June 02, 2020

Recovery of gold from arsenopyrite concentrate by cyanidation-carbon adsorption method (3)

Treatment of cyanide precious liquid by carbon adsorption:

use 4600 g Shaker concentrate and calcium oxide ( 20 pounds / ton) mix, join 10 pounds / ton of sodium cyanide solution 13.8 liters Stirring and leaching, and obtained 10 liters Containing gold cyanide solution, this 10 liters The solution was subjected to carbon adsorption studies. The storage time was 24 hours, and the slurry was precipitated until the supernatant solution was clear. The supernatant is then siphoned out of the slurry without any clarification. Determination of gold content per ton of noble liquid 310ppm , silver 57ppm , pH of 10.7 , free sodium cyanide 2.4 pounds / ton, also contains a large amount of sulfide and sulfate sulfur and a small amount of copper and iron impurities. Table 4 indicates the results of the analysis of the noble liquid. Since the precious liquid contains a large amount of spargent ions ( 320 ppm ), we call it "contaminated noble liquid".

(Actually metallurgists a "pollution" that is specified in expressions: cyanide leachate contamination of other components to be replaced with those of the interfering cyanide or zinc powder).

Other researchers have thoroughly studied the effects of harmful substances on cyanidation, such as sulfide ions, which seriously interfere with the recovery of zinc powder replacement. Sulfide ions at a concentration of parts per million can significantly impede gold displacement, and when the sulfide is 14.4 ppm , the precipitation of gold is completely stopped. The mechanism for the unfavorable results caused by sulfide ions has not been determined, but it is believed that the reason is that zinc sulfide encapsulates zinc metal.

The study uses activated carbon to recover gold and silver from the noble liquid because the carbon has a function of not being damaged in the contaminated cyanide solution. A gold tracer ( Au195 ) was added to the gold-silver containing solution to determine the degree of adsorption. This noble liquid with "trace" is pumped to five adsorption columns in series. The adsorption column is 1 inch in diameter and 4 inches high . Each column is equipped with 14.6 grams -6 mesh +16 mesh coconut shell activated carbon. Flow rate is 1 liter / hour or 48.5 gallons / hour · feet 2 . Figure 1 depicts the adsorption equipment used in the laboratory. Carbon in a carbon column - Analysis of the content of precious metal lean solution, and trapped when measured per liter using a radioactive effluent. The fire gold method was used to analyze the gold-loaded charcoal. The results are shown in Table 5 . Analysis of the difference between the loaded carbon and radioactivity measured by each load increment indicates a; when all the liquid is consumed expensive, - of a carbon carbon adsorption column can still gold. The data shows that if the precious liquid is added properly, the gold loading in the first carbon column is significantly exceeded. 2556 ounces / ton.

 

Table 5   Activated carbon with gold and silver results

Carbon load adsorption of gold and silver

Adsorption column

gold

silver

1

2556

502

2

1648

529

3

841

517

4

96

388

5

6

278

Preliminary studies have shown that granular activated carbon can effectively adsorb gold cyanide complexes from noble liquid contaminated by sulfide ions. Loading a first column 2556 carbon oz / t, which ratio is generally 200 to 800 ounces heap leaching is much higher production obtained. The reason may be that the gold content of the solution is 30 to 100 times higher than that of the noble liquid obtained by conventional treatment of the ore . The lean liquid obtained in the whole experiment contained less than 0.1 ppm of gold , and silver was also adsorbed, but not as effective as gold. The carbon loading of the charcoal is 500 ounces / ton. At the beginning of the adsorption test, there was no significant breakthrough in silver. But when it is processed 4 liters After the precious liquid, traces of silver were found in the lean liquid. In the final lean liquid volume, the silver content gradually increased to 19.5 ppm .

Conclusion:

Treatment of arsenic pyrite concentrate by conventional cyanide - carbon adsorption method can recover 97% of gold and 91% of silver in concentrate . It can be stirred and cyanated in the process of treating this material. However, air must be added to the diafiltration method to provide sufficient oxygen to ensure efficient dissolution. The recovery of gold and silver from contaminated precious liquid by carbon adsorption has been very successful. Available per ton of carbon 2556 ounces And silver 502 ounces . These loads are much higher than those obtained by conventional heap leaching because the amount of precious metals fed into the solution is 30 to 100 times higher.

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