(58r) Large-Scale Separation Efficiency of Dispersed Oil Micro-Droplets from Aqueous Phase with Magnetic Nanoparticles

Introduction: Gravity separators are favored with regard to removing dispersed oil droplets from water, due to their low operating and maintenance cost. This conventional solution takes advantage of gravity or density differences in oil and water. The separation process usually takes 12-24 hours and oil-removal efficiency will reach 69-82%. With the elevated environmental concerns about the produced formation fluids, efficient and fast methods are required to process large volumes of water at water treatment facilities.

Theory: Application of magnetic nanoparticles (MNPs) in removing oil from oil-in-water emulsion is proved efficient at lab-scale. The term magnetophoresis (MAP) refers to the phenomenon of a magnetic particle moving through a viscous fluid medium in an external non-uniform magnetic field. An efficiently designed MAP method successfully removes 95-99.5% of oil colloids in less than one hour. MAP theory is favorably applied for particle separation, especially cell separation in biomedical and material sciences. MNPs exhibit superparamagnetic properties and respond to an external magnetic field easily until the field is removed. This allows the mechanical control of MNPs motion in a carrier fluid by magnetic field, which serves as the fundamental concept for a MNP-based separator design.

Methods: A comprehensive study of MAP involves nanoparticle synthesis, advanced magnetism, particle-laden flow dynamics, particle tracing, and analytical and numerical analyses. This study presents numerical modeling of magnetic nanoparticle motion in a magnetic fluid medium under an external magnetic field. Strong emphasis is given to the compilation of the available experimental data and matching the observed experimental results. A comprehensive semi-analytic diagnostic model is presented to understand the fundamental dynamic of the key design parameters involved, followed by a more complex, tuned numerical model.

Contributions: The contributions of this study are (1) to identify the feasibility of magnetic separation in oil removal, and (2) to optimize a magnetic separator design by investigating optimum MNP concentration, MNP diameter, and required external magnetic field strength, and (3) to quantify the optimum MNP separation efficiency when large-scale flowrates are applied.