Oleylethoxycarboxylate--an efficient surfactant for copper extraction and surfactant recycling via micellar enhanced ultrafiltration.

The nonaoxyethylene oleylether carboxylic acid Akypo RO90 VG, a surfactant with ionic character at high pH and non-ionic character at low pH, has been investigated with respect to copper removal from aqueous streams via micellar enhanced ultrafiltration (MEUF) with subsequent copper and RO90 separation using the method of cloud point extraction (CPE). Almost quantitative Cu2+ removal is obtained in MEUF and more than 90% Cu2+ is separated from RO90 in CPE. The investigation of Cu(2+)/RO90 complexes with small-angle neutron scattering (SANS) shows almost no structural change of RO90 micelles in the presence of Cu2+. These results show the importance of the surfactant head group for optimizing the specific interaction with the ion to be extracted. This optimization and the ability to recycle the surfactant by a temperature variation and using the cloud point phenomenon is an elegant approach to achieve efficient metal ion extraction.