Extractive Adsorption of Lactic Acid from Fermentation Broth on a Novel Ion Exchange Resin Impregnated by the [Bmim]PF6 Ionic Liquid

In this study, extraction by the green solvent of an ionic liquid (IL) combing adsorption technology was proposed to investigate the sustainable separation of biolactic acid from the fermentation broth for the first time. First, a new resin IL-335 was prepared by impregnating a weak-base anion exchange resin 335 in an IL of [Bmim]PF6. Its characteristics were described by SEM, EDS energy spectrum, FTIR, and physical adsorption analysis. The analysis of FTIR and quantum chemical calculations by density functional theory showed that two hydrogen bonds exist between lactic acid (LA) and [Bmim]PF6. The static adsorption could be described by the Langmuir and Freundlich isotherm models and the pseudo-second-order model. The maximum adsorption capacity of the IL-335 resin for LA from a synthetic solution was 605 mg/g, which was 52.97% higher than that of the untreated 335 resin. The extraction and adsorption contributed to 34.55 and 65.45% of the capacity, respectively. The maximum dynamic adsorption capacity of LA was 489 mg/g in column chromatography, and the dynamic adsorption behavior could be described by the Thomas and Yoon-Nelson breakthrough models. Furthermore, the IL-335 resin exhibited excellent selectivity and a sustainable separation efficiency for LA after six cycles of extractive chromatography. This study combined the dual role of extraction and adsorption to develop the extractive adsorption technique in the separation of biolactic acid for the first time, which highlights a potential separation approach to meet the challenges of biobased LA industrialization.