The combination of high value and widespread application of platinum to new designs and jewelry articles brings the inevitable requirement for recovery through refining procedures. The methods for recovering fine gold from process scraps and discarded jewelry articles have been known and practiced for centuries. Platinum has unique characteristics and inherent chemical properties that make it more difficult to recover than gold. Platinum refining procedures are required because the metal is more prone to contamination than other common jewelry materials. Gold, silver, silicon, phosphorous and iron can be incorporated into platinum from materials common to the fabrication process. The elevated temperatures required to melt and assemble platinum enhance the likelihood of melting and absorbing other elements. Process cleanliness contributes significantly to reducing contamination.

Unmixed high grade platinum can be treated in different processing circuit with fewer processing steps than complex mixes containing white and yellow golds. Melting and sampling of complex grades is impaired by the broad slushy solidification range with massive segregation from the inherent behavior of gold and platinum. Extremely hard and brittle materials often result from these complex scraps. This makes obtaining a representative sample both important and difficult.

Platinum assaying procedures are more complex than gold fire assaying. Often a combination of solid state XRF examination must be mixed with instrumentation techniques and /or classical wet chemistry separations to minimize the effects of PGM interference. This can result in protracted assaying process times.

Platinum refining has more processing steps, more incomplete separations, partial recovery, hydrolysis to strip base metals out before platinum recovery and waste streams that require more treatment compared to gold.  Both high grade and complex mixes take considerably longer to treat than conventional gold materials. In the worst scenario, a complex mix of platinum and gold scraps can require 35 processing steps over a period of 25-30 working days for recovery compared to eight steps requiring six days for gold separation.

From a technical perspective, platinum is a more difficult metal to recover from jewelry process scraps than gold.
 

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Technical Aspects of Platinum Refining
Greg Normandeau • Imperial Smelting & Refining Co. Ltd.

This is an abbreviated version of the original work. For full technical details, please consult the original paper.