(44a) Pilot-Scale Adsorption Study for the Separation of Acetic, Butyric, and Lactic Acids

Organic acids, particularly short-chain carboxylic acids (e.g., acetic, lactic, and butyric), are produced through both chemical and biological processes. These acids serve as essential precursors in the production of various industrial products, including pharmaceuticals, cosmetics, textiles, polymers, and biofuels^1-3. Despite their broad applications, recovering organic acids from anaerobic fermentation process presents significant challenges due to their high solubility and relatively low concentrations⁴. Consequently, separation processes often become the primary bottleneck, typically accounting for 60–80% of total production costs⁵. Compared to traditional separation techniques, adsorption offers advantages such as simplicity of operation and selective separation from multi-component mixtures. Previous studies by Wu et al. ⁶, Hamid et al. ⁷, and Hamid et al. ⁸ have explored the application of adsorption for separating acetic, lactic, and butyric acids on a bench-scale setup. However, bridging the gap between laboratory experiments and industrial-scale processes requires an upscaling study to understand adsorption kinetics and selective removal. Therefore, this work proposes a pilot-scale experimental study to evaluate different operation conditions for three organic acids commonly found in fermentation broths—acetic acid, butyric acid, and lactic acid. The experiments were conducted using an anion exchange resin (IRN-78) as the adsorbent to separate single, binary, and ternary acid solutions at equimolar concentrations (200 mmol/L total), pH 6.0, and 25 °C. Experimental results indicated a breakthrough around 25 minutes for all organic acids in both single and multi-component solutions. Moreover, in the ternary mixture, sequential adsorption peaks were observed: lactic acid reached its maximum first (~27 min), followed by slight desorption; acetic acid peaked around 30 minutes; and finally, butyric acid around 75 minutes, consistent with the bench-scale breakthrough results reported by Hamid et al.⁸ for the same mixture. Additionally, the experimental data were used to validate the industrial applicability of three isothermal models: Langmuir, Freundlich, and Generalized Brunauer–Emmett–Teller (gBET). These results demonstrate that adsorption-based separation is a scalable technology for recovering carboxylic acids from aqueous solutions under fermentation conditions and offer valuable insight into the use of emerging isotherm models (e.g., gBET) for future industrial applications.

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