Applications of electrochemical technology involving low reactant concentrations often require electrodes with high mass transport rates and specific surface areas to increase cross-sectional current densities and optimise capital and operating costs. For electrodeposition of metals from dilute solutions, cathode feeder electrodes contacting unconsolidated beds of moving, conducting particles that can grow, achieve these requirements, and enable continual harvesting of the metallic product by hydraulic transport from the bed of the particles, the relative motion of which may facilitate adherent and coherent deposit morphologies. One design option, shown schematically in Fig.1, is a circulating particulate bed electrode [1,2], for which experimental results will be reported and compared with model predictions for recovery of:
1. low concentrations of platinum from aqueous iodide solutions with simultaneous generation of tri-iodide on a carbon felt anode (Fig.1);
2. metals from acidic aqueous chloride solutions, produced by the leaching of waste electrical and electronic equipment (WEEE), containing precious metals (Ag, Au, Pd) in low concentrations and base metals (Cu, Pb, Sn etc.) in high concentrations.