Continuous Recovery of Gold(III) via Foam Separation with Nonionic Surfactant

A continuous recovery of Au(III) via foam separation from its hydrochloric acid solutions was studied using a nonionic surfactant: polyoxyethylene nonyl phenyl ether having 20 ethylene oxide units (PONPE20). The surfactant showed a strong affinity to Au(III) in HCl media, and successfully played a dual role for foamproduction and metal-collection in the system. Experimental parameters examined were the feed flow rate, the foam height and the depth of bulk liquid phase. Under a standard condition, the percent recovery and the enrichment ratio of Au(III) were 54 % and 4.5, respectively. Using the adsorption isotherm of Au(III) obtained in a batch operation, these two values could be estimated against the feed flow rate which are in good agreement with the experimental ones. It was also found that about 90 % of Au(III) recovered in the foamate phase was transferred onto the foam surface and the rest was conveyed to the interstitial water between the foam. Highly selective recovery of Au(III) was achieved from multi-metals solution.