Micellar-enhanced ultrafiltration of gold(III) with nonionic surfactant

The micellar-enhanced ultrafiltration (MEUF) of gold(III) from dilute hydrochloric acid media has been studied using polyoxyethylene nonyl phenyl ethers (PONPEs) as a nonionic surfactant. The micelles entrap gold(III) ions in aqueous solutions due to a high affinity between the surfactant and the metal, and then are rejected by a ultrafiltration membrane having smaller pores than the size of the micelle, whereby a concentration of gold(III) can be realized in the retentate solution. The rejection efficiency of gold(III) increases with increasing surfactant concentration, ethylene oxide number of PONPE and the applied pressure as well as decreasing molecular weight cutoff (MWCO) of the membrane. Moreover, the MEUFs were applied to the mutual separation of heavy metal ions. It was found that the use of MEUF with PONPE10 provides higher selectivity to gold(III) than those with charged surfactants such as cetylpyridinium chloride and sodium dodecyl sulfate.