Date of Award


Level of Access Assigned by Author

Campus-Only Dissertation

Degree Name

Doctor of Philosophy (PhD)


Chemical Engineering


G. Peter van Walsum

Second Committee Member

Adriaan R.P van Heiningen

Third Committee Member

M. Clayton Wheeler


Carboxylic acids are commonly generated in biorefinery operations such as fermentation or aqueous extraction of hemicellulose feedstocks. In most cases, organic acids are generated as dilute components in aqueous streams. If they can be recovered from solution inexpensively they may find value as pure chemical products or as starting materials for a wide variety of organic products, including biofuels.

Liquid-liquid extraction is a separation method applied to recover mixed carboxylic acids from a fermented wood extract. These acids included: acetic, propionic, butyric, valeric, caproic and heptanoic acids. An organic solution, such as trialkylphosphine oxide (CYANEX 923, a mixture of four trialkylphosphine oxides), was mixed with fermented wood extract to extract these acids. Although the extraction was highly effective, however it was shown that distillation was not able to recover these acids from the extraction solvent.

In this study, after liquid-liquid extraction of the acids from the aqueous phase, the mixed acids are recovered from the organic phase by a back extraction with sodium hydroxide. The mixture is agitated and centrifuged to separate the organic and aqueous phases. Results present the extraction and recovery efficiencies of this method of recovery organic acids.

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