Cellulose as a Natural Emulsifier: From Nanocelluloses to Macromolecules

During the last decade, cellulose structural features have been revisited, with particular focus on its structural anisotropy (amphiphilicity) and interactions determining its recalcitrance to dissolution. Evidences for cellulose amphiphilicity are patent, for instance, in its capacity to adsorb at oil–water interfaces, thus being capable of stabilizing emulsions. This behavior is observable in all its forms, from cellulose nanoparticles to macromolecules. This chapter is divided into two main parts; first, the fundamentals of emulsion formation and stabilization will be introduced, particularly focusing on the role of natural emulsifiers. Secondly, the emerging role of cellulose as a natural emulsifier, where the ability of cellulose to form and stabilize emulsions is revisited, from cellulose nanoparticles (Pickering-like effect) to macromolecules (i.e., cellulose derivatives and native molecular cellulose).

Properties Of Cellulose Nanofibers Extracted From Eucalyptus And Their Emulsifying Role In The Oil-In-Water Pickering Emulsions

In this work, nanocellulose particles were obtained from eucalyptus fibers by high-pressure homogenization (CNF) and by high-intensity ultrasound (SCNF). The nanocellulose was applied as a solid emulsifier for soybean oil in water (O/W) emulsions. The adding of 0.25 - 1 wt.% of both CNF and SCNF produced stable O/W emulsions without conventional surfactants. SCNF emulsions showed the highest stability and displayed the narrowest size distribution. Zeta potential values (-40 to -70 mV) indicated an electrical barrier to the droplet coalescence. The rheological behavior of O/W emulsions stabilized with CNF and SCNF was described by the Herschel-Buckley model. O/W emulsions produced with nanocellulose particles behave as shear thinning fluid, and their behavior index ranged from 0.33 to 0.68. Both CNF and SCNF emulsions displayed maximum yield stress at a particle concentration of 0.5wt.% and 0.75wt.%, respectively. Besides, the prepared O/W emulsions using 0.5 to 1.00 wt.% CNF or SCNF did not showed phase separation until 30 days of rest. The data point out to the feasibility of using nanocellulose as a natural emulsifier, which can replace conventional surfactants.

Effect of Nanocellulose on Water-Oil Interfacial Tension

Interfacial tension is an important parameter in enhanced oil recovery (EOR). The interaction between water and oil phase is a determinant factor of the interfacial tension. The interfacial tension changes if another component is added to the water-oil system. This study investigates the effect of adding nanocellulose to the water-oil system. To determine the molecular interactions that occur, a molecular dynamics simulation was carried out using the GROMACS-2018 software. The simulation shows that addition of nanocellulose slightly decreases the water-oil interface tension. Further, based on the density profile, nanocellulose may act as an emulsifier due to its geometric position in the water-oil interface. This is similar to asphaltene, which is a natural emulsifier in crude oil. The nanocellulose performs better in the presence of 1% NaCl as compared to pure water.