The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.
Aalto

Surface Interactions in TMP Process Waters

Tekla Tammelin

Dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Department of Forest Products Technology for public examination and debate in Auditorium PUU 2 at Helsinki University of Technology (Espoo, Finland) on the 1st of December, 2006, at 12 noon.

Overview in PDF format (ISBN 951-22-8483-9)   [1767 KB]
Dissertation is also available in print (ISBN 951-22-8482-0)

Abstract

The overall goal of the thesis was to better understand on a molecular level different interactions present in the wet-end of the paper machine that uses thermomechanical (TMP) pulp. The work is divided into three parts:

  1. Introduction of the QCM-D technique to papermaking applications (polyelectrolyte adsorption studies)
  2. Development of model surfaces for cellulose, lignin and wood extractives for adsorption studies
  3. Adsorption studies of dissolved hemicelluloses and colloidal wood extractives on the model surfaces

The work was started by studying the adsorption of cationic starch onto the oppositely charged silica surface with the quartz crystal microbalance with dissipation (QCM-D). The aim of these preliminary adsorption studies was to better understand the electrostatic interactions between polyelectrolyte and surface, the factors which have influence on adsorption and the structure and physical properties of the adsorbed layer. The results were in accordance with the well-known theories of the polyelectrolyte adsorption.

In order to investigate the surface interactions in the TMP process waters, model surfaces for cellulose, lignin and wood extractives were prepared. In this way the interactions between the components originating from the pulp (dissolved and colloidal substances) and the fibrous material could be systematically studied. Raw materials were chosen so that they represent the main components present in a papermaking stock containing TMP. Atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) were used to investigate the morphology and chemistry of the model surfaces.

Finally, the adsorption of dissolved hemicelluloses and colloidal extractives on different fiber components were studied with the QCM-D. The aim was to clarify how colloidal resin and dissolved substances interact and how these interactions depend on e.g. peroxide bleaching of the TMP and ionic strength. It was found that dissolved hemicelluloses adsorb at the largest on cellulose. They also adsorbed on extractives but there was no significant affinity towards lignin. Adsorption increased with increasing ionic strength on cellulose and on extractives. Colloidal extractives preferentially adsorbed on cellulose when only electrostatically stabilized. The dissolved hemicelluloses created a steric hindrance against colloidal adsorption on all surfaces, but the effect was most pronounced on cellulose. The adsorption of colloids increased with increasing ionic strength for almost all systems. On the basis of the fundamental surface studies, some practical observations achieved from the experiments with the fine material could be clarified.

This thesis consists of an overview and of the following 5 publications:

  1. Tammelin, T., Merta, J., Johansson, L.-S. and Stenius, P. (2004) Viscoelastic properties of cationic starch adsorbed on quartz studied by QCM-D. Langmuir 20: 10900-10909.
  2. Tammelin, T., Saarinen, T., Österberg, M. and Laine, J. (2006) Preparation of Langmuir/Blodgett-cellulose surfaces by using horizontal dipping procedure. Application for polyelectrolyte adsorption studies performed with QCM-D. Cellulose 13: 519-535.
  3. Tammelin, T., Österberg, M., Johansson, L.-S. and Laine, J. (2006) Preparation of lignin and extractive model surfaces by using spincoating technique – Application for QCM-D studies. Nordic Pulp and Paper Research Journal 21: 444-450.
  4. Tammelin, T., Johnsen, I. A., Österberg, M., Stenius, P. and Laine, J. (2006) Adsorption of colloidal extractives and dissolved hemicelluloses on thermomechanical pulp fiber components studied by QCM-D. Nordic Pulp and Paper Research Journal, accepted.
  5. Johnsen, I. A., Stenius, P., Tammelin, T., Österberg, M., Johansson, L.-S. and Laine, J. (2006) The influence of dissolved substances on resin adsorption to TMP fine material. Nordic Pulp and Paper Research Journal, accepted.

Keywords: adsorption, colloidal extractives, dissolved hemicelluloses, model surfaces, AFM, TMP, QCM-D, XPS

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© 2006 Helsinki University of Technology

Last update 2011-05-26