Facilitated transport of silver and copper from cyanide solutions through a supported liquid membrane (SLM) containing K+-crown ether as a carrier is described. The SLM used is a thin porous polypropylene (Celgard 2500, 2400) membrane impregnated with dibenzo-18-crown-6 (DB18C6), diaza-18-crown-6 (DA18C6), hexathia-18-crown-6 (HT18C6) and hexaaza-18-crown-6 (HA18C6) dissolved in a mixture of ethanol/chloroform (v/v). K+-crown ether showed a high efficiency to carry silver and copper as Ag(CN)(3)(2-) and Cu(CN)(4)(3-) species through the 3 of SLM. However, the mass flux of both silver and copper ions decreases when concentration cyanide ions in the feed phase increases due to the difference in stability of the complexes M(CN)(n)(n-) (M = Ag, Cu) when n increases from 2 to 4. This was related to the partition of the species in the aqueous phase using a theoretical model.