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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The electric current ionises the electrolyte and transfers dissolved gold from the anode to the cathode, thereby increasing the purity of the gold at the cathode. The electrolytic refining process for gold uses hydrochloric acid as the electrolyte. Because metal deposition rates are related to available surface area, maintaining properly working cathodes is important.
Electrolytic Refining: Silver – Gold – Copper
The electrolyte dissolves and retains the copper and other soluble base metals. The gold anodes are made exclusively from the gold from the silver-cells, which assays about thousandths gold, from to thousandths silver, and a small amount of base metals.
For refineries where the silver-bullion is the product of cupel-furnaces, and carries less than from 50 to 60 thousandths gold, and not more than from 10 to 20 thousandths base metal, there is no question as to the superiority of the horizontal process. The gold chloride solution obtained from these cells has a strength of from to g. The generators are driven by current obtained from a public power-line and furnish direct current of the required potential for the different operations. It is similar to the commercial process of copper-refining; but it is of special interest here, because the metals of the platinum group, taken into solution in the previous operations, have now accumulated in sufficient quantities to be recovered.
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Centrifugal Machines are used to separate the moisture from the different products of the refining process, and to wash them free from soluble matter. For aluminium, this is the only production process employed. Each cell contains 23 anodes and 24 cathodes, hanging in alternate rows, 2 in. The residue from the silver-cells, together with crude gold bullion, is treated in cells having a chloride electrolyte.
There are 40 cathodes per cell and each has a normal immersion of 8. The anodes are cast in open cast-iron molds, and are of the dimensions given in Fig. The anodes, hung by C-shaped hooks of pure gold from the conductors running across the top of the cells, are immersed 7.
It shows in the central background of Fig. High throughput, state-of-the-art electrowinning cells provide a low-cost option for silver producers, in particular, and leads to increased profits.
It is used to dry fine gold cathodes, and other gold-products, before charging them into the melting-pots.
Electrowinning | Gekko
The same amount of current at the same voltage is used in both sets of cells. Third, the losses are liable to be greater on account of having gold in solution in the electrolyte. This decomposition of the electrolyte seems to be due to the displacement of its gold by the copper dissolved from the anodes.
In the silver process at the San Francisco Mint, the initial treatment of the bullion is in vertical cells. It is desirable that the anodes should not carry more than about 7 per cent, of silver.
These produce fine gold and leave a residue containing silver chloride. At times, this precipitated silver has been dissolved in nitric acid to make silver nitrate for the electrolyte, but it is often impure, and a better electrolyte is obtained by dissolving pure silver; hence the practice is not common.
Electrolytic Refining: Silver – Gold – Copper
On passing a current of amperes at 25 volts through the cells, the anodes are dissolved, giving a solution of gold trichloride in the cells; but, owing to the porous cups, there is no gold deposited on the cathodes. This cloth shows as a white frill around the tops of these cells in Figs. The cathodes are immersed 11 in.
After washing in centrifugal machine No. An outline of the system is shown by the diagram, Fig. The current being amperes, the current-density is 90 amperes per square foot of cathode-surface. Experiments using electrorefining to process spent nuclear fuel have been carried out.
When all the silver has been precipitated, the ferric salt gives a red color. These conductors are gold strips bent into an inverted trough od, and fit the top of the porcelain cross-bars.
A new set of cells, 18 in. When the anodes are eaten down so that they barely hold together which takes about 48 hrthey are removed, all the loose spongy material is knocked off, and the hard cores that remain are treated in the horizontal cells, to be described later.
These do no harm until the solution becomes so strong that the purity of the silver deposited on the cathodes is affected, when it has to be changed.