Abstract
Foam separation of Au(III) from its hydrochloric acid solutions was studied in a batch mode 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 played a double role of foam-producer and metal-collector. Effects of experimental parameters, such as the length of drainage section of the column, concentration of the surfactant and the metal, air flow rate and solution temperature, were discussed in terms of the recovery and the enrichment of Au(III). The recovery increased with an increase in the concentration of surfactant and in air flow rate, while the enrichment improved with decreasing air flow rate and increasing the length of drainage section. The behavior of Au(III) adsorption onto the foam was also analyzed in terms of the surface excess, and the Freundlich’s adsorption isotherm was successfully applied to the system. Moreover, the selective separation of Au(III) from several heavy metals and the application of cloud point extraction to the present foamate solution were also carried out with the resultant enrichment ratio of 59.
Highlights
Conventional hydrometallurgical processes for recovering precious metals generally consist of multiple steps of dissolution, conditioning and precipitation
Gold was found to be strongly complexed with the nonionic surfactants in hydrochloric acid media, and we have examined the separation of gold in such unit operations as solvent extraction [8], cloud point extraction [9] and micellar-enhanced ultrafiltration [10]
Increased temperature prevents the stable formation of foam and the subsequent adsorption of the metal on the foam surface, as ascertained by a decrease in the foamate volume recovered. These results indicate that careful control of temperature must be introduced in the foam separation process with nonionic surfactants
Summary
Conventional hydrometallurgical processes for recovering precious metals generally consist of multiple steps of dissolution (leaching), conditioning and precipitation. These are labor-intensive and time-consuming, and much work has been conducted on the development of alternative methods including solvent extraction and ion exchange. Gold exists exclusively as tetrachloro-anion (AuCl4-) [1] Ion pair extractants such as amine salts are utilized to extract this anionic species [2,3], while solvating extractants including methyl isobutyl ketone [4] and dibutylcarbitol (diethyleneglycol dibutyl ether) [1] are adopted in the extraction of its parent acid, tetrachloroauric acid (HAuCl4).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: Journal of Minerals and Materials Characterization and Engineering
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
