Pre-treatment of the paper pulp in the bleaching process using biodegradable chelating agents

I. S. S. Pinto, O. S. Ascenso, Maria Teresa Barros, H. M. V. M. Soares

Research output: Contribution to journalArticlepeer-review

9 Citations (Scopus)


The aim of this work was to study the application of two biodegradable chelating agents, pyridine-2,6- dicarboxylic acid (PDA) and methylglycinediacetic acid (MGDA), in the treatment of the pulp, prior to hydrogen peroxide bleaching. Such compounds must remove transition metals (Mn, Fe and Cu) from pulp, that catalyze the degradation of hydrogen peroxide, and Ca, which is also problematic due to the formation of precipitates that accumulate in the equipment. Computer simulations were first performed to study the best conditions for metal complexation, and optimum pH was defined as 5–5.5 for PDA and 6.5–7 for MGDA. Metals removal from the pulp, as well as the subsequent bleaching process (Q-P1-Paa-P2), were tested experimentally, and performances were compared to ethylenediaminetetracetic acid (EDTA). PDA removed both Mn and Ca efficiently, leaving most Mg in the pulp after first chelation stage, while MGDA had a lower Ca removal, even using a higher pH and concentration. Residual hydrogen peroxide and kappa number after peroxide stages showed a similar bleaching efficiency between the studied compounds and EDTA.
Original languageEnglish
Pages (from-to)975-982
JournalInternational Journal of Environmental Science and Technology
Issue number3
Publication statusPublished - Mar 2015


  • Bleaching
  • Chelating agents
  • Methylglycinediacetic acid
  • Paper pulp
  • Pyridine-2,6-dicarboxylic acid (dipicolinic acid)


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