The various parameters for the cyanidation of the original concentrate and its treated product are as follows: NaCN concentration is 0.1%, CaO concentration is 0.01-0.02%, and liquid-solid ratio is 3:1. The CN type AM-2B resin was charged in an amount of 10% by weight of the sample for 24 hours. The fineness of the concentrate is 93~95%-0.044 mm.
Table 1 Effect of conditions for processing concentrates
From Table 1 that, in the case where the carbonaceous material is completely burned, gravity concentrate cyanidation calcined directly after firing the two, you can be guaranteed to obtain high metal recovery rate: 91.4 - 95.5% gold, Silver is 69.3~79.0%. However, the recovery rate obtained from the calcination of flotation concentrate is lower, the gold is 79.1%, and the silver is 19-24%.
This may be due to the fact that during the calcination of the flotation concentrate, a noble metal compound (a fine gold impregnated in iron oxide and a melt such as silver smelting sulfonate) which is difficult to be cyanated is formed.
Under certain conditions (HCI 18%, liquid-solid ratio = 4:1, temperature 80 ° C, time 2 hours), the calcination of the flotation concentrate after pretreatment with hydrochloric acid is carried out, and the recovery rate of the precious metal can be improved. This proves that the above speculation is correct.
It was also found in the test that during the calcination of the flotation concentrate, the optimum parameters required for maximizing the recovery of gold and silver by cyanidation in the calcine pretreated with hydrochloric acid are inconsistent. For example, the recovery of gold and silver is only 81.3% and 85% for the calcination of the calcined two stages.
However, since the acid consumption of the calcine treated with hydrochloric acid is too large, a part of gold and silver may enter the solution from the calcine, so that a process of recovering the precious metal from the solution must be added. Therefore, from the economic point of view, the method of treating with hydrochloric acid under industrial production conditions is very unreasonable.
The precious metal is recovered from the concentrate by an autoclave leaching process with a higher recovery rate than the roasting process.
Under these conditions, the treatment of flotation concentrates is more difficult than the selection of concentrates. Under the optimal conditions (the temperature is 180 °C for 1.5 hours), the gold recovery rate is 99.5% and 90% for the direct adsorption of cyanidation of the re-elected concentrate and flotation concentrate.
The recovery rate of silver obtained from the autoclaved leaching residue of the re-concentrated concentrate is the same as that of gold, which is 99.5%, so that the silver recovery rate in the autoclaved leaching residue of the flotation concentrate is only 88%. Therefore, the hot dip slag of the flotation concentrate must be pretreated with lime milk in order to remove the elemental sulfur that is formed during the autothermal oxidation process.
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