Adsorption and Selective Recovery of Citric Acid with Poly(4-vinylpyridine).

Citric acid (CA) is an important organic acid that is produced on a large scale by fermentation. Current methods to recover CA from the fermentation broth require large amounts of chemicals and produce considerable amounts of waste, while not all CA can be recovered. The use of adsorbents can increase the degree of product recovery and reduce chemical consumption and waste generation. In this work, poly(4-vinylpyridine) (PVP) is evaluated as an adsorbent for CA recovery. It has a high adsorption capacity (>30 wt %) at low pH and a high selectivity for CA at moderate pH in the presence of sulfate anions, two conditions that are frequently encountered during CA recovery. PVP could be efficiently regenerated after adsorption using simple alcohols like methanol and ethanol. Considering selectivity and regeneration, PVP distinctly outperforms more common adsorbents for organic acids, including commercial strongly and weakly basic anion exchangers. The desirable adsorptive features of PVP for CA can be attributed to the low basicity of the pyridine group.