Study on Extraction of Gold and Copper from High Copper Gold Concentrate
China is rich in copper and gold ore, usually using flotation method to produce gold and copper concentrate and then smelting. The gold concentrate containing 1% to 6% of copper adopts the conventional roasting-acid immersion-cyanide process, and the recovery rate of copper and gold can reach very satisfactory results; but for copper-rich concentrates containing more than 10% copper, With this conventional process, the acid leaching rate is only about 93%, and the acid leaching residue still contains a large amount of copper. It will have two effects: first, low copper recovery rate and poor economic efficiency; second, copper is a harmful element that affects gold cyanide leaching. Its presence not only reduces the leaching rate of gold, but also greatly increases cyanide. Consumption. Therefore, this type of concentrate is basically used for the distribution of other smelters in the sale, which not only increases the loss of metal, but also increases the freight rate, and also causes a backlog of funds. In view of the above situation, the conventional process flow is improved, and a new process is proposed to meet the requirements of extracting gold and copper from high copper gold concentrate.
First, the experiment
(1) Experimental materials
The experimental raw materials are from the high-concentration copper-gold concentrate of a mine in Northeast China, with a particle size of -0.044mm accounting for 93.34%. Gold: 25.27g / t, silver 71.66g / t, the remaining components (%): Fe 37.2, Cu 12.51, S 28.62, Ca 1.07, Al 2.4, Mn 0.026, Si 6.61, Mg 0.13, As 0.02, Pb 0.022, Zn 0.12, other 11.272. More than 80% ore chalcopyrite, pyrite followed by (10% to 15%), again ceruloplasmin, pyrrhotite and the like.
(two) experimental process
The roasting experiment of copper-gold concentrate was carried out in an 8kW muffle furnace, with a platinum- rhodium thermocouple temperature measurement and a thyristor power supply temperature control. The acid leaching test was carried out in a glass reaction vessel placed in a constant temperature electric heating water bath, and stirred with a JJ-1 type precision electric mixer. The cyanide leaching is carried out on a cyanide roller bottle.
Second, the experimental results and discussion
(1) Calcination temperature experiment
The copper gold concentrate was placed in a corundum plate and baked in a muffle furnace at different temperatures for 2 h. The obtained calcine was subjected to acid leaching: an initial acid concentration of 3 g/L, a liquid-solid ratio of 4:1, an acid immersion time of 2 hours, and an acid immersion temperature of 80 °C. After washing the acid leaching residue, it is placed in a roller bottle and cyanated and leached at normal temperature. Leaching conditions: liquid-solid ratio L/S=2, pulp pH=10.5, NaCN dosage 8kg/t, leaching 36h. The experimental results are shown in Table 1.
Table 1 Results of different temperature roasting experiments 
It can be seen from Table 1 that the leaching rate of the copper leached at 600 °C is the highest, which indicates that at this temperature, the copper-containing gold concentrate has the best sulfation effect, and the ratio of soluble sulfate to easy-dip oxide is the highest. As the temperature increases, the sulfation ratio decreases. When the temperature reaches 650 ° C or higher, a large amount of copper ferrite is formed, causing a sharp drop in the leaching rate of copper.
It can be seen from Table 1 that the copper leaching cyanide leaching can obtain a higher gold recovery rate and is relatively stable, all of which are above 98.5%. The leaching rate at 600 ° C reached 99.03%, indicating that the gold in the calcine was easy to immersion gold after the copper gold concentrate was roasted.
The leaching rates of copper and gold were relatively high at 600 ° C, so the calcination temperature was selected to be 600 ° C.
(2) Calcination acid leaching experiment
It can be seen from Table 1 that the copper containing more than 1% of the acid leaching residue is high, and the copper content is high, so that when the leaching slag is immersed in gold, the NaCN is consumed excessively, and the recovery rate of copper is low. At the calcination temperature of 600 ° C, the leaching rate of copper was investigated by using a two-stage high acid leaching process for the calcination. Since the leaching rate of a period of acid leaching is about 93%, and it is relatively stable, the conditions of the second stage leaching are mainly investigated to increase the leaching rate of copper. A section of leaching conditions was fixed, and the effects of liquid-solid ratio, temperature, time and leaching acid concentration on the second leaching rate of copper were investigated. Through the above series of conditional experiments, the optimized conditions were as follows: one leaching condition: 3g/LH 2 SO 4 , L/S=4, T=80°C, t=90min; two-stage leaching conditions: 150g/LH 2 SO 4 , L / S = 2, T = 80 ° C, t = 90min, a comprehensive experiment, the experimental results show that under the optimized experimental conditions, the average leaching rate of copper is 98.22%.
In order to further increase the copper leaching rate, the process mineralogy analysis of the leaching residue was carried out. Microscopy and scanning electron microscopy showed that the copper in the leaching residue mainly exists in the form of residual copper sulfide. It is mainly a chalcopyrite partially encased in minerals such as pyrite and quartz before calcination. The oxidation is incomplete or not in the roasting process. Caused by oxidation. In industrial production, if the boiling roasting control is good, the copper recovery rate will increase again. Therefore, the key to improving the copper leaching rate is the roasting process, which ensures complete copper sulfation during the roasting process, avoiding local overheating and incomplete oxidation.
(3) Leaching of impurity ions such as iron, calcium and magnesium
During the leaching process, sulfuric acid not only leaches with copper minerals, but also sulfuric acid acts with alkaline gangue and iron in the ore. This is also an important factor affecting copper leaching rate, while iron ion leaching is for subsequent electricity. The accumulation process also has an effect, and the acid concentration is changed to examine the leaching of impurity ions such as iron, calcium and magnesium.
The liquid-solid ratio L/S=2:1, the leaching temperature was 80 °C, the leaching time was 90 min, and the leaching sulfuric acid concentration was changed to investigate the leaching of iron, calcium and magnesium. The experimental results are shown in Table 2.
Table 2 Effect of sulfuric acid concentration on leaching of Fe, Ca and Mg
It can be seen from Table 2 that as the sulfuric acid tries to increase, the leaching rate of Fe and Mg increases remarkably; the leaching rate of Ca decreases slightly, because the solubility of calcium sulfate decreases as the concentration of sulfuric acid increases, resulting in sulfuric acid. Calcium is deposited in the leaching residue. Under the optimized conditions, when the concentration of sulfuric acid is 150g/L, the concentration of iron ions in the solution is 18.75g/L. Since the concentration of iron required by the electrowinning process is less than 3g/L, it is only necessary to increase the neutralization and iron removal after the second stage leaching. Enter the copper extraction electrowinning section.
(4) Acid leaching cyanidation experiment
After the slag is shaken, it is placed in a cyanide roller bottle. Cyanide leaching at normal temperature, leaching L/S=2, pulp pH=10.5, adding NaCN, leaching for 36h, after leaching, filtering, washing and leaching residue, and drying. The cyanidation results are shown in Table 3.
Table 3 Effect of sodium cyanide dosage on leaching rate of Au and Ag
It can be seen from Table 3 that the leaching rate of gold is basically stable with the increase of the amount of cyanide. When the amount of sodium cyanide reaches 6kg/t, the leaching rate of gold reaches 99.14%; compared with the cyanidation experiment at the calcination temperature, calcination The reduction of copper in the acid leaching residue is beneficial to increase the recovery rate of gold. The leaching rate of silver gradually increases with the increase of the amount of cyanide, but the overall leaching rate is low. The results of process mineralogical analysis show that the proportion of each phase of silver in cyanide slag is (%): water soluble silver 0.01, silver chloride 0.04, silver oxide 0.37, metallic silver 0.56, silver sulfide 10.38, iron mineral coated silver 34.48 Other minerals (SiO 2 ) wrap silver 54.17. It can be seen that due to the presence of a large amount of iron oxide impurities and SiO 2 , the silver has a "wrapping" effect, and in the cyanidation leaching process, sufficient contact between CN - and Ag is hindered, so that this portion of silver is difficult to leach.
Third, the recommended process
Based on the above experimental results, it is recommended to use the principle flow of Figure 1 to treat high copper gold concentrate.
Figure 1 Process flow chart of gold and copper extraction from high copper and gold concentrate
Fourth, the conclusion
(1) When calcined at 600 °C, the copper-containing gold concentrate has the best sulfation effect, and the leaching rate of copper obtained by calcination is the highest; after the copper-gold concentrate is calcined, the gold in the calcine is easy-impregnated gold;
(2) Under the condition of two-stage acid leaching, one leaching control condition: 3g/LH 2 SO 4 , leaching slurry solid-solid ratio 4:1, leaching temperature 80°C, leaching time 90min; second-stage leaching control condition: 150g/LH 2 SO 4 , leaching slurry solid ratio 2:1, leaching temperature 80 ° C, leaching time 90 min, the average leaching rate of copper is 98.22%;
(3) The roasting process is the key to further increase the leaching rate of copper. Only when the roasting process ensures complete copper sulfation, avoiding local overheating and incomplete oxidation, can the copper leaching rate be further improved;
(4) The leaching rate of gold increases with the increase of the amount of cyanide, which is basically stable. When the amount of sodium cyanide reaches 6kg/t, the cyanidation rate is 36h, the leaching rate of gold reaches 99.14%; the leaching rate of silver follows cyanide. The increase in dosage is gradually increased, but the overall leaching rate is low;
(5) The reduction of copper in the acid leaching slag is beneficial to increase the recovery rate of gold and reduce the consumption of cyanide.
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