Hydrophilic/Oleophobic Magnetic Micrometer-Sized Particles for Separation of Water-in-Shale Oil Emulsions

Abstract

In comparison to conventional oil reservoir resources, shale oil production fluids exhibit strong emulsification properties, rendering conventional demulsification methods costly and less effective for efficient separation. To overcome these limitations, this study introduces a novel surface modification strategy utilizing low-cost, recyclable hydrophilic/oleophobic magnetic micrometer-sized Fe₃O₄ particles (M-MMPs) synthesized via a hydrothermal reaction. The surface chemical composition and wettability of the M-MMPs were characterized. The demulsification efficiency of the M-MMPs was evaluated, and the effects of the temperature, dosage, and number of recycling cycles on their demulsification efficiency were investigated. Finally, the demulsification mechanisms of the M-MMPs were discussed. For emulsions prepared under high shear rates, the demulsification efficiency of the M-MMPs was 38% higher than that of unmodified Fe₃O₄ particles (MMPs). The temperature exhibited a minimal impact on the demulsification efficiency of the M-MMPs, which sustained an efficiency of 60% even at 40 °C. The demulsification efficiency reached its peak when the M-MMP dosage was increased to 25 g/L. Notably, the M-MMPs demonstrated consistent demulsification efficiency over 10 recycling cycles without washing. Microscopic observation of the dynamic collision and capture of water droplets by the M-MMPs within the water-in-mineral oil emulsion revealed the demulsification mechanism of the M-MMPs. The hydrophilic surface effectively facilitates water droplet coalescence during collisions and capture. This demulsification mechanism suggests that the synergistic combination of a turbulent flow field and a magnetic field offers a promising approach for enhancing demulsification.