Reverse Micelle Mediated Bulk Liquid Membrane Separation of Platinum Gold and Silver From Real Samples

Abstract

Simple and selective reverse micelle mediated bulk liquid membrane extraction procedure is developed for the separation and simultaneous pre-concentration of precious metals from valuable wastes like spent auto mobile catalytic converters and gold jewelry washings. Quantification has been carried out using inductively coupled plasma optical emission spectrometry (ICP-OES). Tri octyl methyl ammonium chloride (TOAC), a cationic hydrophobic surfactant, forms reverse micelles after dissolution in trichloroethylene facilitating the extraction of platinum, gold and silver ions into the bulk liquid membrane. The procedure is based on the formation of extractable hydrophobic ion-associates between TOAC cationic reverse micelles and anionic metal ions. These hydrophobic ion-associates which are transported into the bulk organic membrane from an aqueous feed phase are subsequently stripped into a receiving solution in a unitary process. Optimum conditions for the overall transport efficiency of precious metals have been evaluated. The accuracy of the procedure was validated by analyzing GBWAu-18 ore from faulted zone and PTM-1a nickel-copper sulphide matte certified reference materials. The procedure has been applied to spent catalytic converters and jewellery washings.

Supplemental materials are available for this article. Go to the publisher's online edition of Separation Science & Technology to view the supplemental file.

Keywords:

• precious metals
• reverse micelles
• separation and pre-concentration
• spent catalytic converter
• tri octyl methyl ammonium chloride (TOAC)

ACKNOWLEDGEMENTS

The authors are thankful to Dr. J. Arunachalam, Head (CCCM/BARC) and Dr. Sunil Jai Kumar, Head UTAS (CCCM/BARC) for their keen interest and consistent encouragement during this work and K. Madhavi for help during sample collection and digestion. One of the authors, T. Revathi Reddy, is thankful to UGC for providing her the grant to carry out this work.

Notes

^a Values are mean of six measurements ± standard deviation.

^a  t _0.95 = 3.18, n = 4 and s = standard deviation.

^b Certified values are given in parenthesis

^c Not detected.

^d Values are obtained by mixed micelle cloud point extraction ref (33).

^e Values are in µg mL⁻¹.

^f Values are obtained by using nonionic surfactant based cloud point extraction ref (34,35).