Technologies for the isolation of lignin from pulping process streams are reviewed in this article. Based on published data, the WestVaco process, the LignoBoost process, the LigoForce SystemTM and the SLRP process are reviewed and discussed for the isolation of lignin from Kraft black liquor. The three new processes that have now joined the WestVaco process are compared from the perspective of product quality. Further, isolation processes of lignosulfonates from spent sulfite liquor are reviewed. The limitation for this review is that data are only available from lab scale and pilot scale experiments and not from industrial processes. Key output of this paper is a technology summary of the state of the art processes for technical lignins, showing the pros and cons of each process.

The majority of commodity plastics is made from petroleum-based chemicals. Lactic acid serves as a monomer for the production of the biodegradable polymer polylactic acid (PLA). This paper provides a review on the state of the art production and isolation process for lactic acid. Problems in production and isolation have been identified, the relevant results in optimized production are presented in the first part of the paper. In the second part, a decision matrix is used as a guideline for the discussion on the state of research in the isolation and purification of lactic acid. Mechanical unit operations, mass transfer unit operations, reactive separation techniques, and process combinations are reported in the literature. At the end, an economic evaluation of isolation processes such as conventional precipitation, reactive membrane separation, and reactive distillation are presented.

The present work develops the basics for the isolation of lactic acid, acetic acid and formic acid from a single as well as a mixed feed stream, as is present, for example, in fermentation broth for lactic acid production. Modelling of the phase equilibria data is performed using the law of mass action and shows that the acids are extracted according to their pka value, where formic acid is preferably extracted in comparison to lactic and acetic acid. Back-extraction was performed by 1 M NaHCO3 solution and shows the same tendency regarding the pka value. Based on lactic acid, the solvent phase composition, consisting of tri-n-octylamine/1-octanol/n-undecane, was optimized in terms of the distribution coefficient. The data clearly indicate that, compared to physical extraction, mass transfer can be massively enhanced by reactive extraction. With increasing tri-n-octylamine and 1-octanol concentration, the equilibrium constant increases. However, even when mass transfer increases, tri-n-octylamine concentrations above 40 wt%, lead to third phase formation, which needs to be prevented for technical application. The presented data are the basis for the transfer to liquid membrane permeation, which enables the handling of emulsion tending systems.

Kraft lignin can be extracted from black liquor generated during wood digestion. At present, water soluble kraft lignin is prepared chemically. Here, a method for the preparation of a purified form of CO2‐precipitated softwood kraft lignin, which forms a stable aqueous solution at a pH value of 8.9 is described. The lignin samples are characterized by thermogravimetric analysis, IR spectroscopy, nuclear magnetic resonance spectroscopy, and gel permeation chromatography. The comparison of water‐washed lignin with reference samples of unwashed‐ and acid‐washed lignin shows that the water‐washed lignin has a higher molecular weight compared to the reference samples, while the content of hydroxyl and methoxyl groups is similar. Solubility studies show that drying of washed lignin has a significant effect on its dissolution in water. Charge titration and dynamic light scattering experiments show that water‐washed lignin forms a stable colloid in aqueous solution.

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