Characterization of flow distributions in liquid-liquid systems by MRI

SERIAL, M.R, VELASCO, M.I. SILLETTA, E.V, ACOSTA, R.H.; OVEJERO J M, DASSIE

Aarhus

Conferencia; EUROMAR Conference 2016; 2016

EUROMAR

Ion transfer at the interface between two immiscible electrolyte solutions (ITIES) is a very important physicochemical process, while reactions that occur at the interface between two immiscible liquids are common to many natural and industrial systems [1]. For instance, solvent extraction and phase transfer catalysis relay on optimized reactions at liquid-liquid interfaces. These can be additionally considered as useful biomembranes analogs, or for experimental investigation of cell membrane transfer processes. To perform quantitative electrochemical measurements at the interface, a nonconventional electrochemical cell is usually employed, where the interface is controlled by a small contact area between the two liquid phases [2], with flow induced through a convective flow generated by a spinning electrode. MRI is a suitable tool to study flow dynamics [3,4]. In this work we study the dynamics of two immiscible fluids (water and 1,2-dichloroethane, which is used as an organic phase) inside two-compartment electrochemical cell. To maintain a uniform surface polarization, the interface between the aqueous and the organic phase must remain stationary and planar during electrochemistry experiments. Therefore, no velocity patterns should be observed in the organic phase. 3D velocity maps of water inside the cell were acquired for different rotational speeds. Velocity fields for the liquid-liquid system were also measured, for different shapes of the interface. An optimal position for the interface, in terms of electrochemical experiments, could be determined from the obtained velocity patterns. [1] V. J. Cunnane and L. Murtomaki, ?Electrocatalysis and electrolysis in Liquid-Liquid Interfaces?. Theory and Methods, A. G. Volkov and D. W. Deamer, Eds., pp. 401?416, CRC Press, Boca Raton, Fla, USA, 1996.[2] V. Marecek, Z. Samec, and J. Koryta, ?Advances in Colloid and Interface Science?, vol. 29, no. 1-2, pp. 1?78,1988.[3]P.R. Moran, A flow velocity zeugmatographic interface for NMR imaging in humans. Magn Reson Imaging 1982;1(4):197?203.[4] M. Carpinella, M.I. Velasco, E.V. Silletta, J.M. Ovejero, S.A. Dassie, R.H. Acosta, Determination of flow patterns in a rotating disk electrode configuration by MRI, J. Electroanal. Chem., 750, 100 (2015).