The use of non-cavitating coupling fluids for intensifying sonoelectrochemical processes

Md Hujjatul Islam; Bouzid Naidji; Loic Hallez; Abdeslam Et Taouil; Jean-Yves Hihn; Odne S Burheim; Bruno G Pollet

doi:10.1016/j.ultsonch.2020.105087

The use of non-cavitating coupling fluids for intensifying sonoelectrochemical processes

Ultrason Sonochem. 2020 Sep:66:105087. doi: 10.1016/j.ultsonch.2020.105087. Epub 2020 Mar 23.

Authors

Md Hujjatul Islam¹, Bouzid Naidji², Loic Hallez², Abdeslam Et Taouil², Jean-Yves Hihn³, Odne S Burheim¹, Bruno G Pollet⁴

Affiliations

¹ Hydrogen Energy and Sonochemistry Research Group, Department of Energy and Process Engineering, Norwegian University of Science and Technology (NTNU), NO-7491 Trondheim, Norway.
² Institut UTINAM UMR 6213 CNRS, Université de Bourgogne Franche Comte, 16 route de Gray F25030, Besançon Cedex, France.
³ Institut UTINAM UMR 6213 CNRS, Université de Bourgogne Franche Comte, 16 route de Gray F25030, Besançon Cedex, France. Electronic address: jean-yves.hihn@univ-fcomte.fr.
⁴ Hydrogen Energy and Sonochemistry Research Group, Department of Energy and Process Engineering, Norwegian University of Science and Technology (NTNU), NO-7491 Trondheim, Norway. Electronic address: bruno.g.pollet@ntnu.no.

PMID: 32234676
DOI: 10.1016/j.ultsonch.2020.105087

Abstract

For the first time, we have investigated the beneficial effects of non-cavitating coupling fluids and their moderate overpressures in enhancing mass-transfer and acoustic energy transfer in a double cell micro-sonoreactor. Silicon and engine oils of different viscosities were used as non-cavitating coupling fluids. A formulated monoethylene glycol (FMG), which is a regular cooling fluid, was also used as reference. It was found that silicon oil yielded a maximum acoustic energy transfer (3.05 W/cm²) from the double jacketed cell to the inner cell volume, at 1 bar of coupling fluid overpressure which was 2.5 times higher than the regular FMG cooling fluid. It was also found that the low viscosity engine oil had a higher acoustic energy value than that of the high viscosity engine oil. In addition, linear sweep voltammograms (LSV) were recorded for the quasi-reversible Fe^2+/Fe³⁺ redox couple (equimolar, 5 × 10^-3 M) on a Pt electrode in order to determine the mass-transport limited current density (j_lim) and the dimensionless Sherwood number (Sh). From the LSV data, a statistical analysis was performed in order to determine the contribution of acoustic cavitation in the current density variation |Δj|_average. It was found that silicon oil at 1 bar exhibited a maximum current density variation, |Δj|_average of ~2 mA/cm² whereas in the absence of overpressure, the high viscosity engine oil led to a maximum |Δj|_average which decreased gradually with increasing coupling fluid overpressure. High viscosity engine oil gave a maximum Sh number even without any overpressure which decreased gradually with increasing overpressure. The Sh number for silicon oil increased with increasing overpressure and reached a maximum at 1 bar of overpressure. For any sonoelectrochemical processes, if the aim is to achieve high mass-transfer and acoustic energy transfer, then silicon oil at 1 bar of overpressure is a suitable candidate to be used as a coupling fluid.

Keywords: Asymmetric cavitation; Coupling fluid; Double cell sonoreactor; Mass transfer; Sonoelectrochemistry.