Characterization of pulp and paper waters with off-line and on-line capillary electrophoresis

Heli Sirén, Raimo Kokkonen, Stella Rovio, Seppo Kauliomäki, Teemu Työppönen, Pertti Vastamäki, Heikki Leinonen

Research output: Chapter in Book/Report/Conference proceedingConference article in proceedingsScientificpeer-review

Abstract

The studies covered laboratory, pilot and industry scale instrumentation, method development and process sample measurements with various capillary electrophoresis (CE) instruments. The research started by modification of commercial CE apparatus for on-line sampling and on-line sample pre-treatment. Afterwards, the studies were performed with process-scale designed on-line CE systems. The instruments were used in on-line mode, even under industrial process conditions, when studying sulphur compounds at above 100 oC temperatures. The projects were challenging, since many of the analytes exhibit weakly acidic properties and some of them were only totally ionized in alkaline solutions. Direct UV detection of the analytes was achieved by in-capillary complex formation, but mainly the analytes were studied using indirect detection techniques. In on-line CE instrument, contactless conductivity detection (CCD) was used. The methods were capable for monitoring and determination of inorganic and organic compounds from different process waters. The tests we made by coupling the instruments in on-line with paper machines and in analyzing ions from the wet end waters. The technology and methodology could be used to monitor formaldehyde as the biocide chemical in wire washing and, in general, to observe process disturbances resulting from concentrations for periods between two weeks and one month at paper and pulp mills in Finland. As to the pulp samples, they were digested using sample preparation. The solution obtained from the procedure was analyzed. Mainly the interest was the metal ions in the pulp and the performance of the bleaching chemicals, but also amounts of carbohydrates in pulp cooking conditions. The studies with off-line and on-line techniques convinced that the ionic compositions changed when the samples were taken to laboratory measurements. High temperature analysis and on-line determination can be used to avoid changes in the sample, which occur during sample cooling and transportation (precipitation, oxidation, chemical reactions, etc.) As a conclusion, the research on development and testing of the instruments showed that CE could be used for troubleshooting purposes of processes (quality of the product and performing of machine condition).
Original languageEnglish
Title of host publication4th Pulp and Paper Chemical Analysis Seminar, September, Stockholm, Sweden
PublisherSkogs- och träforskningsinstitutet
Publication statusPublished - 2007
MoE publication typeA4 Article in a conference publication

Keywords

  • Analysis
  • pulp and paper

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