Response surface methodology for optimization of solvent extraction to recovery of acetic acid from black liquor derived from Typha latifolia pulping process

Abstract

Most modern commodity chemicals are synthesized from fossil resources. Organic acids are attractive targets in process development for the emerging renewable resources based biorefinery industry. Liquid-liquid extraction (LLE) is a common separation method for the recovery of a solute from a solution and can be applied to the recovery of acetic acid from the black liquor of Typha latifolia pulp prior to the bioethanol fermentation process. LLE of acetic acid was studied using alkanes containing 37% (w/w) concentrations of trioctylphosphine oxide. The extraction yield has also been evaluated with a four-level factorial design. Four independent variables, pH (1–3), temperature (25–65°C), residence time (24–48min), and concentrated hydrolyzates (1–10 times), were screened. The results showed that a lower pH and temperature gave the highest yield for the extraction of the organic acid. The yield also increased with less concentrated hydrolyzates. However, the residence time did not affect the yield. The maximum extraction yield of acetic acid achieved 71.7% at pH 1.02, 31.4°C, 46.8min, and 1.07 times. And the maximum extraction yield of formic acid and lactic acid was 75.1% (obtained at pH 1.46, 25.0°C, 44.5min, and 1.04 times) and 65.0% (obtained at pH 1.71, 35.9°C, 44.6min, and 1.11 times), respectively. It appears that the stabilities of the extracted acids are highly affected by the initial feed concentration of the organic acid.