Recycled ionic liquid<i> vs</i> . deep eutectic solvent in cellulose nanocrystals production: Characterization, techno-economic analysis, and life cycle assessment
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Date
2024
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Abstract
Three scenarios involving aqueous mixtures of neoteric solvents have been evaluated as solvents and catalysts for the cellulose hydrolysis reaction to obtain CNC in high yields (>70%). The scenarios considered were: scenario 1 (S1) involves a recyclable ionic liquid dilution of [Hmim][(HSO4)(H2SO4)]/H2O (64 wt% IL); scenario 2 (S2) another recyclable dilution of [Hmim][(HSO4)(H2SO4)]//H2O (80 wt% IL) and scenario 3 (S3) S3 ) a non-recyclable ternary deep eutectic solvent (60 wt% DES: choline chloride: oxalic acid/30 wt% PA/10 wt% water). Experimental analysis, techno-economic, and life cycle analysis (LCA) indicate that S1 emerges as a suitable scenario among the three analyzed. S1 demonstrated the highest competitiveness, with a lower raw material cost per gram of CNC produced (US$0.81/g) and lower environmental contributions concerning climate change and fossil fuel depletion, accounting mainly for its recyclability. Therefore, the recyclable dilution of 64 wt% IL used in S1 appears to be the most viable option for sustainable and environmentally conscious CNC production. Besides, the physicochemical properties of the CNC were revealed: aspect ratio range 7-8, high dispersion stability related to zeta potential >-40 mV, good crystallinity range 50-80%, and thermal stability with Tonset> 300 degrees C. These results guided towards a scenario with crucial advantages: a diluted IL that retains its acidity after reuse cycles by a facile recovery process, maintaining high CNC production performance and providing low environmental impacts.
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Ionic liquids, Deep eutectic solvents, Nanocellulose, Life cycle assessment