Platinum Refining: From Leaching to Roasting

Platinum refining involves a series of steps to obtain high-purity platinum. Here's a concise overview:

1. Leaching: Platinum and other metals are dissolved in a solution with strong oxidants like aqua regia and NaClO3. Silver forms a precipitate while platinum dissolves. Reaction:

3Pt+2NaClO3+18HCl→3H2PtCl6+2NaCl+6H2O3Pt+2NaClO3​+18HCl→3H2​PtCl6​+2NaCl+6H2​O

2. Neutralization: Adjust the high-acidity leaching solution to pH 1 using NaOH and wash the residue with hydrochloric acid.

3. Platinum Precipitation: Add ammonium chloride to the solution until no more yellow precipitate forms. Then, cool, filter, and wash the residue with 10% ammonium chloride. Reaction:

H2PtCl6+2NH4Cl→(NH4)2PtCl6↓+2HClH2​PtCl6​+2NH4​Cl→(NH4​)2​PtCl6​↓+2HCl

4. Roasting: Heat the filtered residue to decompose ammonium chloroplatinate into sponge platinum. Repeat chlorination, neutralization, and roasting until pure platinum powder is obtained.

(NH4)2PtCl6→Heating3Pt+2NH4Cl+16HCl+2N2↑(NH4​)2​PtCl6​Heating​3Pt+2NH4​Cl+16HCl+2N2​↑

Platinum refining is critical for various industrial applications, ensuring the metal's purity and quality.