Submitted to: RSC Advances
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/22/2020
Publication Date: 10/28/2020
Citation: Jordan, J.H., Easson, M.W., Condon, B.D. 2020. Cellulose hydrolysis using ionic liquids and inorganic acids under dilute conditions: morphological comparison of nanocellulose. RSC Advances. 10(65):39413-39424. https://doi.org/10.1039/d0ra05976e.
Interpretive Summary: The production of cellulose nanocrystals (CNCs) from cellulose fibers typically involves concentrated acids and produces large amounts of waste. As such, there has been considerable investigation into the use of alternative preparative methods for extraction of CNCs. One such method involves the use of ionic liquids, essentially a salt that is liquid at low temperature (<100 °C); however ionic liquids are themselves costly, and although typically they can be recovered, they can present their own challenges in dealing with hazardous waste. Herein, a method is reported to extract CNCs using a combination of either strong mineral acids and ionic liquids under dilute conditions, thus, significantly reducing the amount of acid waste that is produced and reducing the amount of ionic liquid required. The prepared CNCs are comparable to those produced under conventional conditions.
Technical Abstract: The preparation of cellulose nanocrystals (CNCs) from cellulose extracted from cotton gin motes (CGM) using an ionic liquid (1-butyl-3-methylimidazoliumm chloride, [BMIm]Cl) under dilute conditions is reported. The tandem two-step process involves minimal swelling of cellulose followed by the addition of either phosphoric (H3PO4), hydrochloric (HCl), or sulfuric (H2SO4) acid to initiate hydrolysis of the cellulose. Obtained nanocrystals had similar physical properties (e.g. crystallinity) to the counterparts prepared under conventional conditions and exhibited superior thermal properties. Additionally, the obtained CNCs had low surface functionalization, yet were colloidally stable for >90 days, which is a desirable trait for post-functionalization of CNCs. This represents a general strategy utilizing dilute ionic liquids in the preparation of nanocellulose under mildly acidic conditions.