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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You can follow any responses to this entry through the RSS 2. The rotors of the centrifugals are of earthenware and provided with ducts for the escape of the liquids. 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.
Posted in Further informations. The solution containing the base nitrates is treated as described under the head of Copper-Refining. The anodes are cast in open cast-iron molds, and are of the dimensions given in Fig. The gold chloride for the electrolyte is made by dissolving gold-bullion in hydrochloric acid by the aid of an electric current.
The test for silver chloride is made by treating a sample of the slime with ammonium hydrate, and then adding a few drops of hydrochloric acid to the clear solution. Gradually a firmer deposit collects that will not knock off, and this has to be removed with a scraper, when it comes away in sheets and leaves the cathode entirely clean.
This precipitates the gold, which is allowed to settle by long standing. The Current is a direct one of 15 volts, and eledtrorefining through the 18 cells in series, as shown in Fig. The gold process used at all the mints is the invention of Dr. Electrowinning offers a significantly higher efficiency of silver recovery with low operating costs, compared to zinc precipitation methods.
Most of the silver chloride, golld, drops to the bottom of the cells. All the metals in the anodes, including those of the platinum group, go into solution, except the silver and some lead. To prevent this, the bath is tested daily to determine its strength in gold, and if found to be low, is restored elctrorefining the desired standard by the addition of strong solution.
Electrolytic processes for gold and other precious metals – Nutec
The cathodes consist of graphite plates on the bottom of the cells. Electro-refining is the preferred method as an electrolytic process for gold and other precious metals.
The metal is deposited on the cathode either in solid or in liquid formwhile electrorefiniing anodic reaction is usually oxygen evolution.
The off occupies three large and three small rooms. Retrieved from ” https: It has generally been considered necessary to boil the crude gold from the silver-cells with concentrated sulphuric acid before casting it into anodes for the gold-cells, in order to reduce the silver to less that 7 per cent. It achieves high-efficiency gold and silver extraction from leach and other pregnant solutions.
This machine is located in the wash-room Fig. The slimes from the bottom of the cells, and the silver chloride that has been removed from the anodes, are washed free from soluble chlorides in glod machine No. This high-quality device permits greater process uptime, higher mineral yields, less washing and efficient cathode cleaning.
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They are considerably smaller than the cells, so that the deposited electrorefininh can be scraped and gathered from the cathodes through the space between a basket and the side of its cell. The cells are placed end to end in a double row on two long benches, 12 on one bench and 6 on the other. Skip to main content Skip to navigation. The test of the electrolyte for gold is made with ferrous ammonium sulphate.
Electrorefiningg engineered to handle the large volumes of high-value solutions, the electrowinning cell is well suited to enhancing silver recovery operations.
The metals of the platinum group also dissolve in the electrolyte; and while they occur in such small quantities in the bullion that they can hardly be detected, the quantity accumulated in the solution by the dissolving of many anodes is quite appreciable, and is recovered as described later, under Copper-Refining. These cells produce fine silver and leave a residue rich in electroreflning.
The operation in the horizontal od is the electroefining in principle as in the vertical, but the mechanical details are different. Alternatively, starter cathodes of pre-refined metal can be used, which become an integral part of the finished metal ready for rolling or further processing. This prevents the off solutions from settling to the bottom, and makes the deposition uniform over the whole cathode. There are 40 cathodes per cell and each has a normal immersion of 8. The English chemist Humphry Davy obtained sodium metal in elemental form for the first time electrorefininb by the electrolysis of molten ggold hydroxide.
In the silver process at the San Francisco Mint, the initial treatment of the bullion is in vertical cells. The large ones are, a melting-room, 30 by 34 ft. Electrolytic gold recovery begins with a bath of hydrochloric acid, which forms the electrolyte. Electrowinning High-efficiency silver recovery by electrowinning reduces operating costs and produces a superior product. The total amount of current is amperes.
These slimes are collected, washed with dilute sulphuric acid, dried, and melted into bars. The metal for the anodes is melted in the furnaces shown in Figs. The drive for the propellers is similar to that for the silver-cells. These show at the right-hand end of the first and second benches 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. They are suspended from the conductors by Electrorefiining hooks of gold, which pass through the hole at the top of the anodes and over bars which form the conductors for the current.