1ADSORPTION OF MODEL COLLOIDAL EXTRACTIVES TO DIFFERENT TYPES OF FINES.

The ability of different types of fines to adsorb colloidal extractives and whether this adsorption is influenced by pH and the addition of NaCl, have been measured. In order to produce the different fines, chips from Norway spruce were refined in a pilot refiner. This was executed four successive times, producing different types of fines. Most of the fines were removed from the pulp by washing before further refining. The fines were washed and centrifuged before the adsorption measurements. A colloidal dispersion of extractives was produced by extracting TMP with acetone, and rapidly mixing this extract with water. After the acetone had been removed, the colloidal dispersion was added to the fines and the adsorption isotherms were measured. Below pH 5 there was clear adsorption of the colloids to the fines, which was not seen between pH 5 and 8. The adsorption at pH 3 was strongly influenced by the addition of NaCl. A rough estimation of the specific surface of the fines indicated that the different fines had similar abilities to adsorb the colloidal wood resin per square meter