Adsorption of Ca~(2+) in high-yield kraft and TCF bleached pulps

摘要

The distribution coefficient of Ca~(2+) in slurries of unbleached and bleached kraft pulps were determined and compared with predictions obtained from the Towers and Scallan's model. It was apparent that the Towers and Scallan's model predicted the distribution coefficient of Ca~(2+) in the bleached pulp slurries very well. However the model needed to be modified, by taking into account the presence of both carboxylic and phenolic groups, for better prediction of the distribution coefficients in the unbleached pulp slurries. This modification improved the prediction over the pH range of 2-10. When pH exceeded 10 the modified model underestimated the distribution coefficient due probably to the presence of at least another ionisable group with a high pK_a.