were displayed by dispersions prepared in 10−3 M KNO3 background electrolyte and to which 0.05 M CaCl2 was subsequently added. Prior clay dispersion in CaCl2-based solution however led to rapid exchange of Ca2+ with Na+ in the clay and suppression of swelling which reflected in low yield stress, dramatic reduction in particle zeta potential and marginally improved dewaterability. Cryo-SEM image analysis indicated the presence of highly networked “honeycomb” structure in the swelling clay pulps and loosely networked, chain-like structure in non-swelling dispersions. Dewatering of suppressed swelling pulps indicated optimum conditions for orthokinetic flocculation, dependent upon flocculant structure type and shear intensity, which strongly influenced the settling rate but not the low pulp consolidation (not, vert, similar21 wt% solid) behaviour. Under optimum conditions, anionic PAM produced significantly faster settling flocs than non-ionic PAM at up to 500 g polymer t−1 solid. Post-sedimentation shear action markedly improved pulp solid loading by 5–7 wt%, independent of PAM type. Anionic PAM flocculated pulps displayed 25% higher yield stresses than non-ionic PAM-based pulps. Upon shear however, the yield stress of the former decreased dramatically to values lower than those of the latter, indicating that anionic PAM-based flocs structures were less robust, a finding which is consistent with cryo-SEM imaging.
Keyword Waste processing
Mineral processing
Particle morphology
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ

Document type: Conference Paper
Collection: Julius Kruttschnitt Mineral Research Centre Publications
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Created: Tue, 09 Aug 2011, 15:38:45 EST by Karen Holtham on behalf of Julius Kruttschnitt Mineral Research Centre