Distribution and attachment of metal ions to the pulp components in kr
aft pulps can affect the possibilities to achieve a metal ion profile
favourable for total chlorine free bleaching. By enrichment and analys
is of different morphological fractions of the pulp, such as material
from the fibre surface and ray cells, the metal ion distribution (Fe,
Cu, Mn, Mg and Ca) in a commercial unbleached softwood kraft pulp (kap
pa number 32) was investigated. Material removed from the surface of u
nbleached kraft fibres and the fraction containing the ray cells were
found to have a considerably higher metal ion content than the rest of
the pulp. There was good correlation between the content of manganese
and calcium and the content of lignin and carboxy groups. Distributio
n patterns of metal ions in the pulp appear to resemble those found in
the wood. The metal profile in the pulp was studied also following ED
TA treatment. Metal ions remaining in the pulp after the EDTA treatmen
t were still unevenly distributed, with high levels in the surface mat
erial and the ray cell enriched fraction.