Recover gold from anode mud

1. The source of anode mud and the significance of recovering gold from it
Copper, lead, nickel, zinc, antimony and other heavy non-ferrous metal ores often associated with a noble metal such as gold and silver. In the process of mineral processing , gold and silver are often accompanied by precious metals into the concentrate, which is the concentrate. Concentrate is the raw material for smelting. The smelting process is generally: fire smelting - electrolytic concentrate is the raw material for smelting. The smelting process is generally: fire smelting - electrolytic refining. In the process of pyrometallurgical smelting, precious metals such as gold and silver are almost all entered into the corresponding semi-finished products (such as refined copper, crude lead, etc.) with the main metals (copper, lead, nickel, zinc, antimony, etc.). In the semi-finished product electrolytic refining, the main metal product is obtained, and the precious metal such as gold and silver is separated from the main metal and almost all enters the anode slime. Therefore, all the precious metals such as gold and silver in the concentrate are substantially enriched in the anode slime. The gold content in the concentrate is generally a few grams per ton. Although it is not high, the total amount of gold is quite considerable for a smelter that smelts hundreds of tons or even thousands of tons of concentrate every day. It makes sense to recover the gold in the mud. At present, about a quarter of China's total gold production is recycled by heavy metals.
2. Principle of recovering gold from the anode The composition of the anode mud is very complicated. It contains not only precious metals such as gold and silver, but also other accompanying metals and rare elements. When selecting the method for extracting gold from the anode mud, factors such as the composition of the anode mud and the scale of production must be considered, so that the production process and production cycle are short, the equipment is simple, the gold recovery rate and other valuable components are comprehensively utilized. Environmental pollution is small.
The anode slime of a large smelter is usually disposed of in a special workshop, and the anode mud of a small smelter is centralized and disposed of by a specialized factory.
3. Recovery of gold from copper anode mud Gold is recovered from copper anode mud. In the past, direct smelting or direct ash blowing was used to recover only gold and silver. With the advancement of technology and the importance of comprehensive utilization of raw materials, in recent years The conventional method of treating anode mud at home and abroad is pyro-electrolysis.
The fire method-electrolysis method for treating copper anode mud is mainly divided into three steps:
(1) De- selenium removal before smelting. The purpose is to avoid the loss of gold caused by the formation of matte and a large amount of slag during the smelting of copper and selenium, and to avoid the entry of copper into the smelting alloy to reduce the quality of the alloy, and also to recover copper and selenium. Decoppering and de-selenization can be carried out separately or simultaneously, and it is generally convenient to carry out simultaneously.
De-selenium removal of copper has direct acid leaching, oxidative roasting - acid leaching, sulphation roasting - acid leaching and the like. Currently more popular is sulphation roasting-acid leaching. The sulphation roasting is to mix the anode slime with concentrated sulphuric acid into a small rotary kiln for the purpose of roasting the copper in the anode mud into soluble oxides and sulphates for leaching and simultaneously changing the selenium in the anode slime. The selenium dioxide volatilization furnace is recycled into the furnace gas. The acid leaching is to immerse the calcined anode mud (factory called calcine or kiln residue) with dilute sulfuric acid in the leaching tank, and dissolve the copper oxide and sulfate, and the copper is removed after solid-liquid separation.
(2) Leaching slag reduction and smelting. Compared with the anode mud, the leaching residue has a greatly reduced copper selenium content and can be smelted. The purpose of the smelting is to enrich the gold and silver in the anode mud to become a gold-silver alloy, in preparation for the next step of gold and silver separation.
There are two methods of smelting leaching slag and two-stage smelting. At present, the large-scale fire treatment of anode mud at home and abroad uses two-stage smelting. The so-called two-stage melting is to first smelt precious lead and then oxidize and refine. Lead smelting expensive, flux (e.g., soda, lime, quartz, fluorite, etc.) and a reducing agent (e.g., iron scrap and coke) adding an appropriate amount of lead and lead bullion is formed expensive (i.e., lead - silver alloy), other Most of the impurities enter the slag and soot. Oxidative refining of precious lead, also known as ash blowing, is essentially to blast the surface of the precious lead molten pool, and add oxidant to oxidize lead and other impurities into scum and separate from gold and silver to obtain gold and silver alloy containing more than 95% gold and silver. .
(3) Electrolytic refining and recovery of gold, that is, separation of gold and silver by electrolysis.
4. The method for the treatment of lead-anode sludge in the lead anode mud is generally determined by the amount of selenium and tellurium . When the lead anode slime does not contain selenium or antimony, it is only necessary to dry the anode mud, add soda and quartz in the reverberatory furnace, and blast the air to oxidize and smelt. The precious metal slag produced in the first place during smelting can be sent to the blast furnace for refining. When selenium telluride in lead anode slime needs to be recovered, a similar method to copper anode slime should be used.
5. Recovery of gold from nickel anode mud
Similar to copper, lead, and anode mud.

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