Microcrystalline Cellulose from Aloe Plant Waste as a Platform for Green Materials: Preparation, Chemical Functionalization, and Application in 3D Printing

Aloe represents a valuable resource for the Mediterranean economy; the pharmaceutical and nutraceutical industries exploit the Aloe gel for several applications, but about 45 wt % of the Aloe plant, i.e., the leaf peel, is waste. This waste is usually disposed off in a landfill or used as a fertilizer. The possibility to give added value and a second life to the portions of Aloe Vera waste will help this growing market enter a circular economy perspective. In this work, waste collected from the local Sardinian cultivation of Aloe Vera was employed to prepare microcrystalline cellulose (MCC). Cellulose was purified from anthraquinones, lignin, and hemicellulose through hydrolytic procedures using eco-friendly solvents. Anthraquinone biocomponents, as well as lignin and hemicellulose, were quantified and intended for other valorization processes. At the same time, the cellulose fraction was further converted into MCC and characterized by NMR and infrared spectroscopy and X-ray analyses. TGA-IR and SEM microscopy analyses were performed to investigate the structural changes of MCC during the extraction and postfunctionalization processes. MCC derivatives were finally used as cross-linkers in the photopolymerization and light-induced 3D printing (VAT printing) of acrylic monomers and hydrogels.