Study on desorption of Mn, Fe, and Mg from TMP and evaluation of the complexing strength of different chelating agents using side reaction coefficients 10(th) EWLP, Stockholm, Sweden, August 25-28, 2008

Kim Granholm, Su PP, Leo Harju, Ari Ivaska

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    Chelation of thermomechanical pulp (TMP) was studied in this work. The desorption of Mn, Fe, and Mg due to their impact on peroxide bleaching was investigated. The desorption experiments were performed with EDTA, citric acid, oxalic acid, and formic acid as chelating agents at different pH. Chelation experiments with EDTA were carried out at pH 3-11. Sodium dithionite was used as the reducing agent in studying chelation with EDTA in a reducing environment. Mn was very effectively desorbed with EDTA from TMP at pH < 10 and the reducing environment further improved the removal of all the studied metal ions from TMP with EDTA. Citric acid also removed Mn effectively from TMP at pH 5. The thermodynamic stability constants of different metal chelates do not present the correct picture of how strongly the metal ions are bound by the chelating agents in different conditions. But by means of the side reaction coefficients (alpha(M(L))-coefficients) it is also theoretically possible to evaluate and compare the real binding strengths between the metal ions and different chelating agents at varying pH values and other solution conditions. In this study, a theory is given for the calculation of side reaction coefficients. Values of the alpha(M(L))-coefficients, for the pH range 0-14, are presented for EDTA, DTPA, and also for some other new potential environmentally friendly chelating agents.
    Original languageUndefined/Unknown
    Pages (from-to)785–790
    Number of pages6
    Issue number6
    Publication statusPublished - 2009
    MoE publication typeA1 Journal article-refereed


    • chelation
    • citric acid
    • dithionite
    • EDTA
    • Fe
    • formic acid
    • metal ions
    • Mg
    • Mn
    • oxalic acid
    • pulp
    • side reaction coefficients
    • thermomechanical pulp (TMP)

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