Example of adsorption of gold from cyanide pulp by activated carbon

Homestake gold plant 1973 is stopped and switched to the use of mercury amalgamation CIP process it is as follows:

First, activated carbon adsorption gold.

The activated carbon used in the plant is -3.227 ~ +0.991mm (-6 ~ +16 mesh) coconut shell charcoal. After the cyanide slurry is stirred, the wood chips and the coarse ore are removed by a 0.701 mm (24 mesh) sieve, and then sent to the adsorption tank by an air lifter. The adsorption process consists of four air agitation tanks in series, each equipped with a 0.83 mm (20 mesh) vibrating screen. The carbon slurry is sieved by a vibrating sieve, and the slurry flows into the next adsorption tank, and the carbon particles on the sieve enter the previous adsorption tank, so that the carbon particles and the slurry are reversely moved. The final tailings of the fourth adsorption tank are discarded by a 0.701 mm (24 mesh) sieve to recover the ground carbon particles. The saturated gold-loaded carbon particles are sieved out from the first adsorption tank and sent to the desorption process once a day. The regenerated carbon particles (along with the new carbon) are added to the fourth adsorption tank. After four stages of series adsorption, the adsorption rate of gold and the saturation concentration of carbon particles are both high. When used to treat the slurry containing gold 154.1g∕t high grade ore, it has used 7-stage adsorption. The tailings pulp contains 0.035g ∕t of gold, and the recovery rate of gold is 99.98%. In general, it is sufficient to use level 4 adsorption. The residence time of the slurry in each adsorption section is 20 to 60 minutes, generally 30 minutes. The Homstek grade 4 adsorption feed slurry contains 1.92g ∕t of gold, and the tailings slurry contains gold of 0.015g ∕t. The adsorption recovery rate of gold is 99.2%.

Second, the desorption of gold-loaded charcoal.

The desorption operation was carried out in a conical stainless steel tank, and the adsorbed gold on the carbon particles was eluted using a hot (88 ° C) lye of 1% NaOH and 0.2% NaCN. The hot eluent flows through the two elution tanks in series from top to bottom, and the resulting eluate is sent to accumulate gold. This method is used to treat saturated carbon particles containing 9kg ∕t of gold, and the gold content can be reduced to 0.15kg ∕t after 50h.

Third, the electrolysis of the eluent is raised.

The electrowinning of the eluate was carried out in three FRP cells connected in series. A stainless steel plate for the anode and a graphite plate for the cathode. The electrolytic cell is divided into an anode chamber and a cathode chamber by a separator. The anolyte is a NaOH solution, and the eluent is supplied to the cathode chamber. Each chamber solution is circulated separately, and after the first tank catholyte is electrowinned through the second tank to the third tank, the discharged waste liquid contains almost no gold. This liquid is returned for desorption to reduce cyanide consumption.

The recovery rate of gold is greater than 90%. The processing fee per ton of ore is only $0.68.

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