Recovery of gold from arsenic pyrite concentrate by cyanidation-carbon adsorption method (1)

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Bureau of Mines investigated using cyanide - carbon adsorption process of recovering iron ore concentrate arsenopyrite gold. A stirred leaching test was conducted on re-elected concentrates containing 21.8 ounces / ton of gold , 6.4 ounces / ton of silver , and 85%-35 mesh of fineness of grinding . The leaching results indicated that the recovery rates of gold and silver obtained after 96 hours of leaching were 96.9% and 90.7%, respectively . The recovery of gold and silver in the noble liquid is carried out by adsorption with granular activated carbon in a countercurrent system. The gold loading per ton of charcoal is 2,556 ounces. Silver is 502 ounces. So far, this load is higher than the actual amount.

Foreword:

One of the objectives of the Mines Bureau is to develop processes that increase the productivity and efficiency of the selection of precious metals, and that this process minimizes damage to the environment. The research goal reported in this paper is to investigate the feasibility of recovering gold from arsenic-containing pyrite concentrates by cyanide - carbon adsorption.

The treatment of arsenic gold ore is mainly determined by the state of gold in the ore. Gold co-existing with quartz veins in the presence of arsenopyrite and pyrite is usually present in high-grade deposits with a range of particle sizes and quantities (eg, gold deposits in the Madurot region of California). The ore of these deposits contains a wide range of natural gold, and these dispersed granular gold exists in an inclusive state and is embedded between the individual crystals of arsenopyrite and pyrite. Some gold may also be present in the sulfide in the state of a solid solution.

The most common methods for treating pyrite gold ore are re-election and flotation, using both methods to recover gold and sulfide as much as possible. For example, the amalgamation method - the arsenic pyrite concentrate is in contact with mercury to capture natural gold, then the mercury plate or the mercury plate is washed to obtain mercury and amalgam, and the amalgam is distilled to recover mercury and obtain sponge gold. The sponge gold fire method is then refined to obtain a Dolkin ingot. Mercury tailings often contain large amounts of residual gold, so these tailings are shipped to the smelter for further processing.

Another common method is to calcine an arsenopyrite concentrate under oxidative conditions and then cyanide the spent residue to recover the precious metal. This method produces a large amount of harmful arsenic oxide and sulfur dioxide dust, which is discharged into the air, and the influence of the carcinogenic potential of arsenic (arsenic trioxide) soot has made it difficult for the production unit to concentrate the arsenic pyrite concentrate. Sold to the smelter. In order to protect the health of factory work, in order to prevent widespread pollution, environmental protection agencies and employee safety and health agencies plan to issue new arsenic-containing standards (for the surrounding areas of smelters), which are likely to force smelting The plant stopped processing the production of arsenic pyrite concentrate. In the absence of perfect process conditions, despite the increase in gold prices and increased demand, it is also possible to abandon the treatment of some gold-bearing arsenopyrite deposits.

This paper describes a simple and effective cyanidation - carbon adsorption process for recovering gold and silver from flotation of arsenic pyrite concentrate . The process is mainly suitable for small enterprises. The main advantage of this treatment result is that it can recover gold quickly and efficiently, and granular activated carbon can effectively adsorb gold. Test procedures and results:

The arsenic pyrite shaker concentrate sample used in this paper was taken from a small plant in California. The analysis of the concentrate is as follows;

Ingredients

gold     Ounces / ton   21.8

silver     Ounces / ton   6.4

arsenic     %     3.7

iron     %     32.5

sulfur     %     24.0

Silica   %     15.0

Spectroscopic analysis showed that the concentrate also contained small amounts of aluminum ( 0.5% ), copper ( 0.02% ), magnesium ( 0.3% ), manganese ( 0.5% ), lead ( 0.2% ), nickel ( 0.2% ) and zinc ( 0.1%). ). Mineral testing by electron probe confirmed that the main phase of the concentrate is pyrite and arsenopyrite, and contains a small amount of pyrrhotite, chalcopyrite, iron oxide (hematite, limonite and magnet). Mine), silicate. According to the results observed by the mineral inspection and the results of the mercury-mixing test, the monomer gold in the concentrate accounts for two-thirds of the total gold, and the partial-coated gold particle size is 100-m . The remaining gold and arsenic pyrite coexist in an inclusive state, and a small portion is in a solid solution state.

In order to determine the distribution of precious metals, the arsenopyrite concentrate was subjected to wet screening, and the +65 mesh material was 59% . Gold and silver in a ratio of particle size is almost the same level. The data is shown in Table 1 .

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