Gold refining is an essential process for obtaining pure gold from impure sources. Among various refining techniques, the Aqua Regia process is one of the most effective and widely used methods. It ensures high-purity gold (up to 99.99%) while maintaining safety and efficiency. In this blog, we will explore how the Aqua Regia process works, its advantages, and its technical aspects.

What is Aqua Regia?

Aqua Regia is a highly corrosive mixture of concentrated nitric acid (HNO₃) and hydrochloric acid (HCl). It is known for its ability to dissolve noble metals like gold and platinum. However, some metals such as titanium, iridium, ruthenium, tantalum, and osmium can resist its corrosive nature. The name "Aqua Regia" comes from Latin, meaning "Royal Water," as it has the unique ability to dissolve gold, the most precious of metals. The Aqua Regia process is one of the fastest and most effective gold refining techniques.

Why Use the Aqua Regia Refining System?

The Aqua Regia process is ideal for refining gold because:

✔️ It achieves a high purity level of 99.99%.​

✔️ It is economical and efficient for industries requiring high-standard gold production.​

✔️ The refining plant operates in a closed circuit, ensuring maximum safety by preventing direct exposure to harmful acids and fumes.​

✔️ The process is fast, taking less than 4 hours per refining cycle.

Step-by-Step Process of Gold Refining Using Aqua Regia

Step 1: Gold Dissolution

●Input: Impure gold is placed in a reactor with Aqua Regia.
●The mixture is heated to 100°C, then cooled to 65°C with a stirrer.
●Most metals dissolve in the solution, while silver remains as a solid precipitate.
●The silver is extracted as a powder in this stage.
●Fumes from the reaction are handled by a scrubbing unit to neutralise emissions.

Step 2: Acid Neutralization

●The gold solution is transferred to a second reactor.
●Caustic soda and ethylene rings are used to neutralise the acids.
●The scrubber tower ensures that the fumes are neutralised safely, avoiding pollution.

Step 3: Gold Precipitation

●The neutralised solution is treated with sodium metabisulphmet astability.
●chemical reaction forms a gas, which precipitates pure gold from the liquid.
●The gold obtained at this stage has a purity of 99.99% and is collected in powder form.

Final Step: Obtaining the Refined Gold

●The gold powder is collected and processed for melting into bars or other forms.
●The final product is high-purity gold, ready for industrial use or resale.

Technical Features of Aqua Regia Refining Plant

The refining system is designed for high efficiency and safety, featuring:

✅ High-quality materials – The plant uses borosilicate tempered glass, PTFE, and PVDF for chemical resistance and durability.

✅ Automated operation – No physical handling of acids, reducing risks.

✅ Air-compressed cementation tanks – Helps in the refining process with adjustable pressure up to 5 BAR.

✅ Cooling and fume extraction systems – Uses normal water at 3.5 BAR pressure and a refrigerated water supply for safe operation.

✅ Capacity – The basic setup can refine up to 12 kg of gold per day using three reactors and two storage tanks.

Conclusion

The Aqua Regia gold refining process is a highly effective, safe, and economical method for obtaining high-purity gold. It is widely used in industries that require refined gold for further processing or sale. With advanced technology ensuring minimal environmental impact and operator safety, it remains one of the best choices for modern gold refining.

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