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Recovering gold and precious metals

Find out about the process for recovering gold and precious metals from waste materials

Among its many activities, Orovilla is also specialised in the process of recovery, analysis and refining of precious metals obtained from waste materials and discarded jewellery.

This type of activity, carried out by the staff of Orovilla, involves scrupulous monitoring throughout the manufacturing process and meticulous care taken at every step of the process. Orovilla can recover and refine gold, platinum, palladium and many other precious metals from the goldsmith sector (scrap and discarded jewellery), but also from many other industrial sectors.
Orovilla can provide its customers with complete transparency in all the phases and manufacturing processes, plus the possibility of carrying out any type of direct checks during the material analysis step.
Orovilla precious metals are almost totally pure and guaranteed by suitable certifications.

But let’s take a closer look at all the steps featured in the recovery process and processing of precious metal waste, from jewellery or a wide variety of industrial sectors.

Analysis of gold and precious metals

The specific technical regulations, taken as a reference point, to analyse and determine the fineness of gold and silver, are those foreseen by the Regulation for the application of Italian Legislative Decree No. 251 of 1999 (ISO UNI EN 11426/2000). So, we oversee the meticulous work of the Orovilla analyst after recovering a batch of jewellery.

A sample weight of about 0.25 grams is taken from the recovered material that is first thoroughly analysed and weighed, and then wrapped in a thin sheet of lead together with the silver inquartation, in a ratio of 1 to 3. This process will allow the two metals to be perfectly separated at a later stage.
This material is then placed in a crucible and transferred into an oven at a temperature of 1150°, until all the metal has been melted. Then, you get a bead which when put through a rolling mill turns into a thin strip. This operation is essential so that the acid separation (i.e. nitric acid) can act more effectively.

The strip is then inserted inside a measuring flask, together with some chemical products which prevent the acid from overflowing and then, everything is brought to the boil. The boiling step must be repeated two or three times.

Once the analysis step has finished, you obtain a piece of gold, that will be transferred in a crucible, where it will be annealed at a temperature of 800°/1000°. At the end of this operation, the piece of pure gold obtained from this step of the process will be weighed again: a simple calculation of the ratio between the initial weight and the final weight, multiplied by one thousand, will provide the degree of purity of the sample examined.

Refining gold and precious metals

There are many different ways to carry out the process of refining, based on the fineness of the alloy; for degrees of fineness in excess of 700°/°°, acqua regia is then used. Let’s look closely at what exactly happens and what all the individual steps called for in this process are.
The rods are melted in a crucible and the metal obtained from the melting process is poured into a bath of water, where the metal solidifies in flakes that are then transferred to a large tank and dissolved with aqua regia (i.e. a mixture of hydrochloric acid and nitric acid in a ratio of 3:1). In the first step, the flakes are dissolved cold and then by heating; this phase lasts a total of about three hours.

Once completed, the liquid is allowed to cool and is then, filtered under vacuum and transferred into a tank where precipitation of the gold occurs by adding bisulphite. In this step, the forced suction is carried out under the hood to make it easier to remove the sulphur dioxide which develops when reducing the gold chloride.
The liquid part which is deposited on the bottom, together with the gold precipitate, is filtered under vacuum. The gold remaining on the filter is washed multiple times with hot and then, cold water. Then, with a fineness of 999.9 °/°°, melting is carried out to produce a cast bar.

The pure gold recovered by this process can then be placed on the market and the cycle restarts.

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PeroVia Pitagora, 11 - 20016, Pero (MI)
MM1 - fermata Molino Dorino
Riceve solo il martedí su appuntamento ed è obbligatorio fissare l'appuntamento e clicca QUI per proseguire.
orovilla@orovilla.com
MilanoVia Mazzini, 16 - 20123, Milano
MM1 - MM3 fermata Duomo
Tel: +39 02-8853-215
Lunedi - Venerdi SOLO su appuntamento 9:00-16-00 ed è obbligatorio fissare l'appuntamento e clicca QUI per proseguire.
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orovilla@orovilla.com