Valorization of Spent Coffee by Caffeine Extraction Using Aqueous Solutions of Cholinium-Based Ionic Liquids

Abstract

Spent coffee grounds (SCGs) are a waste product with no relevant commercial value. However, SCGs are rich in extractable compounds with biological activity. To add value to this coffee byproduct, water and aqueous solutions of cholinium-based ionic liquids (ILs) were studied to extract caffeine from SCGs. In general, all IL aqueous solutions lead to higher extraction efficiencies of caffeine than pure water, with aqueous solutions of cholinium bicarbonate being the most efficient. A factorial planning was applied to optimize operational conditions. Aqueous solutions of cholinium bicarbonate, at a temperature of 80 °C for 30 min of extraction, a biomass–solvent weight ratio of 0.05 and at an IL concentration of 1.5 M, made it possible to extract 3.29 wt% of caffeine (against 1.50 wt% obtained at the best conditions obtained with pure water). Furthermore, to improve the sustainability of the process, the same IL aqueous solution was consecutively applied to extract caffeine from six samples of fresh biomass, where an increase in the extraction yield from 3.29 to 13.10 wt% was achieved. Finally, the cholinium bicarbonate was converted to cholinium chloride by titration with hydrochloric acid envisioning the direct application of the IL-caffeine extract in food, cosmetic and nutraceutical products. The results obtained prove that aqueous solutions of cholinium-based ILs are improved solvents for the extraction of caffeine from SCGs, paving the way for their use in the valorization of other waste rich in high-value compounds.

Application of the Solute–Solvent Intermolecular Interactions as Indicator of Caffeine Solubility in Aqueous Binary Aprotic and Proton Acceptor Solvents: Measurements and Quantum Chemistry Computations

“…This is due to their beneficial properties including excellent solubilizing potential, environmental friendliness and relatively low cost of preparation. Additionally, the behavior of caffeine in these designed solvents was studied [ 72 , 73 , 74 , 75 , 76 ]. Particularly interesting are the results of caffeine extraction from spent coffee grounds using cholinium-based ionic liquids [ 72 ].…”

“…Additionally, the behavior of caffeine in these designed solvents was studied [ 72 , 73 , 74 , 75 , 76 ]. Particularly interesting are the results of caffeine extraction from spent coffee grounds using cholinium-based ionic liquids [ 72 ]. Our research team has previously published the results of theophylline and theobromine solubilized in natural deep eutectic solvents utilizing choline chloride [ 1 , 2 ] and similar results regarding caffeine will follow.…”

Quantification of Caffeine Interactions in Choline Chloride Natural Deep Eutectic Solvents: Solubility Measurements and COSMO-RS-DARE Interpretation

“…In recent years, due to the increasing demand for alternative solvents, the solubility of caffeine in ionic liquids and NADES also became a subject of interest. These studies were focused mainly on extraction of caffeine from natural sources and involved such media as cholinium-based ionic liquids [ 78 ], imidazolium-based ionic liquids [ 79 ], amino acid-based ionic liquids [ 80 ], systems containing sorbitol [ 81 ] and DES [ 82 ].…”

Assessment of Ultrasound-Assisted Extraction of Caffeine and its Bioactivity

“…Non-traditional methods have been developed to extract caffeine with less negative environmental impact, such as ionic liquid-assisted extraction (Zhang et al, 2021), and microwave-assisted extraction (Lopes et al, 2020). These methods provide a great caffeine recovery with less negative environmental impact by reducing solvent usage, yet they require expensive materials and a substantial energy supply (Ferreira et al, 2021). The ultrasound extraction method is one of the modern "green and innovative" methods (Hasan et al, 2018) (Mohammed et al, 2016) that are considered an efficient alternative to conventional solid-liquid extraction, methods as it is relatively cost-effective, simple, versatile, and it is possible to scale up (Chemat et al, 2017).…”