Recovery of Acetic Acid from the Prehydrolysis Liquor of Kraft Based Dissolving Pulp Production Process: Sodium Hydroxide Back Extraction from the Trioctylamine/Octanol System

Abstract

Acetic acid is an important potential product from the prehydrolysis liquor (PHL) of the kraft based dissolving pulp production process. This study focuses on the recovery of acetic acid from an industrial PHL from an Eastern Canadian Pulp mill that contains about 1% acetic acid. Reactive extraction with tri-n-octylamine (TOA) using octanol as a diluent was investigated as the potential process. Subsequently, the complexed acetic acid in the organic phase (TOA–octanol) was back extracted using a sodium hydroxide solution, while the solvent (TOA–octanol) was regenerated. The recovered acetic acid concentration was increased with increasing organic to aqueous phase ratio but at the expense of decreased extraction efficiency. At the organic to aqueous phase ratio of 40 and the NaOH to acetic acid (HAc) mole ratio of 1, the acetic acid concentration reached to 15.0, 9.8, and 10.3% for MAA (1% model acetic acid), PHL (prehydrolysis liquor), and TPHL (treated prehydrolysis liquor), respectively. It was concluded that the reactive extraction using TOA–octanol, followed by sodium hydroxide back extraction, is an efficient process in recovering and concentrating acetic acid from PHL.