Removal of cadmium and production of cadmium powder using a continuous undivided electrochemical reactor with a rotating cylinder electrode

The behaviour of a continuous undivided electrochemical reactor with a rotating cylinder electrode under potentiostatic control is examined for the abatement of cadmium from synthetic sodium sulfate solutions with Cd(II) concentrations lower than 500 mgdm(-3) at a reactor inlet pH congruent to 7. The process was designed to convert the metal ions in solution to metal powder, which settles to the conical of the reactor and may be removed at intervals as a sludge by opening a drop valve. The effect of applied potential, inlet cadmium concentration, rotation speed and hydrogen evolution as side cathodic reaction on the 'figures of merit' of the reactor are analysed. The best results were obtained for cathode potentials in the range from -0.9V to -1.0V against the saturated calomel electrode. Therefore, when the rotation speed was 1000 rpm the space time yield and the normalized space velocity were 0.64 x 10(-2) mol m(-3) s(-1) and 0.89 h(-1) respectively, while the fractional conversion per pass was 35% with a current efficiency higher than 74%. The surface morphology of the deposits as a function of the process variables is also reported. (C) 2002 Society of Chemical Industry.