Solute Concentration Distribution in the Vicinity of Solid-Liquid Interface under the Imposition of a Time-Varying Force

Abstract

Mass transfer is often the rate determining step for solid-liquid reaction, such as an electroplating process in automotive industry and a refining process in metallurgical industry. The decrease of concentration boundary layer thickness through the excitation of convection is adapted to enhance the solid-liquid chemical reaction rate. Therefore, traditional methods excite a macro-scale flow in the bulk liquid. Because the concentration boundary layer exists in the velocity boundary layer, the traditional methods have the limitation in enhancing mass transfer rate. Therefore, a new method was proposed, which imposes force directly near the solid-liquid interface. In the past research, force, with or without an oscillating component was imposed near the solid-liquid interface during the dissolution of a Cu anode into a Cu²⁺ aqueous solution. The increase of Cu²⁺ concentration under the force imposition with oscillating component was suppressed compared to that by imposing the force without oscillating component just above the center of the anode. This research evaluated the dissolved Cu²⁺ concentration distribution and the liquid flow pattern in the whole vicinity of the solid-liquid interface under the force imposition with or without oscillation component. The results indicated that by imposing the force with oscillating component, the increase of the Cu²⁺ concentration was suppressed in the whole vicinity of the solid-liquid interface, and the Cu²⁺ concentration distributed more uniformly near the solid-liquid interface. This might be because of the excitation of circulating micro-scale flows near the side parts of the anode surface.