Products & Solutions

Refinery

Precious Metal Recovery
„Urban Mining“ for the world of tomorrow

Our modern world is full of precious metals. No matter if power and information are transmitted in cars, household appliances, at the computer, in mobile phones or machines or whether a decorative surface for jewellery and dental use is to be achieved – precious metals are one of the most important resources of our economy.

Since their discovery thousands of years ago, they have fascinated us with their looks and abilities. Their limited natural appearance gives them permanent value. They have served as coin metal and asset protection since the early days. Today, they are valued particularly because of their high conductivity for electricity and heat, as well as for their resilience against oxidation. Our modern, digital life would be impossible without precious metals.

All products and assets are subject to a life cycle; they will be used up at some point or survived by progressing development. Precious metals are not. This is another benefit of the valuable metals: They can be regenerated as often as necessary. No matter in which function precious metals are used in products: it would be irresponsible and not economic to let them be lost in the waste. Even during the production of new products, precious-metal-containing wastes arise at regular intervals that are worth being recycled.

This is where the previous metal separation facilities, such as DODUCO from the Goldstadt Pforzheim (anniversary festival 2017: 250 years of Goldstadt) come in. Their main task is it to recover precious metals from production wastes and to save them from final loss. They therefore secure part of the raw material supply of the economy and form the basis for the future progress of technology. In particular in light of continually rising demands in the industry, and the barely rising production volumes, precious metal recycling helps essentially to fill the offer gap and to protect natural resources. In 2015, nearly 15% of the global silver offer and about 25% of the gold offer came from recycling.

The production and raising of the existing precious metals concealed in used products is therefore also called “Urban Mining”. The procedures used at DODUCO for previous metal recovery are much less destructive and efficient than the new production in mines. In 2015, DODUCO processed approx. 1,800 tons of precious-metal-containing production residues. Nearly 500 tons of silver were refined and returned to their pure form at 99,99% Thus, the traditional company from Pforzheim is one of the greatest silver processors in Europe and as an internationally certified processor and silver ingot provider listed on the “Good Delivery List” and an Associated Member of the LBMA (London Bullion Market Association).

The following pages contain more detailed explanations the different procedures of recovery of silver, gold, platinum, palladium and rhodium. Certain non-previous metal by-produces such as copper, tungsten or indium can also be recycled and returned to the economic cycle.

No matter the proceedings used for recycling: the target is always the same: Producing precious metals at the highest quality and purity. Gained from secondary raw material sources to protect nature and mankind. The conflict-freedom of refined gold has been confirmed to DODUCO by CFSI (Conflict-Free Sourcing Initiative) as well.

Precious metals are recovered from the following materials:

Contact Materials such as clad strip and stamping scrap, alloy scrap, Silver-Tungsten residues, brazed and assembled contact parts
Electronics such as micro processors, and ICs, ceramic substrates, paste coated foil scrap, connectors and switches, printed circuit boards
Electroplating: metallic scrap plated with precious metals, precious metal containing spent electrolytes and rinse waters, saturated resins and filters, electrolytically deposited precious metal powders and sludges
Catalysts from automotive exhaust systems or chemical processing, silver catalysts
Others such as jewelry alloys, jewelry making and dental alloy scrap

Features of a good precious metal separation facility

Everything from a single source: from the offer to processing to settlement

In addition to precious metals, trust is the most important resource with which a precious metal separation facility works. The customer, who brings his valuable wastes to be recycled, must be certain that his partner will treat them carefully and that he will receive complete compensation for all precious metals contained in the end. Perfect and comprehensive service also characterise a good and reliable separation facility.

What you can expect from us:

In advance

Quick request processing

Test separations and verifications of economic efficiency

Detailed and well-structured offers

After delivery

Immediate submission of the inbound order data

Schedule compliance and flexibility

Transparent settlement system with the cost components broken down into the individual process steps

Selection of compensation options for the precious metals produced

See in Wald mit Wald- und Hügellandschaft

Environmental awareness

The reclaiming and extraction of already existing precious metal treasures from used products is also termed “urban mining”. The processes used at DODUCO for precious metal recovery are significantly more efficient and conserving than new extraction in mines. In 2017, around 1.800 tons of production residues containing precious metals were processed at DODUCO. Looking at silver alone, almost 500 tons were refined and converted again into a 99.99% pure form. Consequently, the long-established company from Pforzheim is one of the largest silver processors in Europe and is included in the “Good Delivery List” as an internationally-certified refinery and a producer of silver bullion, as well as being an associated member of the LBMA (London Bullion Market Association).

Preperation processes

Prepartion-
processes

Technically, there are various methods of recovering silver, gold, platinum, palladium and rhodium. Also, certain base metals, e.g. Copper, tungsten or indium can be recycled and returned to the economic cycle.

But regardless of which recycling processes are used, the target is always the same: precious metals of the highest quality and purity. Obtained from secondary sources to protect nature and man. DODUCO constantly confirms the lack of conflicting sophistication of the gold through RMI (formerly CFSI – Conflict-Free Sourcing Initiative).

Electrolytically deposited

Many precious-metal-containing wastes from the industry are built based on other metals and their alloys. Copper is particularly important here. As pure copper, bronze, brass or other alloys, it forms the basis for many contact materials. The galvanically or massively applied precious metals ensure maximum conductivity and longevity. Many of such wastes in the form of punched parts, straps, rivets, etc. arise directly at production in the form of production residues or come from recycled electrical drives. DODUCO processes such precious-metal-containing residual materials on copper basis by melting subsequent electrolysis procedures in order to recover the contained silver, gold, copper or platinum metals.

Initially, it is important to weight the inbound fraction precisely. This net weight forms the basis for melt planning and later settlement. In the first process step, the material to be separated is now melted in a furnace. Depending on the amount of the individual delivered lots, this is done in one passage or spread out across several batches. Induction furnaces keep the material in motion continually while melting to produce a homogeneous mass. The even distribution of all elements contained in the material is very important for later analysis.

When the intended melting temperature has been reached, and the melted mass sufficiently mixed, the second step is taking a representative sample. A ladle is used to remove a small part of the liquid melt and cast it into a test ingot. This test ingot is marked clearly according to the batch and supplied to the analytic lab of DODUCO for analysis. The test ingot is cut across the entire cross-section in several locations to determine the specific contents of precious and non-precious elements, and the resulting sample chips are mixed and divided according to the a specified pattern. Then the actual analysis takes place using various methods (see the corresponding tabs).

Possible contaminations in the material are bound at the surface of the liquid melt in the form of slag and siphoned off. Subsequently, the material will be cast into bars or granules. The analysis values gained in the lab and the determined total weight after melting can be used to determine the precise content in silver, gold, platinum, palladium, rhodium and/or copper in the material to be separated. Transparent settlement with the customer is possible based on this.

After settlement, the actual refining of the metals contained will commence. First, different fractions of the material to be separated will be combined into roughly equally sized melting batches with specified silver contents. This combination of various items with different fine metal contents into a large melt batch is called “alloying”. The specified silver content to be achieved in the finished melt batch is necessary for an optimal effect of electrolysis later.

The prepared alloyed batches are melted in the furnace again and cast into anodes by continuous casting. Copper electrolysis now forms the next process step. For this, the anodes are suspended in an electrolysis tub; with thin copper sheets acting as cathode. The applied electrical voltage will cause the pure copper to separate at the cathode, while all other elements contained in the anode will settle on the bottom of the tub as sludge. The resulting sludge already contains more than 90% silver and is cast into smaller anodes after being melted again. These are now sent to silver electrolysis. During this process, the silver will be refined into a purity of 99.99.

All other precious metals that were contained in the original material to be separated will settle as sludge in the silver electrolyse. This is then processed chemically to separate the remaining precious metals.

Chemically precipitated

AgW, AgNi, galvanic baths, precious-metal-coated steels, processors, etc. cannot be homogenised by melting. These materials for separation as well as materials with valuable by-product elements (e.g. indium) will be processed chemically.

The precious metals are dissolved, e.g., with nitric acid or aqua regia and recovered in their pure forms by the classical separation steps (precipitation, filtration, washing).

Atomized

“Residues” are waste materials made up of mostly organic materials that include some precious-metal-containing components (paper, cleaning wool, plastic substrates, varnished materials). After burning in the residues ashing system, the resulting ash enriched in metal is either chemically processed or melted.

Mr. Armin Nittel
Sales Director – Refinery

Tel.: + 49 (0) 7231 602-482
Mail: anittel@doduco.net

Products & Solutions

Precious Metal Recovery
„Urban Mining“ for the world of tomorrow

Features of a good precious metal separation facility

Everything from a single source: from the offer to processing to settlement