Electrowinning, also called electroextraction, is the electrodeposition of metals from their ores The most common electrowon metals are lead, copper, gold, silver, zinc, aluminium, chromium, cobalt, manganese, and the rare-earth and alkali. Electro-refining is the preferred method as an electrolytic process for gold and other precious metals. The electro-refining process uses a. The residue from the silver-cells, together with crude gold bullion, is treated in cells having a chloride electrolyte. These produce fine gold and.

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They are bent over at the top, so that they can be hooked over the conductors crossing the top of the cells. This machine is located in the wash-room Fig.

Electrolytic processes for gold and other precious metals – Nutec

On account of these high charges on very base bullion, most of it is sent to private refineries, where the facilities for handling this grade of material are better, and the refining-charges are consequently less than at the mints.

The baskets are made of maple, and all the joints are dovetailed, so that there is no metal in their construction. It is desirable that the anodes should not carry more than about 7 per cent, of silver. It achieves high-efficiency od and silver extraction from leach and other pregnant solutions.

These gold strips are connected by screws alternately to the positive and negative busbars, and form the conductors. This electtrorefining electrolyte is treated in the scrap-copper tank to recover the silver, and then passes on to the scrap-iron tank, where the other metals contained if it are caught, as will be described under the head of Copper-Refining.

The sludge of cement-copper from this tank is washed and drained in wooden tubs with filter bottoms, whence it is transferred to other filter-tubs and allowed to air-dry, and then is melted down and cast into anodes for refining.

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The metal is melted in No. The test of the electrolyte for gold is made with ferrous ammonium sulphate. The granulated zinc is stirred into the mass of silver chloride and a little sulphuric acid is added to start the reaction. Silver — Gold — Copper. Gekko’s continuous electrowinning system allows minerals to be removed from the cell during operation. Electrolytic Processes for Gold and Other Precious Metals The electrolytic refining process for gold uses hydrochloric acid as the electrolyte.


This spongy material is crude or black gold with about 10 per cent, of silver and 1 per cent, of base metals. Electroforming process for Jewellery Industry: When in use, the rotor is lined with one thickness of 7-oz. They are 5 by 14 in. These tanks are shown against the wall in Fig. The cathodes are immersed 11 in.

High throughput, state-of-the-art electrowinning cells provide a low-cost option for silver producers, in particular, and leads to increased profits. There are 40 cathodes per cell and each has a normal immersion of 8.

Gold purity is typically These deeper cells will allow longer cathodes to be used, and, since wlectrorefining cores that have to be re-treated will be of the same size, there will be a reduction in the percentage of metal to be re-treated.

Anodes of gold fine are hung in strong hydrochloric acid, in five cells slightly larger than those used for the gold-refining process, and the cathodes, also of gold, are hung in porous cups filled with strong hydrochloric acid. However, they are not reusable and must be sent off for recycling. The crystalline metallic silver is deposited on these cathodes, and is removed at intervals with a long-handled dipper of hard rubber.

Electrorefining – Electrolytic Gold Recovery | Gold Refineries

The refinery takes the bullion purchased by the electrorefininh department, and carrying more than parts of precious metals in 1, or, in mint parlance, over fine, and separates and refines the various metals contained therein, using electrolytic processes exclusively. This gives, in the first cells, cathodes about The solution containing the base nitrates is treated as described under the head of Copper-Refining. The crystallized electrorefiing that collects on the cathodes is loose and is removed daily.


This precipitates the gold, which is allowed to settle by long standing. Many electroextraction systems are also available to remove toxic and sometimes valuable metals from industrial waste streams.

The spent electrolyte from both the vertical and the horizontal cells contains silver nitrate and the elecgrorefining nitrates of the base metals that were in the original bullion. These are then reduced by chemical reactions to refine the metal. The last two form chlorides and drop to the bottom of the cells as the anodes dissolve.

The rotors of the centrifugals are of earthenware and provided with ducts for the escape of the liquids. A second product of this process consists of the slime that accumulates in the bottom of the cells. When it reaches this condition, the gold-deposit on the cathodes is soft, and the electrolyte has to be changed.

The mixture is tested towards the end of the process for the presence of silver chloride, and when there is no longer any present, sufficient sulphuric acid is added to dissolve any zinc that remains. Second, the process permits the saving of all the platinum metals without serious inconvenience. James Elkington patented the commercial process in and opened the first successful plant in PembreyWales in Experience has shown that they are too shallow for advantageous work.

Each propeller, 2 in.

In addition, electrowinning produces a very clean silver product that is straightforward to smelt. These cells produce pure copper, and collect a residue containing lead, some gold and silver, and all the metals of the platinum group that were in the bullion.

All the products of the silver process can be dried sufficiently in the centrifugals, so that they can be transferred to the crucibles and melted. The pure silver collects in a crystalline condition on the cathodes, which are lifted out daily and cleaned over large porcelain jars.