DISSOLVED-OXYGEN CONCENTRATION IN A DIVIDED ROTATING CYLINDER ELECTRODE REACTOR

The steady-state mass balance for dissolved oxygen in a divided rotati ng cylinder electrode reactor was established. Cases involving the abs ence or presence of hydrogen evolution, as in, respectively, copper an d zinc deposition, were treated. The results show that the importance of the diffusion controlled oxygen reduction reaction on metal deposit ion current efficiency is considerably decreased at low electrolyte fl ow rates used industrially by separating the reactor with a membrane, thus preventing the oxygen formed at the anode from reaching the catho de. Further substantial gains are achieved if hydrogen evolution takes place in the reactor, allowing a very efficient desorption mechanism of dissolved oxygen, but the global effect on metal deposition current efficiency remains unfavorable. The influence of several parameters o n dissolved oxygen concentration inside the reactor and metal depositi on current efficiency, such as electrolyte how rate, mass transfer coe fficient, current density and inlet electrolyte dissolved gases concen tration (oxygen and hydrogen), is also discussed. Comparison with expe rimental data for copper and cadmium deposition show that the derived equations appear adequate, although more data is required to make a co mplete assessment. Finally, the derived equations allow optimization o f the rotating cylinder electrode reactor.