Leaching of gold and palladium with aqueous ozone in dilute chloride media

Abstract The recycling of gold and palladium from metallic scraps can be carried out by ozone-leaching at ambient temperature and low (∼0.1 M) H+ and Cl− concentrations. Rh and Pt remain un-reacted, whereas metals such as Cu, Ni, Ag, can be previously eliminated through O2/H+ and O2/O3/H+ leaching pretreatments. Gold and palladium are dissolved in O3/Cl−/H+ with formation of AuCl4− and PdCl42−. Leaching studies showed a passive region, basically located at  2, as consequence of the influence of the [H+] on transfer control. The electric power consumption associated with O3 generation was in the range 4–8 kWh/kg metal leached.

[1]  E. Briner,et al.  Détermination des solubilités de l'ozone dans l'eau et dans une solution aqueuse de chlorure de sodium; calcul des solubilités de l'ozone atmosphérique dans les eaux , 1939 .

[2]  A. V. Zosimov,et al.  Acid Catalysis in Reaction of Ozone with Chloride Ions , 2003 .

[3]  J. Hoigne,et al.  Rate constants of reactions of ozone with organic and inorganic compounds in water—I. Non-dissociating organic compounds , 1983 .

[4]  M. Rodahl,et al.  X-ray photoemission spectroscopy study of UV/ozone oxidation of Au under ultrahigh vacuum conditions , 1997 .

[5]  D. King.  Oxidation of gold by ultraviolet light and ozone at 25 °C , 1995 .

[6]  A. V. Zosimov,et al.  Interaction of Ozone with Sodium Chloride — a Possible Additional Source of Chlorine in the Atmosphere , 2002 .

[7]  G. R. Hill,et al.  The Kinetics and Mechanism of Hydroxide Ion Catalyzed Ozone Decomposition in Aqueous Solution1 , 1950 .

[8]  H. Tomiyasu,et al.  Kinetics and mechanism of ozone decomposition in basic aqueous solution , 1985 .

[9]  A. Roca,et al.  Leaching of metallic silver with aqueous ozone , 2005 .

[10]  G. Zimmerman,et al.  Equilibria and Spectra of Aqueous Chlorine Solutions , 1957 .

[11]  J. Staehelin,et al.  Rate constants of reactions of ozone with organic and inorganic compounds in water—III. Inorganic compounds and radicals , 1985 .

[12]  A. V. Zosimov,et al.  Catalysis of the reaction of ozone with chloride ions by metal ions in an acidic medium , 2005 .

[13]  L. B. Yeatts,et al.  The Kinetics of the Reaction of Ozone and Chloride Ion in Acid Aqueous Solution , 1949 .