Using the HClO₄-H₂O₂ System for Efficient Platinum Leaching: Optimal Conditions and Kinetics

Area of Science:

• Metallurgy and Materials Science
• Chemical Engineering
• Geochemistry

Background:

• Platinum is a valuable precious metal with significant natural reserves.
• Refractory minerals, particularly silicates, contain disseminated native platinum.
• Current processing methods are limited by the refractoriness of these minerals.

Purpose of the Study:

• To investigate the kinetics of platinum leaching using perchloric acid and hydrogen peroxide.
• To determine optimal conditions for efficient platinum extraction from refractory sources.
• To elucidate the mechanism governing the platinum leaching process.

Main Methods:

• Dissolution experiments using small, irregularly shaped high-purity platinum pieces.
• Kinetic analysis of leaching rates under varying temperatures and reagent concentrations.
• Thermodynamic and experimental validation of the proposed leaching mechanism.

Main Results:

• Leaching rate increases with temperature and perchloric acid concentration.
• An optimal hydrogen peroxide to perchloric acid ratio (≈2.5) was identified for maximizing kinetics.
• Optimal conditions determined as ≈70°C, 3 M HClO4, and 7.2 M H2O2, achieving elevated recoveries.

Conclusions:

• The platinum leaching process is controlled by a mixed mechanism involving diffusion and surface chemical reactions.
• The proposed mechanism highlights the role of chlorine gas and silicate structure weakening for novel extraction.
• This method offers a feasible approach for extracting platinum from previously inaccessible refractory minerals.