Thickening of aqueous nanoparticle suspension using DC electric field

Abstract

It is challenging to thicken a well-dispersed nanoparticle suspension without changing the particle dispersion state. In our previous report, we demonstrated that several kinds of particles can be quickly settled from solutions by applying a DC electric field. Thus, we attempted to gravitationally thicken a well-dispersed aqueous nanoparticle suspension using a DC electric field instead of a flocculant. To increase the recovery ratio of nanoparticles, it is necessary to prevent particle deposition on the electrodes. Therefore, in this study, we investigated the effect of switching the direction of the DC electric field after certain intervals, and clarified the effect of the switching time on the concentration and particle size of the concentrated suspension. The concentration of an alumina nanoparticle suspension quickly increased by a factor of at least three by applying the DC electric field. In addition, the particle size measured by dynamic light scattering after the application of the DC electric field was almost the same as the nominal average particle size, suggesting that the particles in the aggregates did not overcome the potential barrier and redisperse when the field was removed. Therefore, the use of the DC electric field successfully thickened the aqueous nanoparticle suspension and the particles in the thickened suspension were well dispersed. The findings show that the proposed method has the potential to change material fabrication processes, enabling a dilute nanoparticle suspension prepared by synthesis to be easily and rapidly concentrated.