Refining of precious metals is carried out both in industry and by amateurs at home.
The goal of the event is to extract valuable raw materials by purifying them from foreign impurities.
Before moving on to the description of refining methods, equipment and reagents that are necessary for the process of recycling raw materials, let’s define the terminology.
What does gold refining mean in jewelry?
So, what is gold refining? This is the name of the metal cleaning process. Not external cleaning, when the product is restored to its former cleanliness and shine. Refining or refining is the removal of additional impurities from gold. This process can also be called refining. Refined gold, like sugar, is a perfectly purified element.
Refining of mined gold at a factory
For example, during mining it is difficult to find perfectly pure gold bars. Most often these are grains mixed with other rocks or just earth. It is also important to know that precious metals, such as gold and silver, are mined from the same ores. Therefore, they are always present in each other’s impurities.
The mined precious metal is processed at the plant, where it is refined.
The result is the production of refined gold - a metal of 999.9 purity.
Accordingly, the gold products used also have additional impurities – other metals. Therefore they need to be refined. So, from jewelry of 585 standard it is quite possible to get 999 standard.
Refined silver
To refining silver precious metal, electrolytic and chemical methods are used, as well as the cupellation method.
In apartment conditions, to obtain refined silver metal, it is possible to use only the chemical method. In this case, silver is released from the solution in the form of sulfate, which has a black color. If you add ammonium chloride or ordinary table salt to the solution, the metal can be obtained in the form of chloride. The resulting liquid substrate is settled until it is separated into cloudy and transparent fractions. The refined silver will need to be recovered from the sediment.
Raw materials for refining processing
To obtain refined gold, they work with certain raw materials. These are gold-containing materials:
- Natural mixtures containing precious metal. It can be minerals, rocks and even river sand.
- Scrap gold. Used gold items and elements. For example, jewelry scrap includes earrings, rings, chains, bracelets, pendants, and brooches. Technical – radio engineering waste, radio components, microcircuits. Household scrap - coins, dishes, watches, badges, medals. This also includes some types of bladed weapons (sabers, swords, daggers), souvenirs and antiques.
- Waste after purification of medical alloy. For example, gold plating applied by gilding.
- Lead production concentrates. Lead contains noble metals - gold and silver. To separate them, zinc is used. When heated, it forms a silvery foam, which picks up precious metals and is separated from the lead.
- Rough gold. This type of raw material makes up the largest share subject to refining. This is all the precious metal mined. It goes to processing plants, where it undergoes refining treatment.
Placer gold
As you can see, gold is not only a product of extraction in mines. Noble metal is present in the life of every person: in jewelry and household items.
Conclusion
Knowledge of refining methods, as well as the initial raw materials, which contain precious metals in one percentage or another, contributes to the profitability of VDM purification processes.
The main thing is to follow safety precautions and comply with the law when it comes to the subsequent sale of rare elements. In addition, in order not to lose money on gray schemes of shadow structures that meaningfully reduce the real cost of VYD, it is recommended to cooperate with organizations that have state licenses.
This also applies to “impatient” entrepreneurs who buy scrap containing precious metals from the population without subsequent refining. Donate all kinds of resistors, transistors, microcircuits, gold-plated watches, jewelry, etc. It would be more appropriate to join official structures.
Metal cleaning locations
Gold can be refined under special conditions. In what places is this procedure carried out?
Industrial cleaning in enterprises using electrolysis
Refining processing of precious metals is carried out by industrial enterprises specializing in this process. Gold is refined through electrolysis. This process involves passing raw materials through an electric current, as a result of which they are divided into parts. The noble metal is easy to separate from them. There are very few such enterprises. Russian enterprises: Uralelectromed, Krastsvetmet, Kolyma Refinery, Novosibirsk Refinery in Kazakhstan.
Metal cleaning by electrolysis
Equipped laboratories
If refining is carried out on a small scale, then specially equipped laboratories are suitable.
Where to deliver the received material and at what price?
The gold ingot (barrel) obtained as a result of purification most often has insignificant weight. However, even in such quantities it is of interest to buyers.
Advertisements for buying gold can be easily found on the Internet or in local newspapers.
Often, solid metal is purchased by the same companies that buy radio components.
(for example, aluminum or brass) may also be interested in gold
If the buyer is in the same city as the seller, the transaction is completed upon visiting the specified address.
The buyer himself weighs the metal and checks its quality, after which he sets a price. Of course, if possible, it is advisable to check all offers on the market in order to choose the most profitable one. The bullion can be sent to another city by mail, cash on delivery.
Some pawnshops are also ready to accept goods of this kind. To find out at what price the establishment will be willing to purchase gold, contact a pawnshop employee. Another option is to submit an ad yourself . In this case, you just have to wait for a call from a potential buyer.
If you engage in refining on an industrial scale, you should rely on existing laws.
To legally engage in the circulation of precious metals, you need to register as an individual entrepreneur or create an LLC.
When selling gold, focus on its purity and market value.
The price per gram of 999 fine precious metal is set by the Central Bank of Russia . Since 2004, its prices have been continuously rising. The most significant jump was observed in 2021, when the cost exceeded 3 thousand rubles per gram.
Refining methods
There are two ways to purify a precious metal or separate it from impurities:
- chemical;
- electrochemical.
The first method is associated with the interaction of substances, the second – with electric current. Let's consider each of the refining methods.
Chemical methods
There are methods that can be used at home. But some methods are only permissible in laboratories due to increased danger. For example, affinity is carried out using the strongest hydrazine hydrate reagent with the formula N2H4•H2O.
Let us list and analyze how the simplest chemical methods of refining are carried out.
Chemical solution for gold refining
Dry cleaning using the Miller method
This method of refining processing of precious metals is used only by industry, since the chlorine used in refining has a high level of toxicity and corrosivity. Actually, the method itself: all the raw materials are crushed, chlorine gas is passed through it. All base compounds combine with chlorine and evaporate. The fineness of the metal thereby increases. Among the advantages of the Miller method it is worth highlighting:
- low cost;
- use in small areas;
- short time: only a few hours;
- efficiency: you can get 999 gold from scrap.
To purify raw materials, a crucible is needed - this is a fire-resistant container. When gold-containing components begin to melt, chlorine enters the crucible through a special pipe, and then excess impurities are evaporated along with it, the chloride of the noble metal appears on the surface. This method makes it possible to refine gold even from alloys consisting of complex components.
Wet method with aqua regia
The wet method allows you to refine gold from the alloy by dissolving it with certain liquids. For example, one of the popular refining methods is dissolving scrap gold with aqua regia.
For reference: aqua regia is a mixture of concentrated acids: nitric and hydrochloric. By the way, aqua regia is a rare substance that dissolves the noble metal.
What does the refining process look like? The aqua regia, together with the metal and copper sulfate, is heated, resulting in the precipitation of gold. With the right process, the output is 999 pure metal.
Necessary materials
In order to clean native gold from impurities, it is necessary to prepare chemicals. Some are easy to get - in pharmacies or specialty stores, but others will have to be looked for. List of required ingredients:
pure borax,
- nitric and hydrochloric acid,
- zinc baking powder.
It is better to use pure pharmacy borax. Material with impurities will not be suitable, as it will contaminate the gold rather than purify it. You also need to prepare a concentrated 70% solution of nitric acid and 38% liquid hydrochloric substance. They are mixed with water to create a bleach that is used to clean metal.
Zinc is needed to prepare royal vodka or cyanide solution. Only in these liquids can gold be processed that is resistant to aggressive environments. Even low-grade metal is so strong that nitric acid does not corrode it. After all, a liquid can only react with other metals contained in the substance - silver, brass, copper. But their molecules are blocked by particles of pure gold, so the acid cannot react to them.
Therefore, to refining gold with zinc, it is necessary to loosen the entire metal alloy and move its molecules as far apart as possible. Then the acid can react with impurities and turn them into liquid. The substance is then washed and the pure gold is separated.
How to refining microcircuits at home
Despite the complexity of the refining procedure, you can carry it out at home yourself. You can refine both jewelry, household, and technical scrap, the same microcircuits that people usually throw away. The main thing is to create appropriate conditions, properly prepare raw materials and necessary equipment.
Necessary tools, materials and raw materials
What gold-containing parts can be used?
- transistors of the KT series 101, 103, 117, 603, 613;
- microcircuits from old televisions, tape recorders, radios;
- Soviet-made connectors;
- radio tubes containing not only gold, but also silver and platinum: from one lamp you can extract up to 16 grams of the purest precious metal;
- semiconductors, diodes, LEDs, zener diodes, thyristors, capacitors;
- computer parts: connectors, microcircuits in processors, there is a lot of special precious metal in old models;
- coating of Soviet-made metal wristwatches;
- SIM cards.
All this rubbish can lie somewhere in the attic or in the country for years, and the owner will not even suspect how rich he is in gold.
Gold-containing parts
What else is needed besides microcircuits?
- normal whiteness;
- sodium bisulfate.
Or:
- white;
- battery electrolyte;
- table salt.
By mixing these ingredients, you can get hypochlorous acid, which separates the precious metal from the components.
The procedure can also be carried out using iron sulfate. For this you need:
- iron sulfate: it is obtained by dissolving vitriol in water, and rusty nails are also added there;
- sodium chloride;
- hydrochloric acid.
Equipment
Various methods for cleaning VDM will require appropriate equipment.
We offer an approximate list of what will definitely be used:
- durable large tweezers, which will be needed for immersing pieces of raw materials into the molten substance and removing the elements of the VDM;
- for stirring you need a long, 2-, 3-mm thick metal knitting needle;
- laboratory flask with a volume of at least 500 ml, with heat-resistant characteristics;
- electric stove equipped with a closed spiral;
- crucibles – ceramic containers for melting VDM;
- a cap with a hole in the bottom, which is needed to cover the raw materials containing VDM during calcination in the crucible immediately before the melting procedure;
- porcelain dishes, chemical funnel, etc.
All of the equipment listed above can be purchased at specialized stores for jewelers.
You can read the following articles on the topic of refining various elements:
- Gold refining.
- Silver refining.
- Platinum refining.
- Palladium refining.
