Fate of metal cations in the kraft pulping process modified by phosphonates

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Abstract

Metal cation exchange with unbleached fibers was investigated using hardwood kraft pulps produced with phosphonate addition in the digester. Metal contents and their sorption by the dissolved kraft lignin in the black liquor were also quantified. Ion exchange constants for the calcium-sodium pair were determined. Reductions of Fe, Mn and Zn are most likely responsible for the brightness improvement of resulting pulps as well as their beneficial responses in subsequent bleaching. Metal-ions especially calcium on fibers are significantly decreased by-phosphonates addition in cooking; they eventually enter the black liquor and form soluble phosphonate-cation groups. Approximately 800-1000ppm of calcium was retained on fibers while less than 67ppm were found in precipitated kraft lignin. The overall solids content within the cooking system was increased by 0.6-1.3%.

Original languageEnglish (US)
Title of host publication2003 TAPPI Fall Technical Conference
Subtitle of host publicationEngineering, Pulping and PCE and I, Proceedings
Pages373-392
Number of pages20
StatePublished - Dec 1 2003
Event2003 TAPPI Fall Technical Conference: Engineering, Pulping and PCE and I - Chicago, IL, United States
Duration: Oct 26 2003Oct 30 2003

Other

Other2003 TAPPI Fall Technical Conference: Engineering, Pulping and PCE and I
CountryUnited States
CityChicago, IL
Period10/26/0310/30/03

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    Li, W., & Tschirner, U. W. (2003). Fate of metal cations in the kraft pulping process modified by phosphonates. In 2003 TAPPI Fall Technical Conference: Engineering, Pulping and PCE and I, Proceedings (pp. 373-392). [18-1]