Purification process for recovering hydroxy acids from soda black liquor

Sanna Hellstén, Jussi Lahti, Jari Heinonen, Mari Kallioinen, Mika Mänttäri, Tuomo Sainio*

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

36 Citations (Scopus)


Black liquor, a side product of chemical pulping, contains hydroxy acids that have many potential applications, e.g., as polymer precursors. Currently there are no feasible separation processes available for recovery of hydroxy acids from such solutions. Neutralization is usually though to be a necessary pre-treatment, but it adds into chemical consumption and may impede the integration of the recovery process to a pulp mill. In this work, an experimental investigation of a new process concept for the recovery and purification of hydroxy acids from soda black liquor without neutralization is presented. The process consists of ultrafiltration, size-exclusion chromatography, ion-exchange, adsorption, and evaporation. Mixtures of hydroxy acids in high purity were produced from black liquor of soda pulping using the process. A reduction of 99% in lignin content of the organic acid fraction was achieved. In the chromatographic separation step, the recovery of sodium hydroxide was almost 100%. The average purities of hydroxy acids isolated from softwood and hardwood black liquors were 81% and 63% on mass basis, respectively.

Original languageEnglish
Pages (from-to)2765-2774
Number of pages10
JournalChemical Engineering Research and Design
Issue number12
Publication statusPublished - Dec 2013
MoE publication typeA1 Journal article-refereed


  • Black liquor
  • Chromatography
  • Hydroxy acids
  • Membrane filtration


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