Desorption of metal ions from kraft pulps. Part 1. Chelation of hardwood and softwood kraft pulp with EDTA

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    Abstract

    Chelation of unbleached and oxygen bleached hardwood and softwood kraft pulps with EDTA was studied. The main focus was on the desorption of magnesium, manganese, and iron due to their impact in TCF-bleaching. Desorption of other metal ions present were also studied in order to get an over-all estimation of the metal ion concentrations and their desorption during chelation. By using the concept of side reaction coefficients, an estimation of the chelating strength of EDTA at different pH can be made. Metal ion concentrations were determined by DCP-AES and ICP-MS techniques. Mn, Zn, and Cd were the metal ions that could almost completely be chelated with EDTA. Most of the metal ions were found to be desorbed from the pulps at low pH values by ion exchange with hydrogen ions. With EDTA chelation 50 to 70% of the iron was desorbed. By EDTA chelation the highest Mg/Mn concentration ratios were obtained in the pH range 4 to 6. For oxygen-bleached softwood pulp the ratio was over 7000. Our study showed that both unbleached and bleached pulps can quite successfully be chelated by EDTA.
    Original languageUndefined/Unknown
    Pages (from-to)206–226
    Number of pages21
    JournalBioResources
    Volume5
    Issue number1
    Publication statusPublished - 2010
    MoE publication typeA1 Journal article-refereed

    Keywords

    • Chelation
    • Desorption
    • EDTA
    • Hardwood kraft pulp
    • Metal ions
    • Side reaction coefficients
    • Softwood kraft pulp

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