Lignin-magnetite nanoparticles aiding in pickering emulsions and oil manipulation and their rheological properties

Date of Award

2021

Degree Name

M.S. in Chemical and Materials Engineering

Department

Department of Chemical and Materials Engineering

Advisor/Chair

Erick Vasquez

Abstract

Emulsions are used for many biological, pharmaceutical, and food purposes and require a non-toxic, eco-friendly emulsifier to keep them stabilized over time. Iron oxide nanoparticles (IONPs) have been thoroughly studied and used as an additive in emulsions to form Pickering emulsions. In this study, Kraft lignin, a type of biopolymer obtained from Kraft pulp, was used as a coating for the IONPs to prevent agglomeration and oxidation. Specifically, lignin@Fe3O4 nanoparticles were synthesized using a co-precipitation bottom-up approach and were characterized using multiple techniques, such as Fourier-Transform Infrared Spectroscopy (FT-IR), Thermogravimetric Analysis (TGA), Dynamic Light Scattering (DLS), and Vibrating-Sample Magnetometer (VSM). After confirming the formation of lignin@Fe3O4, these nanoparticles were used to prepare Pickering emulsions with castor oil/sudan red G dye and pure water. Five different oil/water ratios were tested (10/90, 30/70, 50/50, 70/30, and 90/10), along with three nanoparticle concentrations (0.1, 0.5, and 1.0 w/v%) and 5 magnetic fields (540, 370, 100, 5, and 0 mT). The emulsion stability without a magnetic field was determined by measuring droplet sizes using microscopy techniques as a function of time. The Pickering emulsions, stabilized by lignin@Fe3O4, can also undergo a demulsification process using external magnetic fields, successfully separating the oil and the aqueous phase. Also, this study shows that an aqueous lignin@Fe3O4 nanoparticle solution and 1-pentanol adsorb at the oil/water interface and can be used to herd spilled oil on water, exemplifying the adsorptive properties of IONPs. The successful Pickering emulsions then had their magnetorheological properties tested on a rheometer. Flow, amplitude, and frequency sweep tests were run at 0 mT and 60 mT and proved that applying a magnetic field can change the emulsions' rheological behavior, from liquid-like to solid-like, as nanoparticle concentration increased. Overall, this work highlights the superparamagnetic and adsorptive properties of lignin magnetite nanocomposites as additives that form and break Pickering emulsions, serve for oil herding, and possess a responsive magnetorheological behavior.

Keywords

Chemical Engineering, Chemistry, Materials Science, Nanoscience, Sustainability, Magnetic nanoparticles, pickering emulsions, magnetorheology, oil herding, lignin-magnetite, castor oil, oil removal

Rights Statement

Copyright © 2021, author.

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