Because of the capability of swelling and dissolving cellulose, inorganic molten salt hydrate (IMSH), such as lithium bromide trihydrate (LBTH, ~61 wt% aqueous solution of LiBr), has drawn increasing attention and has been successfully used in biomass processing and conversion. This presentation reports our recent studies on the fabrication of cellulose nanomaterials (nanocrystals and aerogels) from cellulose and/or lignocellulose via swelling/dissolution and regeneration in the LBTH. The dissolution of cellulose in LBTH is affected by LiBr concentration, temperature, pH, and cellulose properties (consistency, particle size, and degree of polymerization). It is the ion-dipole coordination between hydrated Li+ and cellulose hydroxyl that disrupts the intermolecular H-bond of cellulose and results in the dissolution of cellulose in the LBTH. The regeneration of the dissolved cellulose in the LBTH takes place in two independent steps, the cooling-induced gelation in which dissolved cellulose chains are crosslinked into a soft matter by Li+ cations through coordination with cellulose hydroxyl groups followed by the washing-triggered regeneration (precipitation) of the dissolved cellulose into a porous network when the soft matter is washed with water (non-solvent of cellulose) to recover LiBr. The cellulose polymorph was transformed from I to II during the processing. The fabricated aerogels were used in the metal and formaldehyde removal from water and indoor air and the energy harvesting by triboelectric nanogenerator (TENG), respectively.

Fabrication of nanocellulosic materials from cellulose and lignocellulose using molten salt hydrate and their environmental and energy applications