The removal of zinc and chromium ions from aqueous solutions was investigated in the present study by the application of a two-stage separation process, termed sorptive flotation. The first stage consists of the metal ions sorption onto an appropriate sorbent material, followed by successive flotation as the second stage. The sorbent material was either laboratory prepared goethite, or in situ generated ferric hydroxide. The biologically produced surface active agents Surfactin-105 and Lichenysin-A, were applied as flotation collectors for the separation of the metal-loaded sorbents. The main studied parameters were the concentrations of sorbent materials, as well as of biosurfactants. Under the application of optimised conditions better floatabilities of metal-laden sorbents were obtained, when using the biosurfactants in comparison with the application of conventional (chemically produced) surfactants (sodium dodecyl sulphate or dodecylamine) examined under similar conditions. (C) 2003 Elsevier Ltd. All rights reserved.