The extraction of copper(II) from nitrate/nitric acid aqueous solutions using Acorga M5640 has been studied. The metal extraction rate has been examined and also the effect of the aqueous pH, and metal and extractant concentrations. The increase of temperature increases copper extraction (DeltaH(0) = 16.4 kJ mol(-1)). Numerical treatment of the data indicated that the extracted species can be represented by the general stoichiometry CuR2 (R being the active substance of the extractant) with log K-ext = 2.11 +/- 0.09. The copper loading isotherms were obtained at 0.1 and 0.5 M nitric acid concentrations and 20 degreesC, whereas the stripping isotherm was obtained at 45 degreesC and using a solution of 180 g l(-1) sulphuric acid as strippant for copper. The oxime becomes degraded under prolonged contact time with nitric acid solution, but not with sulphuric acid.