Extensional Magnetorheology as a Tool for Optimizing the Formulation of Ferrofluids in Oil-Spill Clean-Up Processes

José Hermenegildo García-Ortiz,Francisco José Galindo-Rosales

doi:10.3390/pr8050597

José Hermenegildo García-Ortiz, Francisco José Galindo-Rosales

Open Access

https://doi.org/10.3390/pr8050597

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Journal: Processes	Publication Date: May 17, 2020
Citations: 5	License type: CC BY 4.0

Affiliation: University of Porto

Abstract

In this study, we propose a new way of optimising the formulation of ferrofluids for oil-spill clean-up processes, based on the rheological behaviour under extensional flow and magnetic fields. Different commercial ferrofluids (FFs), consisting of a set of six ferrofluids with different magnetic saturation and particle concentration, were characterised in a Capillary Break-Up Extensional Rheometer (CaBER) equipped with two magnetorheological cells that allow imposing a homogeneous and tunable magnetic field either parallel or perpendicular to the flow direction. The filament thinning process with different intensities and orientation of the magnetic field with respect to the flow direction was analysed, and the results showed that the perpendicular configuration did not have a significant effect on the behaviour of the ferrofluids, as in shear magnetorheometry. However, the parallel configuration allowed to determine that the formulation of ferrofluids for oil-spill cleaning processes should consist of a 4% vol concentration of magnetic nanoparticles with a magnetic saturation of M s > 20 mT.

Highlights

As long as our model of society keeps consuming products derived from crude oil, oil spills and discharges will be unavoidable
When the mixture is placed in an oil-recovery vessel containing an array of arranged permanent magnets, the magnetic fluid in the reservoir is attracted towards the lateral surface of the magnetic rods undergoing an extensional flow, as shown in Figure 1; and the ferrofluid climbs to the top of the array, above reservoir level, forming beaded spheres around the magnets’ ends
The experiments were performed by using the slow restraction method, due to the low viscosity of the ferrofluids, under various magnetic field strengths and the two configurations

Summary

Introduction

As long as our model of society keeps consuming products derived from crude oil, oil spills and discharges will be unavoidable. They must be remediated to prevent their immediate and longterm detrimental impact on ecosystems’ health and severe economic consequences for the affected zones. Zahn et al [6] proposed a magnetic clean-up process consisting of mixing synthesized magnetic nanoparticles and dispersing them in oil-polluted water in a vessel to form a ferrofluid either in the oil-phase or in the water-phase.

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Conclusion