(170c) Fabrication of Hydrogel/Aerogel from Recycled Biomass

Hydrogel is a soft matter of a three-dimensional polymer network swollen by a large amount of water. Dependent on polymers, fabrication method, and functionalization, a hydrogel can have different properties such as stretchability, compressibility, water retention, pH sensitivity, and conductivity. Hydrogels have been widely utilized in the fields such as biomaterials, agriculture, and water purification. Aerogel is an ultralight material derived from a gel (in many cases, a hydrogel), where the liquid component in the gel has been replaced with a gas. In general, aerogels have low density, high porosity, and many unique properties in the meantime. Current hydrogels and aerogels are mainly fabricated from synthesized polymers or cross-linked by additional chemical agents. With the increasing demand for green material and sustainable processes, more attention has been drawn to developing hydrogels and aerogels from natural and renewable materials.

Cellulose is an abundant natural polymer on earth and has been used for fabricating hydrogels and aerogels. One of the cellulose-based hydrogel/aerogel fabrication approaches is the dissolution-regeneration process. Diverse solvent systems such as LiCl/dimethylacetamide (DMAc), N-methylmorpholine-N-oxide (NMMO), ionic liquids (ILs), and alkali/urea (or thiourea) aqueous systems have been used to fabricate cellulose-based hydrogels/aerogels in previous studies. Compared with the above solvents, inorganic salt solvents have lower vapor toxicity and relatively lower price. In addition, they are easy to use and recycle.

Herein, we report a facile route to fabricate cellulose hydrogel and aerogel directly from recycled biomass using zinc chloride salt hydrate as a cellulose solvent. Zinc chloride is a well-known cellulose swelling and dissolving agent. The cellulose regeneration process is simple, rapid, and under mild conditions to form a hydrogel. The aerogel obtained after the lyophilization of the hydrogel showed high stiffness and lightweight. The fabricated hydrogel and aerogel were characterized using dynamic mechanical analysis (DMA), scanning electron microscope (SEM), differential scanning calorimetry (DSC), and Fourier-transform infrared spectroscopy (FTIR). This study could pave a new way to valorize the recycled biomass.