Extraction of copper from aqueous solutions with carboxylic acids

The distribution equilibrium data at 25°C for the extraction of copper from aqueous solutions, containing sodium nitrate or sodium sulphate, by carboxylic acids using toluene, benzene and carbon tetrachloride as diluents have been measured. The carboxylic acids used are n-myristic, n-lauric and n-capric. The results obtained led to the conclusion that the composition of the extracted species corresponds to (CuR₂.HR)₂, being irrespective of both the nature of organic phase and the aqueous phase. The addition of sodium sulphate, instead of sodium nitrate, decreases the extraction efficiency due to the formation a CuSO₄ ion-pair into the aqueous phase. The diluent effect has been related to the activity of the dimerised carboxylic acid in the diluent.