Improved dewatering behaviour of clay minerals dispersions via interfacial chemistry and particle interactions optimization

McFarlane, Angus, Bremmell, Kristen and Addai-Mensah, Jonas (2006) Improved dewatering behaviour of clay minerals dispersions via interfacial chemistry and particle interactions optimization. Journal of Colloid and Interface Science, 293 1: 116-127. doi:10.1016/j.jcis.2005.06.034


Author McFarlane, Angus
Bremmell, Kristen
Addai-Mensah, Jonas
Title Improved dewatering behaviour of clay minerals dispersions via interfacial chemistry and particle interactions optimization
Journal name Journal of Colloid and Interface Science   Check publisher's open access policy
ISSN 0021-9797
1095-7103
Publication date 2006-01-01
Year available 2005
Sub-type Article (original research)
DOI 10.1016/j.jcis.2005.06.034
Volume 293
Issue 1
Start page 116
End page 127
Total pages 8
Place of publication Maryland Heights, MO, United States
Publisher Academic Press
Language eng
Abstract Orthokinetic flocculation of clay dispersions at pH 7.5 and 22 °C has been investigated to determine the influence of interfacial chemistry and shear on dewatering and particle interactions behavior. Modification of pulp chemistry and behavior was achieved by using kaolinite and Na-exchanged (swelling) smectite clay minerals, divalent metal ions (Ca(II), Mn(II)) as coagulants and anionic polyacrylamide copolymer (PAM A) and non-ionic polyacrylamide homopolymer (PAM N) as flocculants. The pivotal role of shear, provided by a two-blade paddle impeller, was probed as a function of agitation rate (100–500 rpm) and time (15/60 s). Particle zeta potential and adsorption isotherms were measured to quantify the interfacial chemistry, whilst rheology and cryogenic SEM were used to investigate particle interactions and floc structure and aggregate network, respectively. Osmotic swelling, accompanied by the formation of “honeycomb” particle network structure and high yield stress, was produced by the Na-exchanged smectite, but not kaolinite, dispersions. Dispersion of the clay particles in 0.05 M Ca(II) or Mn(II) solution led to a marked reduction in particle zeta potential, complete suppression of swelling, honeycomb network structure collapse and a concomitant reduction in shear yield stress of smectite pulps. Optimum conditions for improved, orthokinetic flocculation performance of negatively charged clay particles, reflecting faster settling flocs comprised (i) coagulation, (ii) moderate agitation rate, (iii) shorter agitation time, and (iv) anionic rather than non-ionic PAM. The optimum dewatering rates were significantly higher than those produced by standard, manual-mixing flocculation techniques (plunging and cylinder inversion) commonly used in industry for flocculant trials. The optimum flocculation conditions did not, however, have a significant impact on the final sediment solid content of 20–22 wt%. Further application of shear to pre-sedimented pulps improved consolidation by 5–7 wt% solid. Higher shear yield stresses and greater settling rates were displayed by PAM A based than PAM N based pulps and this is attributed to the former's more expanded interfacial conformation and greater clay particles bridging ability. It appears that the intrinsic clay particles' physico-chemical properties and interactions limit compact pulp consolidation.
Keyword Smectite
Kaolinite
Clay mineral flocculation
Polyacrylamide
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ
Additional Notes Available online 20 July 2005

Document type: Journal Article
Sub-type: Article (original research)
Collection: Julius Kruttschnitt Mineral Research Centre Publications
 
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Created: Tue, 09 Aug 2011, 15:24:04 EST by Karen Holtham on behalf of Julius Kruttschnitt Mineral Research Centre