Pickering emulsions stabilized by nanocelluloses have been utilized within food, cosmetic, and pharmaceutical industries owing to their prolonged stability. However, high hydrophilicity and large dimension of cellulose nanofibrils (CNF) obtained through mechanical disintegration limit their adsorption at the oil/water interface. Herein, aldehyde-modified TEMPO-oxidized CNF (ACNF) with different oxidation degrees is prepared to improve Pickering emulsion stability, broadening its application in asphalt recovery. A battery of characterization methods (TEM, turbidity, contact angle, etc.) demonstrate the installation of aldehyde groups on the ACNF and change of the properties. The aldehyde groups improve hydrophobicity of ACNF while maintaining sufficient carboxyl groups to retain electrostatic repulsion. The fiber length of ACNF decreases with increasing aldylation degree, influencing the amount of ACNF absorbed at the droplet surface. Pickering emulsion stabilized by ACNF-0.12 show optimal performances. The obtained ACNF effectively stabilizes high oil content and different oil types with long-term stability. Flowable Pickering emulsions containing asphalt are obtained. This study offers comprehensive investigation on the influence of aldehyde-modified ACNF on Pickering emulsion preparation, aiming at developing new approaches for various applications.
Read full abstract