Emulsions are used in many everyday products, such as food and pharmaceuticals, and can be better stabilized by incorporating emulsifiers or additives, such as iron oxide nanoparticles (IONPs). Under the presence of an external magnet, IONPs can also aid in oil herding to remove oil from water. In this study, a coating, Kraft Lignin, is added to prevent aggregation and oxidation of IONPs. Specifically, lignin-Fe3O4 nanoparticles were synthesized using a co-precipitation approach. The fabricated nanoparticles were characterized using FT-IR spectroscopy, x-ray diffraction, thermogravimetric analysis, transmission electron microscopy, and dynamic light scattering and z-potential measurements. Large lignin-Fe3O4 clusters were observed in TEM; however, the DLS results revealed a Deff of ~ 170 nm. Once characterized, we studied the nanoparticles' effects in 10 mL castor-oil/water mixtures, at different ratios (1:9, 3:7, 5:5, 7:3, 9:1), analyzed at different concentrations. Droplet sizes at 0 minutes, 30 minutes, and 24 hours were measured using microscopy, and an increase in droplet size was found as the amount of oil increased. External magnetic fields were also investigated and ranged from 0 mT (control experiment) to 540 mT, and studies were also performed as a function of time. As the applied magnetic field increased, the lignin-Fe3O4 nanoparticles improved the demulsification and oil separation from the aqueous phase. Although the nanoparticles were initially dispersed in water, they appeared to migrate to the oil phase after the magnetic field was applied. The ability of lignin-magnetic nanoparticles to manipulate oil in oil/water mixtures was studied using alcohol (i.e., 1-pentanol) to facilitate the migration of the nanoparticles to the o/w interface. After multiple tests, it was found that there is a maximum nanoparticle concentration when increasing it no longer provides any beneficial results of herding the oil significantly (>5 mg/mL). Overall, this work demonstrates that lignin-Fe3O4 nanoparticles can stabilize and break oil/water emulsions comprised of castor oil. These nanoparticles can serve as additives in other types of oil separation from aqueous solutions. The oil separation using lignin biobased nanoparticles and FDA-approved magnetic nanoparticles could be instrumental in large-scale oil spills and recovery, helping the environment in a safe and low-cost way.

Lignin-Fe3O4 Nanoparticles form and destabilize pickering emulsions and serve as additives for oil herding and manipulation

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.