Co-extraction of cations and anions by calix4arene derivatives

摘要

Solvent extraction is used increasingly in extractive hydrometallurgy. Conventionally, for base metal recovery, metal cations are transferred selectively to a water-immiscible phase using ligands as ion-exchangers which release an equivalent number of cations, usually protons, back to the aqueous feed solution. Here we focused on a new type of extractant, polytopic zwitterionic ligands, which transfers metal salts into a water-immiscible phase. The systems discussed have metal-coordinating sites based on alkoxycalixarene derivatives and the anion-binding sites are provided by sulfamides or acetamides groups. These new reagents provide an alternative strategy for the concentration and separation of the metal values which eliminates the necessity of proton transfer, thus opening new flow sheets with good materials balances. In many cases anion- and cation-loading prove to be co-operative processes.