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Effects of polyelectrolyte characteristics and flocculation conditions on fine particle floc properties
YKI – Ytkemiska institutet.
YKI – Ytkemiska institutet.
1993 (Engelska)Ingår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 8, s. 153-159, 175Artikel i tidskrift (Refereegranskat)
Abstract [en]

Polystyrene latex was flocculated with cationic polyelectrolytes of different charge densities at low ionic strength and the effects of different flocculation conditions were studied. The flocs were characterized in an equipment with which the flocculation kinetics, the floc structure, the shear resistance and the ability for reflocculation after high shear can be studied in a single experiment. The structure was further investigated by SEM on freezedried flocs. With low charge density polymers the flocs had good shear resistance but limited ability to reflocculate after high shear. They consisted of compact microflocs connected into more open macrostructures and were formed by a bridging mechanism. Best floc properties seemed to be obtained with relatively mild stirring conditions during the initial flocculation. With somewhat higher charge density (≈10 %) a transition in mechanism was indicated since best shear strength and reflocculation was obtained with high intensity stirring during the initial flocculation. With medium charge density polymers the shear strength was lower and less dependent on the initial stirring rate. The size of the initial flocs was strongly decreased by in-creasing initial mixing intensity. On the other hand, the reflocculation was better than with low charge density polymers, and it also improved with increasing initial stirring rate. The flocculation was mainly due to charge neutralization with limited contribution of bridging and electrostatic attractions in the total attractive force. With high charge density polymers the shear resistance was somewhat better than for medium charged polymers and high initial stirring intensity seemed to be favourable also in this case. The good reflocculation however, seemed to depend on the initial stirring intensity in a non-monotonous way. The structure of the flocs had voids on all length scales because of a flocculation mechanism with strong and close contacts between the primary particles.

Ort, förlag, år, upplaga, sidor
1993. Vol. 8, s. 153-159, 175
Nyckelord [en]
Flocs, Flocculation, Stirring, Cationic compounds, Synthetic polymers, Polyelectrolytes
Nationell ämneskategori
Naturvetenskap
Identifikatorer
URN: urn:nbn:se:ri:diva-27355OAI: oai:DiVA.org:ri-27355DiVA, id: diva2:1054359
Anmärkning
A801Tillgänglig från: 2016-12-08 Skapad: 2016-12-08 Senast uppdaterad: 2017-11-29Bibliografiskt granskad

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