Adsorption of colloidal extractives and dissolved hemicelluloses on thermomechanical pulp fiber components studied by QCM-D

The primary aim of this work was to obtain a better understanding of the colloidal interactions in the wet-end of paper machines that use thermomechanical pulp. Adsorption of colloidal extractives and dissolved hemicelluloses derived from Norway spruce (Picea abies) on model surfaces of cellulose, lignin and extractives was studied, using a quartz crystal micro-balance with dissipation (QCM-D), The goal of the study was to clarify how colloidal extractives and dissolved hemicelluloses interact with fiber components and how these interactions depend on e.g. peroxide bleaching and ionic strength. Dissolved hemicelluloses adsorbed most extensively on cellulose. They also adsorbed on extractives but there was no significant affinity towards lignin. Adsorption on cellulose and extractives increased with increasing ionic strength. Adsorption of electrostatically stabilized colloidal extractives was the largest on cellulose and extensive also on lignin. It increased on both surfaces with increasing ionic strength. These colloids did not adsorb on the extractive surface. The adsorption of colloidal extractives on cellulose and lignin decreased when were sterically stabilized with dissolved hemicelluloses. On the other hand, the sterically stabilized colloids seemed to adsorb on extractives. If the dissolved hemicelluloses were adsorbed also on substrate surfaces, the subsequent adsorption of sterically stable colloidal dispersion was almost completely prevented. This effect was most pronounced on cellulose.