Non-roasting process for extracting gold and silver from refractory sulfide concentrates 1

For the gold-containing arsenic, pyrite concentrate dissociation of disseminated gold to cyanide Next, in recent years many new hydrometallurgical method. From the environmental point of view, it is reasonable to adopt these methods, but in addition to the process effects, these methods have many serious shortcomings. Mechanical crushing with planetary gear mills and jet mills is one of the promising processes in this area. In the ultra-fine grinding, the dissociation ability of the gold-containing sulfide minerals can be improved, and the decomposition of the gold mineral can be realized under the condition that the conditions are not strict, the chemical consumption is moderate, and the equipment shape is simple.

The raw material used in this test is one of the concentrates of Yakutia, and the concentrate is finely ground and then treated by hydrometallurgy. Use 56 grams / t Aa , 260 grams / ton Ag5.4% As , 16.8% S and 10.0% C concentrates were studied. Free gold does not exceed 6~8% , there is no natural silver .

Grinding is injected with MCII-05 and MCII-005 type mill. Using compressed air as the energy carrier, the gauge pressure is 0.45~0.50 _MIIa , consumption 80 meters ³ / hour. Approximately 100 kg of concentrate was processed under various grinding regimes . The material imbalance is 1.0~0.5% . The fine material is mainly lost with the bag filter exhaust gas.

The rotation speed of the classifier rotor is increased from 20 to 50 ^c ^-1 , the fine fraction yield can be increased: the content of -6+0 micron is increased from 45% to 87% . In this case, the string of -9+6 micron is reduced from 49% to 12%. , while medium-sized particles are reduced from 5 to 3.5 microns.

The sulfide minerals in the concentrates in the above-mentioned size range are characterized by high chemical activity (and Â The original mineral is 9-15 times higher than that of the original mineral , and it can be decomposed with sodium hydroxide solution at normal temperature and normal pressure. Under these conditions, mainly in the form of arsenate arsenic ions into the solution, and sulfur - in the form of sulfate and thiosulfate ions into solution. Under the optimal conditions, arsenic pyrite is decomposed by 80-85% and pyrite is -40~45% .

After mechanical crushing, the adsorption capacity of the pulverized mineral composite is increased.
In order to suppress secondary adsorption of Au and As , adsorption leaching must be carried out using an AM-26 type anion exchanger ( 8.05% ). The recovery of precious metals during cyanidation depends on the pre-alkali treatment time (Ï„)). If you increase this time from 12d to 48 hours,
In the case where other conditions are also ideal: liquid: solid = 6 : 1 , sodium oxygen oxide concentration is 50 grams / decimeter ³ , then the Au leaching rate will increase from 75% to 89.5% , and the silver leaching rate will increase from 81.5% to 96.6% . The cyanidation time is 48 hours, the liquid: solid = 4 : 1 , and the NaCN concentration is 0.4% , the cyanidation is more reasonable. The leaching kinetics curve of precious metals during concentrate cyanidation is shown in Figure 1 .
Recovery of gold and silver from concentrates treated in different ways
At Â Â Â Rational Â Â Â square Â Â Â law
Remaining content g / ton
Recovery rate %
Au
Ag
Au
Ag
Adsorption cyanidation of grinding ore concentrates, jet grinding concentrate, alkali leaching, cyanidation
12.50
76.00
77.30
91.30
-6 micron size, 90%
6.10
10.00
88.90
96.20
-15 micron size, 90%
5.80
8.00
89.50
97.00
Feeding ore size 70%-74 microns
17.60
100.00
68.00
62.50
As can be seen from the table, the index of adsorption cyanidation of concentrates depends on the pre-alkali treatment scheme. When the spray process is combined with the leaching of sodium hydroxide solution (according to Table 1 ), the highest recovery of the precious metal is ensured. At this time, the recovery rate of gold was 88.9% and silver was 96.2% . Jet milling adsorbed cyanide ore concentrates, in the absence of pre alkali leaching, Au recovery rate of not more than 77.3%, As 71.3%, the content of leaching residue were 12.15 and 76 grams / ton. When the treated product has a particle size of -6 microns and -15 microns, in fact, the same metric can be achieved. The above facts prove that it is possible to perform jet grinding with equipment used in production. The consumption of caustic soda is 85 kg / ton and cyanide 10 kg / ton.
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