Dynamics of polymer-induced hetero-flocculation of wood fibres and fines

The kinetics of polymer-induced hetero-flocculation of wood fibres and fine s was investigated. A polymer layer (cationic poly(acrylamide)) was deposit ed on either the fibres or the fines, and the fines concentration was follo wed after mixing both components. It is shown that the flocculation state i s only transient. This is explained by a redistribution of polymer between surfaces upon particle detachment, which leads to a re-stabilisation of the system. Simultaneous particle deposition, particle detachment and polymer transfer determine the apparent particle detachment rate. The detachment ra te is strongly shear-dependent, and the resulting polymer layers after redi stribution have a reduced bridging ability compared to the fresh layers. (C ) 2000 Elsevier Science B.V. All rights reserved.