Publication: Marcoscopic and microscopic motion of iron oxide magnetic nanoparticles stabilized pickering emulsion magnetophoresis at low field gradient
Date
2020-04-01
Authors
Tham, Foo Kean
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Abstract
A magnetic responsive of magnetic Pickering emulsion (MPE) was synergistically stabilized by the iron oxide nanoparticles (IONPs) coated by poly(sodium 4-styrenesulfonate) (PSS) and cetrimonium bromide (CTAB) as well as the adjacent CTAB molecules. In this project, MPE, IONPs, IONPs-PSS and IONP-PSS-CTAB were synthesized with their chemical, physical and magnetism properties thoroughly characterized. The synthesized MPE was studied under two main scales: (1) macroscopic and (2) microscopic experiment for the motion of MPE. For macroscopic experiment, the changing of turbidity of the MPE suspension was recorded by a digital camera using intervalometer. Whereas, a bright field optical microscope was employed to study the microscopic behavior of the Pickering emulsion. All images analysis were performed by standard technique using Image J. At the macroscopic scale, the magnetic separation efficiency of MPE at 90 % was achieved within 30 minutes for all condition. However, the colloidal stability of MPE at pH 10 was the lowest as compared to pH 3 and deionized water conditions. MPE at pH 10 required the shortest time for achieving the highest separation efficiency. Hence, MPE at pH 10 experienced cooperative magnetophoresis as it could be irreversible flocculated during magnetophoresis. Besides that, the MPE didnโt deform and coalescence under the magnetic field, B of 0.26 T~0.66 T and magnetic field gradient (๐๐ต๐๐งโ), โ๐ต of 52.07 T/m~ 95.74 T/m during macroscopic study. At the microscopic scale, different diameters (2.5 ฮผm~7.5 ฮผm) of emulsion droplets of MPE were migrated under magnetic field gradient (๐๐ต๐๐งโ), โB of 98.38 T/m. The largest droplets (7.5 ฮผm) required the shortest time to achieve the highest terminal velocity. Moreover, magnetophoresis analysis also concluded that monolayer of magnetic nanoparticles (IONPs-PSS-CTAB composites) was formed for the all sizes of emulsion droplets. Magnetophoresis analysis also showed that the surface coverage of IONPs composites on the emulsion droplets was coincided with the high positive zeta potential of MPE. This is because the CTAB molecules occupied the other large proportions of the surface of emulsion droplets in addition IONPs-PSS-CTAB. The successful of magnetophoresis of new synthesized MPE also contributed a great prospect for the oil recovery to prevent the loss of energy source.