The effect of the solution flow rate on the final mass of metals deposited into a porous electrode at individual and joint deposition. Rear delivery of solution

Abstract

Calculations in terms of the model of metal codeposition into a porous electrode (PE) and experimental measurements are used for studying how the flow rate m v and the volume of circulating solution at its frontal delivery affect the final mass of the cathodic deposit and its spatial distribution. For both individual and joint deposition of metals, the correlation between the final mass of the cathodic deposit m f and the uniformity of its distribution in PE is demonstrated: the more uniform the deposit distribution the higher its final mass. Due to peculiarities of the frontal delivery (the fixed position of the maximums of polarization and metal concentration and the same direction of their shift within the PE), the dependence of the final deposit mass on the volume flow rate demonstrates a very flat maximum shifted to sufficiently high m v. The increase in cathodic polarization and the transition to circulation with a small solution volume lead to the analogous shift. As a result, for the frontal delivery, the region of high flow rates turns out to be relatively more advantageous for the metal deposition into PE. For codeposition of silver and copper from their alkaline thiosulfate solution at the frontal solution delivery, the qualitative agreement between experimental and calculated m f = f(m v) dependences is demonstrated.