A Study of the Variables in the Optimisation of a Platinum Precipitation Process

This study investigated possible ways to improve the efficiency of the platinum precipitation process using ammonium chloride by reducing the platinum content reporting to the effluent. The ore treated consist of five platinum group metals namely, ruthenium, rhodium, iridium, platinum, palladium and a precious metal gold. Gold, ruthenium, rhodium and iridium were extracted prior the platinum precipitation process. Temperature, reducing agent, flow rate and potential difference were the variables controlled to determine the operation conditions for optimum platinum precipitation efficiency. Hydrogen peroxide was added as the oxidizing agent at the temperature of 85-90oC and potential difference of 700-850mV was the variable used to check the oxidizing state of platinum. The platinum was further purified at temperature between 60-65oC, potential difference above 700 mV, ammonium chloride of 200 l, and at these conditions the platinum content reporting to the effluent was reduced to less than 300ppm, resulting in optimum platinum precipitation efficiency and purity of 99.9%.

Authors:

• Tebogo Phetla
• Edison Muzenda
• M Belaid

Keywords:

• Platinum Group Metals (PGM)
• Potential difference
• Precipitation
• Redox reactions.

References:

[1] F. L. Bernardis, A.R. Grant & S.D. Sherrrington, "A review of methods
of separation of the platinum-group metals through their chlorocomplexes,"
Reactive & functional polymers, vol. 65, pp. 205-207, 2005.
[2] F. R. Hartley (ed), "Chemistry of the Platinum Group Metals, Recent
Development," Elsever Science Publisher, pp. 9-30, 1991.
[3] C. R. M. Rao & G. S. Reddi ," Platinum group metals (PGM);
Occurrence, use and recent trends in their determination," Hyderabad
500068, India, vol.19. no.9,2000.
[4] D. McDonal, "A History of Platinum," Johnson Matthey and Co.Ltd.,
London, 1960.
[5] P. Charlesworth, "Separating the Platinum Group Metals by liquid-liquid
extraction," Platinum Metals Rev., vol. 25, no. 31, pp. 106-112, 1981.
[6] J. L. Bray, Non-Ferrous Production Metallurgy. New York, Wiley&
Sons, 2nd Edition , 1947.
[7] L. Pauling, General Chemistry. New York Dover, 1988.
[8] G. B. Kauffman, Ammonium Hexachloroplatinate Inorganic Synthesis.
New York, Wiley and Sons, 1967.
[9] R. J. Angelic, Reagent for Transition Metals Complex and
Organometallic Synthesis. New York, Wiley and Sons, 1990.
[10] W. Watson, Phil. Trans., vol. 46, no. 584, 1951.
[11] W. Lewis, Phil.Trans., vol. 18, no. 638, 1755.
[12] D. Ms Donald, and L. B. Hunt, "A History of Platinum and its Allied
Metals," Johnson Matthey and Co.Ltd., Hatton Garden, London, 1982.
[13] G. G. Robson, "Platinum 1985," Johnson Matthey plc, 1985.
[14] Rustenburg Platinum Mines, "Productivity in Platinum Mining: A
Continuing Programme of Successful Development in Underground
Mechanisation," Platinum Metals Rev., vol. 24, no. 4, pp. 138-143,
1980.
[15] L. J. Cabri, "Platinum-Group Elements: Mineralogy, Geology and
Recovery," Canadian Institute of Mining and Metallurgy, vol. 23,
Montreal, 1981.
[16] D. W. Bullet, "The surface properties of platinum metals," Platinum
Metals Rev., vol. 23, no. 3, pp. 109 - 111, 1979.
[17] F. R. Hartley, "The Chemistry of Platinum and Palladium: With
particular reference to complexes of the elements," Platinum Metals
Rev., vol. 17, no. 3, pp. 105. 1973.
[18] W. P. Griffith, The Chemistry of the Rarer Platinum Metals.
Interscience, London 1967.