How to Extract Gold, Platinum, and Palladium Using Aqua Regia

Aqua regia is a powerful and versatile mixture of hydrochloric acid (HCl) and nitric acid (HNO3) that can dissolve noble metals. This article provides a detailed guide on the process of extracting gold, platinum, and palladium from metallic scraps using this technique.

Materials Needed

Aqua regia (3 parts HCl to 1 part HNO3) Hydrogen peroxide (HO2) Sodium metabisulfite or another reducing agent Distilled water Glass beakers and stirring rods Filtration equipment Safety equipment such as gloves, goggles, and a fume hood

Steps to Extract Gold, Platinum, and Palladium

Preparation of Aqua Regia

:n - Carefully mix 3 parts concentrated hydrochloric acid with 1 part concentrated nitric acid in a fume hood. Always add acid to water, never the reverse, and handle with caution.

Dissolving the Metals

:n - Place the metal scrap containing gold, platinum, and palladium in a glass beaker and add aqua regia. Heat gently if necessary but avoid boiling. The metals will dissolve, forming a solution of chlorides.

Filtration

:n - After the metals have dissolved, filter the solution to remove any undissolved materials. Use filter paper and a funnel for this step.

Precipitating Gold

:n - To recover gold, add a reducing agent like sodium metabisulfite to the filtered solution. Gold will precipitate out as a solid.

Separating Platinum and Palladium

:n - To separate platinum and palladium, use hydrogen peroxide. Add it to the solution. Palladium will precipitate first as palladium(II) chloride, followed by platinum as a different compound. Adjust the pH as needed to optimize separation.

Filtration and Washing

:n - Filter out the precipitated metals. Wash the precipitates with distilled water to remove any residual chemicals.

Drying and Melting

:n - Dry the collected precipitates and then melt them using a furnace or torch to obtain pure metal ingots.

Safety Precautions

Always work in a well-ventilated area or fume hood. Wear appropriate personal protective equipment (PPE) including gloves and goggles. Be mindful of the hazardous nature of acids and the fumes produced during the process.

Conclusion

This is a simplified overview and should be approached with caution and proper understanding of chemistry. If you are not experienced with chemical processes, consider consulting a professional or conducting this work in a controlled laboratory setting.