Cyanide as a copper leaching agent for the remediation of fouling of a supported liquid membrane by formamidine disulphide in thiourea medium

We have found in previous works that facilitated transport of copper from copper-thiourea leaching solutions was hampered by the formation of formamidine disulphide (a product of thiourea oxidation) which constitutes an obstacle for the complexation of copper(l) ions at the feed phase/membrane interface. The permeability factor of copper ion decreases when the concentration of thiourea increases. In the present work, the facilitated transport of copper becomes possible when cyanide is used as the leaching agent. On the other hand, the pH of the solution, as in the case of the thiourea medium, is a fundamental parameter for achieving high values of the permeability factor. pH I I is recommended to avoid at the same time the release of the highly toxic gas HCN.