The extraction of cadmium(II) by Cyanex 923 (a mixture of alkylphosphine oxides) in Solvesso 100 from hydrochloric acid solution has been investigated. The extraction reaction is exothermic. The numerical analysis of metal distribution data suggests the formation of CdCl2.2L, HCdCl3.2L and H2CdCl4.2L (L = ligand) in the organic phase. The results obtained for cadmium(II) distribution have been implemented in a solid-supported liquid membrane system. The influences of feed phase stirring speed (400-1400 min(-1)), membrane composition (carrier concentration: 0.06-1 mol dm(-3)) and metal concentration (0.01-0.08 g dm(-3)) on cadmium transport have been investigated. (c) 2005 Society of Chemical Industry