Mass transfer characteristics of a novel gas-evolving electrochemical reactor

Mass transfer coefficients were measured for the deposition of copper from acidified copper sulphate solution at a vertical-plate cathode stirred by the oxygen evolved at a coplanar, vertical-plate lead anode placed upstream from the cathode. The variables studied were: oxygen discharge rate, electrolyte concentration and height of the cathode. The cathodic mass transfer coefficient was increased by a factor of the order of 2 to 5 over the natural convection value depending on the rate of oxygen discharge at the lead anode. The relationship between the mass transfer coefficient and the oxygen discharge rate was found to be logK=a+0.296 logV.The mass transfer coefficient was found to decrease initially with increasing electrode height, but then reached a constant value independent of further change in electrode height. A new, modified parallelplate reactor stirred by the counter electrode gases is described. The advantage of the design is that it offers more efficient stirring with no added power consumption. Details of the design are discussed.Nomenclature C concentration of CuS0₄ (mol cm^–3) - F Faraday's constant - h electrode height (cm) - K mass transfer coefficient (cm s^–1) - l _L limiting current density (A cm^–2) - V gas discharge rate (cm s^–1) - z number of electrons involved in the reaction On leave from the Department of Chemical Engineering, Faculty of Engineering, Alexandria University, Alexandria Egypt.