Lignin nanoparticles as co-stabilizers and modifiers of nanocellulose-based Pickering emulsions and foams

Abstract

Nanocellulose is very hydrophilic, preventing interactions with the oil phase in Pickering emulsions. This limitation is herein addressed by incorporating lignin nanoparticles (LNPs) as co-stabilizers of nanocellulose-based Pickering emulsions. LNP addition decreases the oil droplet size and slows creaming at pH 5 and 8 and with increasing LNP content. Emulsification at pH 3 and LNP cationization lead to droplet flocculation and rapid creaming. LNP application for emulsification, prior or simultaneously with nanocellulose, favors stability given the improved interactions with the oil phase. The Pickering emulsions can be freeze–dried, enabling the recovery of a solid macroporous foam that can act as adsorbent for pharmaceutical pollutants. Overall, the properties of nanocellulose-based Pickering emulsions and foams can be tailored by LNP addition. This strategy offers a unique, green approach to stabilize biphasic systems using bio-based nanomaterials without tedious and costly modification procedures.

Preparation of Lignin-Based Nanoparticles with Excellent Acidic Tolerance as Stabilizer for Pickering Emulsion

“…As a kind of aromatic biopolymer, lignin has a hydrophilic hydroxyl group and hydrophobic benzene ring structure, and it has been employed in various applications such as emulsion stabilizers due to its amphiphilic property [ 18 , 19 ]. Currently, various lignin-based particles with different sizes, e.g., microparticles (1 μm~100 μm) [ 20 ], sub-microparticles (100 nm~1.0 μm) [ 21 ], and nanoparticles (1 nm~100 nm) [ 22 , 23 ], have been developed as effective stabilizers for Pickering emulsions. Compared to colloidally unstable and interpenetrating micro- and larger-sized lignin particles, the lignin nanoparticles (LNPs) display enhanced adsorption ability at the oil–water interface of the emulsions, which are beneficial to the formation of stable and homogeneous Pickering emulsions [ 24 ].…”