Activated carbon adsorption and recovery of gold and silver from cyanide-containing beneficiation solution

Containing copper sulfide complex multi-metal ore, gold is an important resource of the former Soviet Union. The ore is preferentially flotation to produce gold and lead mixed concentrates containing gold. When floating from the mixed concentrate, 38% to 44% of lead.

Activated carbon adsorption, each batch of activated carbon 1 ~ 2t, added to a special tank, stirred with compressed air for 2h to obtain activated carbon suspension containing 70 ~ 120g / L of charcoal. The carbon suspension is automatically added to the lead flotation tailings in an amount of 300-350 g ∕t. When the slurry is concentrated, the gold-loaded carbon particles enter the bottom of the concentrator and enter the copper concentrate during flotation of copper.

According to the practice of the plant from 1972 to 1975, when 88g of activated carbon was consumed per ton of ore, the loss of gold in the overflow of the concentrator was 8.62%. In 1975, when 420 g of activated carbon was consumed per ton of ore, the loss of gold in the overflow fell to 1.86%. Practice has proved that the addition of activated carbon to the overflow of the tailings concentrator, the gold adsorption effect is actually the same as the above results.

Belousov Trask (Велоусовек) beneficiation plant tailings thickener overflow containing copper (mg / L) Au0.8 ~ 2 , Ag0.5 ~ 1.5, Cu300 ~ 460, Zn20 ~ 30, the total CN - 1500 ~ 2100 . An aqueous suspension of activated carbon was added to the solution at 1 g ∕L to carry out two successive countercurrent adsorptions. The recovery rate of gold was 96%, and the carbon loading was 1000 g ∕t. However, in the test, it was found that about 10% to 15% of the very fine carbon particles adsorbed by gold were lost with the solution during the second stage of adsorption.

In order to reduce the loss of gold in the second stage of adsorption, the sedimentation rate of the gold-loaded carbon should be increased. For this reason, the effect of addition of flocculants were investigated iron chloride, iron sulfate, copper sulfate, zinc sulfate, lead sulfate. Experiments have shown that the carbon deposition rate is the same after adding these flocculants (2~2.5m∕h), but in addition to the satisfactory results obtained by lead sulfate, the other will reduce the adsorption capacity of carbon (CuSO 4 is reduced by 50%, ZnSO 4 is reduced by 30%, and ferric sulfate and ferric chloride are reduced by 20% to 25%. When lead sulfate 1000 g ∕m 3 is added to the second stage liquid, the content of suspended solids such as carbon in the solution is lowered from 300 to 500 g/m 3 to 30 to 50 g/m 3 .

In order to strengthen the contact between the second carbon particles and the solution, and improve the adsorption recovery rate of gold and silver , the solution is supplied to the conical bottom of the tank in a tangential direction through a hydraulic stirrer, so that the solution is mixed with the suspended carbon in motion and is pumped. cycle. The mixed liquid is distributed through the central pipe and then from the branch pipe. The final mixture is discharged from the upper part into a thickener to separate the gold-loaded charcoal. After the process was applied to production in 1975, the recovery rate of gold increased by 2.9%.

The Surinovsk concentrator was the first plant in the former Soviet Union to recover gold, silver and non-ferrous metals from the cyanide solution overflowing from the concentrator using activated carbon and ion exchange resins. The overflow of the concentrator of the plant is about 400-600 m 3 per day, and the components contained are (mg∕L): Au0.7, Ag4.5, Cu400-500, Zn40-50, and total CN - 500-700. , suspended matter 100 ~ 200.

Gold and silver are recycled using КАЛ type activated carbon with strong adsorption capacity and selectivity. The gold adsorption capacity of this activated carbon is 5.2 mg/g. Because the gold-loaded carbon is easy to lose the mechanical loss of gold (the loss of 0.3-0.5k∕g of carbon containing 300g∕t per cubic meter of solution), the overflow solution is changed to the static inclusion of the filter. The carbon layer adsorbs gold. The recommended activated carbon particle size is -2 to +1 mm and -1 to +0.5 mm each accounted for 40%, and -0.5 + 0.2 mm accounted for 20%. The industrial test filter has a diameter of 3 m, a height of 5.44 m, a carbon charging of 5 t, and a carbon layer thickness of 2.4 m. After one month of testing, 4000m 3 of the whole liquid passed through the filter. After two sampling and sampling, the carbon content of the carbon particles was 1.56 and 2.49kg ∕t, respectively, and the silver content was 1.39 and 1.34kg ∕t, respectively. The loss of gold is 0.2 to 0.3 and 0.03 mg ∕L, respectively. After the method was used in the production of the concentrator, a filter was added in 1974 to recover the gold in series.

The solution of the noble metal was removed, and the copper and zinc cyanide complexes therein were recovered using an AW-17 ion exchange resin. Each exchanger is filled with resin 3.5t, the thickness is about 1m, the feed rate is 3~4m 3 ∕h per cubic meter of resin, and after 8~16h adsorption, the solution contains copper reduced to 2~10mg∕L, and the zinc is reduced. 0.6 to 2 mg ∕L. The copper and zinc recovery rates were 95% and 99%, respectively.

After removing the copper and zinc, the solution was electroformed with a graphite anode to obtain a deposit from the copper anode. The composition of the deposit depends on the feed component. Typical compositions of the cathode deposit are: Au 100-150 g ∕t, Ag 1000-1700 g ∕t, Cu 45%-80%, Zn 5%-15%, and Cd about 10 g/t. The waste liquid after the recovery of gold, silver, etc. from the electrowinning is returned for use.

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