Electrolytic Recovery of Gallium from Dilute Solutions Employing Microelectrodes

Abstract

The recovery of gallium from dilute solutions is known to be slow and inefficient due to competing hydrogen evolution and the limitations of mass transport. Methods used to improve the process include pulse plating, inhibition of hydrogen evolution by suitable additives, increasing the pH, and conducting the process at temperatures above the melting point of gallium. In the present work, an alternative approach was taken employing microelectrodes to enhance the rate of mass transport and thus to increase the rate of gallium recovery. Potentiostatic plating and stripping experiments were performed using electrodes ranging in diameter from 1 cm down to 45 μm. The effect of electrode diameter on the rate and efficiency of the plating of gallium was studied at different potentials and under different conditions of mass transport. The effect of plating time was also determined, and the conditions for the optimum recovery of gallium in terms of the overall rate as well as the current efficiency were evaluated. Carbon fiber epoxy composites can serve as ensembles of microelectrodes. It was shown that, with a typical radius of 3–5 μm for the individual fibers, considerable enhancement of the rate of recovery of metals from dilute solutions can be expected.