Gold Refining System

Gold refining is the process of purifying raw gold to make it usable for commercial and industrial purposes. Gold extracted from the natural environment often contains impurities, and these impurities mean that gold needs to be purified to different degrees depending on its intended use. Gold refining involves the process of converting gold into pure gold after it is extracted from nature through stages such as smelting, chemical processing and purification.

1. Gold Refining Methods

There are different techniques for gold refining and the methods used may vary depending on the purity of the gold, the type of impurities and the quantity to be refined. The most commonly used methods are the following:

a. Aqua Regia (King Water) Method

Aqua Regia is a mixture of acids that dissolves gold. This method is particularly favoured in medium-sized gold refining plants. Aqua Regia is a mixture of hydrochloric acid (HCl) and nitric acid (HNO₃). When gold is immersed in this mixture, it dissolves into gold chloride (AuCl₃). Subsequently, reducing agents (usually sodium metabisulphite) added to the solution precipitate the gold and purify it.

b. Electrolytic Refining

The electrolytic method uses electric current to obtain pure gold. In this method, gold is used as the anode and pure gold is deposited on the cathode. The impurities in the anode remain in the electrolyte solution and the process can produce gold with 99.99% purity. Electrolytic refining is widely favoured for industrial applications where high purity gold must be obtained.

c. Wohlwill Process

The Wohlwill process is a specialised version of electrolytic refining and can increase gold purity up to 99.999%. In this process, gold chloride electrolyte is used and the gold anode is dissolved in the solution and pure gold is deposited on the cathode. This method is often used for applications requiring high purity, such as electronics and precision devices.

d. Miller Process

The Miller process is a method in which chlorine gas is used to purify gold. Gold is melted and treated with chlorine gas. This process causes metallic impurities other than gold to be converted into chloride compounds, and these impurities are removed by rising to the surface of the molten gold. The Miller method is generally used to produce gold with a purity of 99.5%, but additional refining processes are applied when higher purity is required.

2. Refining Process Steps

The main stages of gold refining are as follows:

1. Raw Material Preparation: Raw gold is processed according to its purity and the type of impurities it contains. It is usually processed as ore or scrap gold.
2. Smelting: Raw gold is melted at high temperatures to liquefy the metal. In this process, impurities other than gold solidify and are separated from the liquid gold.
3. Chemical processing: Chemical reagents are used to dissolve the gold and remove impurities. The reagents used at this stage may vary depending on the method (e.g. Aqua Regia).
4. Precipitation of Pure Gold: Gold is purified from the solution by chemical methods and precipitated.
5. Final Purification: A final purification is carried out by electrolytic processes or other methods to increase the purity of the gold obtained.
6. Casting and Forming: The purified gold is made into ingots, bars or powder ready for commercial use.

3. Areas of Use and Importance

Gold refining provides pure gold that is used in different industries. The use of high purity gold is critical in areas such as jewellery, electronics, finance and medicine. Especially in electronic circuits and sensitive devices, gold's conductivity and corrosion resistance make it possible to produce quality products. In addition, gold bars are among the precious metals used in international trade and for investment purposes.

4. Environmental and Economic Impacts

The gold refining process can have environmental impacts as it requires high energy and chemical consumption. Environmental issues such as waste management, air and water pollution are an important factor in the sustainability of refining plants. Refining is also of great economic importance; high purity gold plays an important role in the global gold trade. Developing technologies and innovative processes enable steps to be taken to make the refining process more environmentally friendly and efficient.

Conclusion

The gold refining system makes it possible to obtain high purity gold by purifying the gold. Using different techniques and processes, gold is made suitable for industry and trade. This process, which has a great impact both environmentally and economically, will continue to be developed with more sustainable and efficient methods in the future.