Impact of the anions in the production of monolithic cellulose aerogels

Abstract

Academia and industry are developing ways to produce novel materials from renewable bio-based sources. Cellulose is the most abundant polysaccharide on Earth and it is known for its renewability, low economical and environmental footprint as well as chemical and thermal stability. We are developing strategies to improve the properties and gelation time of cellulose aerogel monoliths and sheets by adding sodium salts in the solution preparation phase. Cellulose solution was prepared by dissolution method using a mixture of NaOH, urea and water as solvent. The slow gelation of the solution hinders the creation of a stable monolith shape as the up-scaling of its production. The addition of salts can induce gelation of the solution. Sodium salts of chloride, sulphate and citrate have been employed. In the present study the impact of anions have been explored. The impact of anions in the cellulose solution behaviour are studied through rheology by controlling temperature and gelation time. The influence of parameters such as the concentrations, charge densities and anionic nature of the salts are analysed. The production of highly porous aerogels are accomplished by supercritical drying. The produced cellulose aerogels are characterized by nitrogen adsorption-desorption isotherm, BJH pore data analyses, density analyses, powder X-ray diffraction, FTIR and scanning electron microscopy. The physical properties are compared which indicated that the aerogels present a porous network structure similar to classic aerogels depending upon the anions added. The addition of salts reduces the gelation time and physically supports the creation of a stable monolith. Acknowledgement: This project has received funding from the European Union's Horizon 2020 research and innovation programme under Marie Skolodowska-Curie grant agreement ID: 956621. It is carried out in a partnership between German Aerospace Center and the industrial partner KEEY Aerogel, Habsheim, France.