Optimization and Evaluation of Organic Acid Recovery from Kraft Black Liquor Using Liquid-Liquid Extraction

Abstract

− Liquid-liquid extraction (LLE) can be used for the recovery of acetic acid from black liquor prior to bioethanol fermentation. Recovery of value-added chemicals such as acetic-, formic-and lactic acid using LLE from Kraft black liquor was studied. Acetic acid and formic acid have been reported to be strong inhibitors in fermentation. The study elucidates the effect of three reaction parameters: pH (0.5~3.5), temperature (25~65 o C), and reaction time (24~48 min). Extraction performance using tri-n-octylphosphine oxide as the extractant was evaluated. The maximum acetic acid concentration achieved from hydrolyzates was 69.87% at 25°C, pH= 0.5, and 36 min. Factorial design was used to study the effects of pH, temperature, and reaction time on the maximum inhibitor extraction yield after LLE. The maximum potential extraction yield of acetic acid was 70.4% at 25.8°C, pH=0.6 and 37.2 min residence time.

Homogeneous Metal Salt Solutions for Biomass Upgrading and Other Select Organic Reactions

“…For example, at optimized conditions (35% methanol + saturated K 2 HPO 4 (pH 10.7)), 98% of the 1,3-propanediol was recovered . Response surface methodologies have proved effective for determining optimal extraction conditions. − For lactic acid, Aydoğan et al achieved a maximum partition coefficient and recovery when the lactic acid solutions were treated with 30% ethanol and 18% K 2 HPO 4 . Further studies in actual fermentation broths showed a recovery higher than 90% in an ethanol/methanol mixture and K 2 HPO 4 …”

Recovery and Enrichment of Organic Acids from Kraft Black Liquor by an Adsorption-Based Process

“…Moreover, compatibility of such separation processes with the overall kraft process is a key requirement since the remaining components of BL (water, inorganics, lignin) must be returned to the kraft process. Proposed separation processes to recover HA mixtures from BL ,− mostly involve BL pretreatment for lignin removal to clarify the BL and facilitate further processing. Acid precipitation and membrane filtration are the two main methods to separate lignin, ,, with adsorption also possible for removing lower concentrations of lignin .…”

“…In the alkaline conditions of BL, the organic acids are in the form of sodium salts. However, they must be recovered as acids to enable valorization, for which the addition of a strong inorganic acid (e.g., sulfuric acid) or ion exchange with a cationic resin is the typical process. , Subsequently, different combinations of methods such as distillation, crystallization, electrodialysis, liquid–liquid extraction, , esterification of organic acids followed with distillation, ion exclusion, and ion exchange have been investigated to separate the organic acids from inorganic salts in the clarified BL. However, all of the above processes have low efficiency and high capital cost, and the extraction-based processes often require the use of organic solvents with undesirable sustainability indices and elevated toxicity.…”