The enhancements in mass transfer coefficients due to the presence of spiral coil promoters in batch fluidized beds are presented in this paper. The variables studied are the flow rate of the electrolyte, the geometric parameters of the promoter-coil diameter (d(c)), pitch of the coil (p) and diameter of the coil wire (d(w)), void fraction, and particle diameter (d(p)). It is found that the mass transfer coefficient increased with increased flow rate and particle diameter. The increased pitch of the coil has decreased the mass transfer coefficient. The increase in coil diameter and diameter of the coil wire have increased mass transfer rates. (C) 2003 Elsevier B.V. All rights reserved.