Thermochemistry and oxidation potentials of the platinum group metals and their compounds

Goldberg, Robert N.; Hepler, Loren G.

doi:10.1021/cr60252a004

Cited by 98 publications

(30 citation statements)

References 77 publications

(112 reference statements)

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“…et al (1982). The stability data for solid PtS and PtSz were taken from Goldberg and Hepler (1968), and data for most of the other gaseous and solid species were obtained from the data banks CPDMRLDATA and CPDNBSDATA contained in the C.S.I.R.O-SGTE-THERMOCHEMISTRY system.…”

mentioning

confidence: 99%

The calculated solubility of platinum and gold in oxygen-saturated fluids and the genesis of platinum-palladium and gold mineralization in the unconformity-related uranium deposits

Jaireth

1992

Mineral. Deposita

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Thermodynamic calculations on the solubility of platinum and gold indicate that saline (1 m NaC1), fluids saturated with atmospheric oxygen can transport geologically realistic concentrations of platinum-groupelements (PGE), gold, and uranium as chloro-complexes. A number of calculations involving fluid-rock interaction suggest that the oxygen-saturated fluids flowing through rocks containing quartz, muscovite, kaolinite, magnetite and hematite, initially oxidize any magnetite to hematite, allowing subsequent batches of ore fluids to retain their high oxidation state. During their migration through the aquifer, the oxidizing fluids would move the oxidationreduction interface deeper into the aquifer, leaching and redepositing platinum and gold. The redissolution of earlier precipitated platinum and gold depends on the fluid/ rock ratio and the associated increase in the oxidation state. Therefore, lowering of fluid/rock ratios and/or mixing of the oxidized fluids with a large amount of reduced fluid will precipitate uranium, PGE, and gold. It is suggested that this model can explain the genesis of gold and PGE mineralization in the unconformity-related ura-

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mentioning

confidence: 99%

The calculated solubility of platinum and gold in oxygen-saturated fluids and the genesis of platinum-palladium and gold mineralization in the unconformity-related uranium deposits

Jaireth

1992

Mineral. Deposita

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“…However, Templeton [58,59] reported a value of E 0 ¼ 0.987 V from an HClO 4 solution at ionic strength I ¼ 4 mol L À1 which, when adjusted to zero ionic strength [59], yields E 0 ¼ 0.945 V. Other measurements by various investigators [60] have yielded E 0 ¼ 0.978 V AE 0.0005 V while polarographic [61] measurements confirmed the value of Izatt et al…”

Section: Oxidation States and Coordination Chemistrymentioning

confidence: 73%

Palladium Electroplating

Abys¹

2010

Modern Electroplating

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“…Though the iodide system has the lowest driving force for dissolution, this also corresponds to the lowest cell . Potential-pH diagrams for Pd-I-water and Pt-I-water systems at 25°C, I activity 1 M, dissolved metal activities 10 )5 M. Thermodynamic data sources: PdO, PtO, PtO 2 [11], PdO 2 calculated from [12], PdI 4 2) , PdI 6 2) , PtI 4 2) , PtI 6 2) [13]. All other species [12].…”

Section: Possible Process Chemistriesmentioning

confidence: 99%

Recovery of platinum group metals from secondary materials. I. Palladium dissolution in iodide solutions

Dawson

Kelsall

2006

J Appl Electrochem

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Thermodynamic predictions are reported for platinum and palladium in aqueous ammonia and iodide solutions, to define less aggressive conditions than used hitherto for leaching palladium and platinum from secondary materials. Cyclic voltammetry and amperometry of thin films of palladium, electrodeposited onto rotating vitreous carbon disc electrodes, indicated that partially oxidised adsorbed species passivated dissolution in aqueous ammonium sulfate. By contrast, dissolution rates in aqueous potassium iodide solutions were a significant fraction of that corresponding to the mass transport controlled rate of reduction of tri-iodide, which was demonstrated to be a suitable oxidant for the envisaged metal recovery process. However, iodide concentrations >1 M were required to achieve adequate solubility of the oxidation products, assumed to be PdI 4 2) ions, thereby avoiding inhibition by PdI 2 . The reduction of tri-iodide on palladium was very facile, with large exchange current densities and Tafel coefficients; two alternative mechanisms are proposed that fitted experimental results well. In addition, a kinetic model to predict dissolution rates of Pd in tri-iodide solutions gave good agreement with experimental data, provided an equilibrium constant of 10 )4.5 was used for the PdI 2 /PdI 4 2) reaction, rather than the value of 10 )2.8 derived from thermodynamic data.

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Thermochemistry and oxidation potentials of the platinum group metals and their compounds

Cited by 98 publications

References 77 publications

The calculated solubility of platinum and gold in oxygen-saturated fluids and the genesis of platinum-palladium and gold mineralization in the unconformity-related uranium deposits

The calculated solubility of platinum and gold in oxygen-saturated fluids and the genesis of platinum-palladium and gold mineralization in the unconformity-related uranium deposits

Palladium Electroplating

Recovery of platinum group metals from secondary materials. I. Palladium dissolution in iodide solutions

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