Precious Metal Recovery ( Video )

Precious Metal Recovery refers to the reclaiming of precious metals from specific scrap materials. Many precious metal recovery services employ state of the art refining techniques, for extracting metals such as gold, silver and platinum etc.

These processes can extract precious non-ferrous-metals from industrial scraps, wires tubes and dishoarded bars. Recovery services are used in a variety of industries including, aerospace, jewelry, medical and the semi-conductor and printed circuit board industries.

These services may also include reducing the metal lots to assaying bars for evaluation, by utilizing thermal processes. Metal refining capabilities can include, melting and thermal reduction through incineration.

Recovery refers to the separation of precious metals from noble-metalliferous materials, some of these materials may include catalysts such as electronic assemblies or printed circuit boards. 

To isolate or remove the metals, procedures such as hydrolysis or pyrolysis are commonly employed. With hydrolysis, the noble-metalliferous materials can be dissolved in hydrochloric acid and chlorine gas solution, or dissolved in Aqua regia, which consists of hydrochloric acid and nitric acid. 

In the procedure known as pyrolysis the precious metals are removed by solidifying in a melt to become cinder, and then oxidized. Some metals may be reduced directly with a gas or salt or nitro hydrate connection.

This is followed by various cleaning stages or are recrystallized, and the metals can then be separated from the salt by calcination. These precious metal materials are first hydrolyzed and then thermally prepared (pyrolysed) thereafter. The recycling product is removed and put several times through the cycle.

Precious metal recovery services are companies that purchase materials such as printed circuit boards, old wires, and industrial scraps that contain various precious metals such as :

o Gold & Silver

o Platinum

o Nickel & Tin

o Rhodium

o Palladium

o Copper & Bronze

These materials are then put through various processes to extract the precious metals from them. This makes good economical and environmental sense.

These services may also include buying old jewelry, and other valuable scrap metals such as :

o Brass

o Copper

o Bronze

o Aluminium

o Phosphor Bronze

These metals can then be smelted down and reused, thus saving valuable resources.

This is Video from Precious Metal Analysis - Instrumental Methods for Gold, Silver, Platinum, Palladium and other PGMs

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How Process Fire Assaying For Mineral (Video)

Fire assaying for mineral is the oldest and is considered to be the most reliable method of determining the content of gold and silver in rock or concentrate samples. This method is still the industry standard. The reason why it is called ”fire” assay is simply because it involves smelting the sample which has been mixed with lead oxide.

There are six basic steps in the fire assay procedure: 

• Splitting 
• weighing 
• mixing 
• firing 
• cupelling
• parting.

How the process fire assaying for Mineral

First, the crushed and ground sample of ore or concentrate is carefully split down to smaller samples only around 30 grams. These samples are weighed out and added to a crucible. A mixture of lead oxide, a reducing agent and fluxes is then added. The fluxes usually consist of silica sand, borax and sometimes additional additives like fluorite. The fluxes, reductant, lead oxide and sample are then mixed and fired in a muffle furnace.

The contents of the test material into the container then let all the ingredients to melt in the furnace smelting. In the presence of the reducing agent, typically carbon in any form, e.g. flour, the lead oxide is smelted to lead metal which “collects” any silver and gold that may have been in the sample.

The molten mass is taken from the furnace and mixed before being poured into a cone-shaped mold and allowed to cool. The molten lead sinks to the bottom of the mold, carrying any gold and silver with it, while the rest of the components of the ore along with the flux turn into a glassy slag that floats on top.

After cooling, the metallic lead at the bottom of the mold is separated from the glassy slag which is discarded. The lead is called a “button.”

This metallic lead button is then placed into a cupel, a small dish made from bone ash, and placed into a cupelling furnace. In the “cupelling” process, lead metal turns back into oxide which separates away from the precious metals and soaks into the bone ash cupel, leaving the minute amount of precious metals as a metallic speck called a “bead.”

The next step in the process is called parting, where the bead is weighed to determine the amount of gold and silver that was extractable from the original ore sample.

The bead is then heated in hot nitric acid which dissolves the silver, leaving any gold that may have been present. The parted bead is then carefully weighed and amount of gold is related back to the weight of ore or concentrate sample in the first crucible that was burned.

In more modern laboratories, the bead of precious metals that is recovered in the cupel after the lead has been removed is dissolved in aqua regia. The resulting solution is then analyzed by atomic absorption spectrometry, allowing the grade of gold and silver in the original sample to be back calculated.

Fire assaying is a science, and also to some extent is still an art. Certain types of ore contain elements that may interfere with the result. A good fire assayer knows how to modify the composition of the flux to avoid these problems. The fire assayer knows how to determine the gold and silver content of the assay ton of sample that has been presented.

Video Fire Assay Explained- The Workhorse of Precious Metal Analysis - Gold, Silver and PGMs

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