Production and purification of phytic acid from distillery wastewater via ion exchange

Abstract

Phytate (inositol hexakisphosphate) is the major form of organic phosphorus present in corn. Phytate is partially degraded during the corn ethanol fermentation process and it still represents over 40% of the phosphorus present in the main co-product generated – distiller’s grains. Phytate has a high market value and its extraction can help decrease phosphorus pollution from distiller’s grains use as animal feed. An ion exchange system has been developed for phytate extraction and purification using the ethanol co-products streams. The feedstock rich in phytate for this study is complex and presents different competing ions for the ion exchange system. The anion exchange resin used is selective for phytate, but is also able to adsorb sulfate, inorganic phosphate, and nitrate – all of which are as concentrated as phytate in the feedstock stream. This study evaluated some of the experimental conditions for better understanding the phytate extraction and purification system, and include the development of multi-component isotherms and multi-anion adsorption kinetics. The adsorption breakthrough for the four anions has also been evaluated on a packed-bed chromatographic column, on a similar design that would be used for larger scale approaches. Desorption from fully loaded resin, followed by a phytate precipitation step, provided salts with purities higher than 90%. This system can, thus, lead to a potential industrial application in order to enhance the profitability of ethanol plants, and simultaneously providing a solution for phosphorus pollution from distiller’s grains use.