Drying and redispersion of plant cellulose nanofibers for industrial applications: a review

The broad range of applications of cellulose (CNFs) nanofibers derived from plant sources has promoted different strategies for their production and commercialization. Nevertheless, issues concerning its transportation have prompted different projects to achieve a redispersible and dehydrated product in order to allow a cost-effective and safe transport and processing of this material. In this work, different strategies to avoid hornification such as oven drying, freeze-drying, spray-drying and supercritical drying were reviewed in terms of the nanostructural properties and redispersion capability of the obtained product, analyzing the existent literature involving chemical modification of cellulose or additives. Oven drying was reported to have the highest agglomeration rate during dehydration and some of the redispersible products can be used in food and pharmaceutical products, while the structure of freeze-dried CNFs evidenced several morphologies depending on CNF concentration and the presence of charges or steric hindrances. Spray-drying and supercritical drying were the only methods that could not fulfil the aimed industrial requirements due to its agglomeration and cost-efficiency respectively. When considering strategies to keep nanostructural properties upon dehydration it is important to account for the final application of CNFs as some additives or chemical modifications are targeted to specific applications. Further research is still required to clarify if spray drying and supercritical drying are suitable for this nanomaterial, as different additives and drying parameters must be considered to adapt these techniques to industrial requirements