A novel operational method of continuous foam separation, in which metal and/or surfactant solutions were injected into the rising foam bed, has been applied to the Au(III) recovery from binary metal solutions with Cu(II). The effects of experimental parameters, such as an air flow rate, metal concentration and solution acidity, were discussed in terms of the percent recovery and the separation factor of Au(III). A nonionic surfactant, polyoxyethylene nonyl phenyl ether, used in this study showed a strong affinity to Au(III) in HCl media and played a double role of foam-producing and metal collecting reagent. By injecting a metal solution to the foam bed, the recovery of Au(III) was improved due to the efficient contact between the metal and the foam surface counter-currently. On the other hand, injection of a surfactant solution facilitated the washing-out of the metals in the interstitial water between the adjacent foam, enhancing the separation of Au(III) from Cu(II). Furthermore, simultaneous injection of metal and surfactant solutions to the foam bed was also examined, and satisfactory results were obtained both in the yield and purity of Au(III). (c) 2006 Elsevier B.V. All rights reserved.