Study on metal ion affinities to oxygen delignified hardwood kraft pulp by a column chromatographic method

摘要

Metal ions have generally negative effects in closed cycle pulp mill operations and totally chlorine free bleaching. To study the binding of different metal ions to oxygen bleached hardwood pulp in more detail an ion exchange model was applied. By using a column chromatographic method even rather small differences in metal ion affinities could be detected. A method of competition was used in the experiments with an excess of respective metal ions in comparison to the total binding capacity of the pulp samples. The following series with decreasing affinities to the pulp studied was obtained:Fe~(3+) Pb~(2+) Cu~(2+) Cd~(2+) >Zn~(2+) > Ba~(2+) > Ca~(2+) > Mn~(2+) > Fe~(2+) > Sr~(2+) > Mg~(2+) > K~+ ≈ Rb~+ >Na~+ Oxygen bleached hardwood pulp thus shows a clear selectivity for different metal ions. Of divalent metal ions lead and copper are most strongly bound. Trivalent iron showed a completely different sorption behavior compared to the other metal ions studied in this work.