Electrochemical removal of cadmium from dilute aqueous solutions using a rotating cylinder electrode of wedge wire screens

Abstract

Rates of mass transfer at rotating cylinder electrodes of wedge wire screens were studied by measuring the limiting current for the cathodic reduction of ferricyanide as test reaction. The experimental data are well correlated by an empirical expression between the Sherwood number and the Reynolds number, both in terms of the internal slot opening as characteristic length, and including two additional dimensionless parameters in order to characterize the geometry of the screens. The performance of an undivided electrochemical batch reactor with a rotating cylinder cathode of wedge wire screens was tested analyzing the cadmium removal from dilute solutions. The effect of cathodic applied potential and size of the screen is studied. Taking into account the residual cadmium concentration the best results were obtained for a cathode potential of -1.1 V vs. SCE at 700 rpm, where the cadmium concentration decreased from 54 to 0.9 mg l-1 after 30 min of electrolysis with a specific energy consumption of 10.7 kWhkg-1 and a normalized space velocity of 3.54 h-1.