Carbon-bearing gold ore is rare in nature and accounts for less than 2% of the world's gold reserves. However, when the ore contains carbonaceous materials, it can adsorb precious metals in the cyanidation solution, thereby increasing the loss of gold and silver in the tailings. Therefore, when treating carbonaceous gold ore, it is first necessary to determine the adsorption capacity of the carbonaceous material for gold. The amount of gold adsorbed by carbon during cyanidation depends not only on the adsorption capacity of the carbonaceous material, but also on the ore size and leaching time treated by the cyanidation process. Therefore, the gold grade in the cyanide tailings tends to increase with the fineness of the grinding fineness of the cyanide ore, because the finer the grinding particle size, the larger the active surface of the carbonaceous material. For example, when the leaching time is long, the grade of gold in the tailings increases due to the longer adsorption of gold by the carbonaceous material. Therefore, in determining the cyanidation conditions of carbonaceous gold ore, the optimum ore size and leaching time must be determined.
In order to improve the cyanidation index of carbonaceous gold ore, the following methods can be used:
1. Leaching with a high concentration of cyanide solution.
Second, the material is first treated with an agent that inhibits the adsorption capacity of the carbonaceous material, and then cyanidated.
You hormone Yellow P (amount of 1 kg / t, the material in an aqueous medium with stirring for 2 hours), cresylic acid (an amount 0.67 kg / t, treatment time 25 minutes) and kerosene, heavy oil, petroleum and turpentine (the amount of these agents 1 to 2 kg / ton, added to the grinding machine) can selectively adsorb on the surface of carbonaceous particles and form a fatty acid film, which can not only reduce the adsorption of carbon on gold, but also make the carbonaceous material have obvious hydrophobicity. As a result, the carbonaceous material often floats on the slurry surface of the concentrator or agitation tank and can be discharged with the overflow of the concentrator.
3. Cyanide is carried out in two or three stages, filtered in the middle of each stage of cyanidation, and the filter cake is made into a slurry with fresh cyanide solution.
4. Repeated intense washing of the cyanide tailings with a gold removal solution or a fresh cyanide solution. If the tailings contain a lot of gold that has been adsorbed, it can be washed with Na 2 S (0.2-0.15%) solution, alkali, thermal cyanide solution and concentrated cyanide solution.
5. Treatment of carbon-containing gold ore by adsorption-flotation method, that is, adding fine-grain activated carbon or ion exchange resin in the cyanidation process, and then using the flotation method to absorb gold, carbon or ion exchange resin and gold in the ore. The carbonaceous ingredients float together.
Six, carbon-containing gold ores and concentrates available diaryl dithiophosphate acid, A- hydroxynitrile, lactonitrile, cyano vinylidene cyanide peach organic acid leaching is OK, as the organic cyanide leaching for gold The rate is ten times higher than the commonly used inorganic cyanide.
Carbonaceous gold ore can also be treated by re-election and flotation, in addition to the cyanidation process. Prior to flotation cyanidation, coarse free gold can be recovered from the ore using a chute and a jig, and the re-elected concentrate is treated by amalgamation .
The main purpose of flotation is to obtain waste tailings. The carbonaceous material can be floated well only with a foaming agent (butanol, isoamyl alcohol, diethoxyethane, pine root oil). The material may be treated with an inhibitor (water glass, sodium tripolyphosphate, etc.) if necessary. The carbonaceous gold concentrate can be directly cyanated (in this case, measures should be taken to prevent the harmful effects of carbonaceous materials) or cyanide after the oxidative calcination to make the carbon content in the calcined less than 0.1%; sometimes it is sent directly to the smelting plant for smelting.
When the processing carbonaceous gold - arsenic sulfide ores, flotation can be used mixed (added terpineol, butyl xanthate, copper sulfate) is selected from carbon bearing gold - arsenic or concentrate by flotation from the priority order selecting containing Carbon gold concentrate and gold-arsenic concentrate, and the two concentrates are combined and treated. The carbon-containing gold-arsenic concentrate is usually subjected to oxidative roasting, and the subsequent calcination is carried out by cyanidation.
The oxidized roasting of carbon-containing gold-arsenic concentrate is better in two stages: the first stage of roasting is carried out under the condition of temperature of 500-600 ° C and insufficient air supply, so that the content of arsenic in the calcining is less than 1%. And at a temperature of 650 to 700 ° C and a sufficient amount of air to be supplied, the second stage of baking is performed to burn off the carbon and sulfur. In order to burn off the activated carbon, it is not only necessary to feed in excess air and a relatively high temperature, but it also takes a considerable amount of time. When calcination is carried out in a boiling roaster, the calcination process proceeds relatively quickly and thoroughly. In order to achieve self-generated roasting in a roaster, the sulphur content in the concentrate should be 22% to 24%.
Gold-plated gold ore is processed at the Ariston-Golde-Ma Yingz gold factory in Ghana. The plant has a processing capacity of 1,200 tons / day. Metallic minerals are mainly gold, arsenopyrite, pyrite, followed by a sphalerite, chalcopyrite, pyrrhotite. The gangue minerals are mainly quartz , followed by calcite , iron dolomite, rutile and carbonaceous schist (or carbonaceous phyllite). The ore contains 9-11 g/ton of gold and contains 1% of carbon. Some of the gold is wrapped in quartz in a free state, while the rest is symbiotic with pyrite and arsenopyrite. The plant adopts a combined process of re-election-flotation and flotation concentrate roasting-cyanide. The production process is shown in Figure 1. 
Figure 1 Addition of sodium Ariston-Golde-Ma Yingzi gold processing plant production process
The ore is broken up to -6 mm in two stages and then subjected to two stages of grinding (I stage grinding to 55% - 0.074 mm) to 65% - 0.074 mm. In the grinding and grading cycle, free gold is recovered by a chute, a shaker and a jig, and the gold recovery rate is about 60%. Then, the tailings are re-selected for flotation, the flotation concentrate is subjected to oxidative roasting, and the calcination is carried out for cyanidation. 30% gold was recovered during flotation and oxidation. The flotation concentrate contains a large amount of sulfide and carbonaceous shield in addition to 85 grams/ton of gold. The flotation concentrate is first concentrated, filtered and dried, and then oxidized and calcined in an Edwalds double-action roaster (the temperature at the discharge end of the furnace is 800 ° C). The calcine was cooled with a cylinder cooler and rinsed with water. The concentrated product was subjected to a first stage cyanidation leaching with a stirred leaching tank (NaCN concentration 0.08%, leaching time 24 hours). The slurry after the cyanidation leaching is filtered by a filter, and the gold-containing solution is sent to the sedimentation operation, and the filter cake is sent to the second stage for oxidative leaching (the leaching time is 72 hours). The two-stage leached gold-containing solution is fed to the clarification and sedimentation operations, while the cyanide tailings are discarded. The total gold recovery rate of the plant is 90%. The average gold content in the second stage cyanide tailings is 1 g/t (the gold grade in the flotation tailings is 0.7-0.8 g/t).
Canada recently published a study on carbon-bearing gold ore in the Markel mine in Andalo. It reports that the metal ore minerals are mainly amber gold, pyrite, rutile secondly, sphalerite, chalcopyrite, pyrrhotite, goethite, titanium, hematite, magnetite and Copper blue, etc.; gangue minerals are mainly quartz, followed by mica , chlorite, black graphite minerals, calcite, muscovite and feldspar . Gold exists in the amber gold state in the ore. Amber gold is a gold-silver alloy with a gold to silver ratio of 3:1. The ore contains 14.6 g/t of gold and contains 4.7 g/t of silver; 85% of amber gold is encased in pyrite and the remaining 15% is encased in gangue minerals. The amber gold particle size is generally between 1 and 60 mm, of which about 20% is -20 microns. The ore contains 3% carbon, of which 1% is graphite and other organic carbon, and 2% is carbonate (calcite and dolomite); most of the graphite is encapsulated in gangue minerals. Most of the pyrite exists in a free state and is densely symbiotic with amber gold in the ore.
The results indicate that: 1. Direct cyanide of ore (grinding fineness -0.074 mm, sodium cyanide dosage is 0.453, 0.907 and 1.360 kg / ton, cyanidation time is 48 hours), due to the adsorption of graphite minerals Therefore, the gold recovery rate does not exceed 47%; 2. Try to use a jig to remove graphite minerals from the ore before cyanidation, but the test results are unsatisfactory because the ore is coarsely ground (+0.59 mm). Graphite minerals cannot be removed; gold is lost to graphite minerals when finely ground (-0.15 mm); 3, ore is ground to -0.074 mm, and then 6% of slime (-50 microns or -25 microns) is removed therefrom. Not only gold is lost in the slime, but also most of the graphite mineral can not be removed; 4. After the ore is ground to -0.074 mm, methyl isobutylcarboxylic acid is added separately at a slurry pH of 8.1 (amount of 22.68 g / Tons) can remove 45% to 50% of graphite by graphite flotation. At this time, the yield of graphite concentrate is 3%, the concentration of graphite concentrate is 6.6 g/ton, and the loss of gold in graphite concentrate is 1.4%; , graphite flotation tailings (grinding fineness -0.074 mm) to carry out cyanidation (NaCN dosage 0. 68 kg / ton, CaO dosage 0.453 kg / ton, cyanidation time 48 hours), the total gold recovery rate was 81.3%; 6, the pentyl potassium xanthate (amount 272 g / ton) was added to the graphite flotation tail When the gold-pyrite ore flotation is carried out in the ore (grinding fineness -0.074 mm), the gold-pyrite concentrate yield is 16.2%, the gold content is 84.9%, and the total gold recovery rate is 94.1%. The final flotation tail The gold content of the ore is 0.8 g/ton, and the loss of gold in the final flotation tailings is 4.5%; 7. The gold-pyrite concentrate is re-milled to -0.043 mm and then cyanidation (NaCN dosage 0.68 kg/ton, CaO) When the dosage is 0.453 kg/ton and the cyanidation time is 48 hours, the total gold recovery is 85.1%, the cyanide tailings contain 8.1 g/ton, and the gold loss in the cyanide tailings is 9.0%. Gold-pyrite concentrate (re-grinded to -0.043 mm) by oxidative calcination (temperature 500 ° C, calcination time 1 hour) and cyanidation after friction grinding (NaCN dosage 0.068 kg / ton calcine, CaO dosage 0.453 In kg/ton of calcine, the cyanidation time is 48 hours, the total gold recovery is 93.6%, the cyanide tailings contain 0.6 g/ton, and the gold loss in cyanide tailings is 0.5%. It can be seen that when the gold-pyrite concentrate is calcined before cyanidation, the total gold recovery rate can be increased by 8.5%.
The recommended process for this research report is shown in Figure 2.
Figure 2 Test procedure for carbonaceous gold ore in the Markel mine, Canada
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