Fluoride Precipitation of Cu Over Fe in a Selected pH Window

Fe is an impurity in most leach liquors. Its coexistence with copper in leaching solution of chalcopyrite (CuFeS2) which is the most important mineral of copper creates major extraction problems. Hydrochloric acid dissolves both copper and iron during chloride leaching of this mineral. Separation of Fe from Cu is thus necessary to obtain pure copper. This paper presents a novel method for precipitation of Cu over Fe from mixed chloride acidic liquors. Hydrofluoric acid is used as the major unraveling agent. Kinetic studies show that a second-order CuCl2 precipitation reaction with a chemical rate constant of k = 0.416 L/mol prevails the process at the room temperature. For validation of the results, precipitate characterization by x-ray fluorescence (XRF) and x-ray diffraction (XRD) and solution analysis by atomic absorption spectrometry (ABS) are performed. Nitrogen presence is shown to help separation of iron from copper. The optimum value of pH (1.09) is achieved when nitrogen helps parting of 99 % iron II ions in the solution and sole deposition of copper II chloride precipitate.