Lignin Nanoparticles as Highly Efficient, Recyclable Emulsifiers for Enhanced Oil Recovery
Kai Gao is a PhD student in the Department of Materials Science and Technology of Polymers. Promotors are prof.dr. G.J. Vancso from the Faculty of Science & Technology and prof. X. Sui from the Donghua University, China.
Lignin, a renewable and plant-derived biopolymer, has attracted increasing interest for its high-value applications in sustainable technologies. This Thesis focuses on the synthesis, characterization, and application of lignin nanoparticles (LNPs) as eco-friendly emulsifiers for enhanced oil recovery (EOR). LNPs were prepared via a simple and cost-effective dissolution–regeneration method using three types of lignin (corn, alkali, and kraft lignin). Their molecular structures were analyzed by 2D-HSQC and 31P NMR, revealing variations in aromatic units and hydroxyl group content.
LNPs demonstrated the ability to stabilize oil–water Pickering emulsions at low concentrations. Importantly, the emulsions could be demulsified under alkaline conditions (pH > 11), enabling efficient oil–water separation and nanoparticle reuse. Comparative emulsification studies with different oil types and LNP sources revealed that corn-derived LNPs exhibited superior emulsifying performance, likely due to a higher content of carboxylic acid groups. Additionally, combining LNPs with surfactants such as lignosulfonate (LS) and sodium dodecyl sulfate (SDS) further enhanced emulsion stability.
The adsorption behavior of LNPs on mineral-mimicking surfaces (silica and alumina) was investigated under varying salt conditions. Results showed stronger adsorption on alumina, especially in the presence of divalent ions (Ca²⁺), due to electrostatic interactions. Atomic Force Microscopy (AFM) provides insights into the spatial distribution of the adsorbed LNPs, indicating the adsorption is heterogeneous, with particles forming aggregates rather than a uniform layer.
Overall, this work highlights the potential of LNPs as recyclable, sustainable alternatives to conventional chemical emulsifiers in EOR, while also identifying current challenges and future directions for industrial implementation.
