Mass transfer studies at three-dimensional rotating cylinder electrodes

J.M. GRAU; J.M. BISANG

Costa Verde, R. J. - Brasil

Congreso; 2nd Mercosur Congress on Chemical Engineering 4thMercosur Congress on Process Systems Engineering – ENPROMER; 2005

Abstract. The increasing requirements of legal limitations for environmental protection require the development of reliable and cost-effective processes for the treatment of effluents with small concentration of dangerous species. The electrochemical treatment of effluents can be efficiently performed with the use of the rotating cylinder electrode, where the good mass-transfer conditions are achieved by the movement of the electrode. Another strategy to obtain a high space time yield is the use of electrochemical reactors with threedimensional electrodes or the combination of the two above concepts: that is, a rotating three-dimensional electrode. In this work, mass transfer has been studied at rotating cylinder electrodes of expanded metal and rotating packed-bed of screens using the reduction of ferricyanide or copper deposition as test reactions. When the surface electrode area is not changed by the electrochemical reaction, the experimental data are well correlated by an empirical expression between the Sherwood number and the Reynolds number, both in terms of the hydraulic diameter as characteristic length, and additional dimensionless parameters must be included in order to characterize the geometry of the electrode material. For the case of metal deposition the mass-transfer coefficients may be estimated by the Holland expression. Comparisons of the mass-transfer performance of the electrodes with other three-dimensional structures are made. Keywords: mass transfer, expanded metal, rotating cylinder electrode.