Valorization of expired energydrinks by designed and integrated ionic liquid-based aqueous biphasic systems

Abstract

Expired energy drinks are rich in bioactive value-added compounds that can be recovered and reused in order to valorize food waste within a circular economy perspective. However, to accomplish such requirements, it is necessary to develop sustainable extraction and recovery processes, which must consist of decreasing the number of steps required or developing integrated strategies. In this work, novel aqueous biphasic systems (ABS) composed of ionic liquids (ILs) and a biocompatible polymer polypropylene glycol (400 g·mol-1, PPG 400) were studied for the simultaneous extraction and recovery of three value-added compounds, namely, caffeine, taurine, and niacin, from expired energy drinks. ILs were designed and synthesized in order to have similar anions to the target compounds, thus allowing enhanced selectivity and biological activity, while avoiding an extra step of separation of these high-value compounds from the IL-rich phase. To this end, cholinium-based ILs comprising the anions lactate, pyruvate, taurate, and nicotinate were synthesized, and their cytotoxicity and ecotoxicity credentials were evaluated. Overall, taurine and niacin are majorly enriched in the IL-rich phase, while caffeine preferentially migrates in the majority of the cases toward the PPG-rich phase. However, caffeine also partitions to the IL-rich phase in the ABS formed by cholinium pyruvate or cholinium nicotinate. The ABS formed by cholinium nicotinate and PPG 400 is the best system identified, allowing the almost complete recovery (recovery efficiencies > 82%) of all target compounds into the IL-rich phase in one step. Furthermore, cholinium nicotinate exhibits marginal cytotoxic potential and is harmless from an ecotoxicological point of view. This system is thus a promising platform to simultaneously extract, recover, and reuse value-added compounds from expired energy drinks without the need of removing the IL or recovering the target compounds from the IL-rich phase, thus contributing to a sustainable and circular food economy