Sorption of metal ions to untreated, alkali-treated and peroxide-bleached TMP

A1 Originalartikel i en vetenskaplig tidskrift (referentgranskad)


Interna författare/redaktörer


Publikationens författare: Pingping Su, Kim Granholm, Andrey Pranovich, Leo Harju, Bjarne Holmbom, Ari Ivaska
Förläggare: SPRINGER
Publiceringsår: 2010
Tidskrift: Cellulose
Tidskriftsakronym: CELLULOSE
Volym: 17
Nummer: 5
Artikelns första sida, sidnummer: 1033
Artikelns sista sida, sidnummer: 1044
Antal sidor: 12
ISSN: 0969-0239
eISSN: 1572-882X


Abstrakt

Knowledge about how different metal ions are bound to pulp fibers is very important for optimal metal management in pulping processes. A column chromatographic method was used to assess the differences in affinity of 14 metal ions to untreated, alkali-treated and peroxide-bleached thermomechanical pulp (TMP). A method of competition between cations in the column chromatographic experiments was used in the sorption experiments, with an excess of each metal ion compared to the total capacity of the pulp studied. The method is very sensitive and even small differences in affinities can be detected. By combining the results from sorption experiments with four different metal ion mixtures the following order of affinity was obtained: Pb(2+) a parts per thousand << Cu(2+) a parts per thousand << Cd(2+) > Zn(2+) > Ni(2+) > Ba(2+) > Ca(2+) > Mn(2+) > Sr(2+) > Mg(2+) a parts per thousand << Rb(+) a parts per thousand K(+) > Na(+) > Li(+). All three types of pulps showed the same affinity order. Lead and copper ions were clearly most strongly bound to the pulp fibers. Within the alkali and alkaline earth metal groups the differences in affinity were quite small. The sorption of metal ions to pulp fibers takes place mainly by complexation, where the divalent metal ions are coordinated to functional groups (acid groups) in the fiber phase. Protonation constants and concentrations of acid groups were determined by potentiometric titration. A model with two carboxyl groups and two phenolic hydroxyl groups satisfied best the experimental data. By treatment with alkali and peroxide new acid groups were created and the total binding capacity of hydrogen ions increased from 137 mu eq/g for untreated pulp to 187 and 228 mu eq/g for alkali-treated and peroxide-treated pulp, respectively.


Nyckelord

Affinity, Functional groups, Mechanical pulp, Metal ions, Sorption, Titration

Senast uppdaterad 2019-14-12 vid 03:41