Selective Extraction of Gold with Polymeric Inclusion Membranes Based on Salen Ligands with Electron- Accepting Substituents

Abstract

Salen-type ligands with electron-accepting substituents on the aromatic ring were synthesized. These ligands were used as extractant agents in polymeric inclusion membranes for the extraction of metal ions from aqueous solutions. Measurements of the membrane potential indicated selectivity of the membrane, which was confirmed by the quantification of the extracted metal. Ten types of metal ions were studied to establish the selectivity of each membrane. Salen-type ligands had higher selectivity to gold than to other metals and allowed for the extraction of acceptable percentages of this metal. The results showed that the percentage of extracted gold depends on the type of substituent present in the ligand`s aromatic ring, the pH of the working solution and the area of the membrane. There was no effect of membrane thickness on the metal extracted. The time required to reach a certain extraction percentage decreased considerably as the membrane area increased.