(176am) Amphiphilic Hairy Cellulose Nanocrystals: A Sustainable Solution for Scale-Resistant Multiphase Flows

Nucleation and growth of sparingly soluble salts (i.e., scaling) has posed tremendous operational damages to industrial processes involving multiphase flows, such as enhanced oil recovery (EOR). During crude oil extraction/recovery, seawater is injected into oil reservoirs to facilitate the oil displacement through the wellbore which generates water-in-oil (W/O) emulsions. The calcium ion (Ca²⁺) abundance and carbon dioxide (CO₂) dissolution in alkaline seawater (pH ~ 8.1) may result in calcium carbonate (CaCO₃) scaling in the emulsions. In such multiphase flow processes, there is an urgent need for engineering materials that not only prevent scale formation but also simultaneously stabilize emulsions. Current antiscaling macromolecules and nanoparticles impose adverse environmental impacts and/or are limited to functioning only in single-phase aqueous media. In this study, we developed an innovative class of antiscaling cellulose-based nanoparticles that enable scale-resistant W/O Pickering emulsions. Plant-derived cellulose fibrils are rationally nanoengineered to amphiphilic hairy cellulose nanocrystals (AmHCNC), comprising a high density of dicarboxylate groups (COO^- ~ 3.1 mmol g^−1) that impart antiscaling properties to supersaturated aqueous droplets, as well as hydrophobic alkyl chains, enabling nanoparticle oil wettability. The unique chemical properties and hairy architecture of AmHCNC render it the first dual-functional antiscaling and emulsion stabilizing nanoparticle. To evaluate the AmHCNC functionalities, W/O Pickering emulsions, containing CaCO₃ scales, with uniform droplet sizes were generated via a flow focusing microfluidic device. AmHCNC stabilized W/O Pickering emulsions at a concentration of 1 wt.% for one week while inhibiting CaCO₃ scale formation up to 70% by mass compared with the synthetic surfactant Span 80. Mediated by electrostatic interactions between the anionic groups (COO^-) and Ca²⁺ (cation) in CaCO₃, the protruding dicarboxylate chains of AmHCNC at the water-oil interface partially arrest CaCO₃ crystallization at the least thermodynamically stable crystalline polymorph, vaterite, at the ambient condition. This study presents a novel biopolymer-based solution to address the persistent challenge of scaling in multiphase media, offering promising prospects for the development of sustainable, scale-resistant multiphase flows across various industrial sectors.