Copper oxide acid leaching test

With the increasing depletion and easy dressing and smelting copper sulfide mineral resources, the use of copper oxide ore resources and more attention. The minerals contained in the copper oxide ore are complex and difficult to enhance the copper grade through beneficiation and enrichment. In this experiment, the copper oxide ore was leached with sulfuric acid, and the influence of various factors on the copper leaching rate was investigated.

   First, the test materials

The test raw material is a coarse-grained ore after crushing a copper ore in Yunnan, with a copper grade of 0.95%, belonging to a low-grade copper oxide ore. The copper minerals contained in the ore are mainly copper oxide minerals, most of which are malachite and chrysocolla, with a small amount of black copper, azurite and azurite; followed by copper sulfide minerals such as chalcopyrite , covellite, bornite and the like; other metal objects with a brown iron pyrite and magnetite; gangue minerals are quartz, dolomite and the like.

The results of chemical analysis of ore are shown in Table 1, and the results of chemical phase analysis are shown in Table 2.

Table 1 Analysis results of copper oxide ore elements

Table 2 Results of chemical phase analysis of copper oxide ore

    Second, test methods and reagents, instruments

The leaching test was carried out in a 1000 mL beaker and mechanically stirred. After the leachate was filtered, the acidity and the mass concentration of each element were analyzed. The leaching residue was washed with water (several times) and dried to analyze the copper mass fraction and calculate the copper leaching rate.

Test reagent: industrial concentrated sulfuric acid, 17.93mol / L; hydrochloric acid, analytically pure, 12.14mol / L.

Test equipment: JJ-1 high-power electric mixer, automatic temperature control device (maximum temperature 300 °C), electric furnace, electric thermostat dryer, SHB-IIIA circulating water multi-purpose vacuum pump, 1000mL suction filter bottle, funnel.

Analytical instrument: XRF-1800 X-ray fluorescence spectrometer, GGX-6 atomic absorption spectrophotometer, lightning magnetic pHB-4 pH meter.

    Third, the test results and discussion

(1) Conditional test

In the single factor condition test, the effects of ore particle size, liquid solid product mass ratio, leaching time, temperature, sulfuric acid mass concentration and activator dosage on copper leaching rate were investigated.

1. Effect of ore particle size on leaching

The ore is ground by a vibrating mill and sieved using a 100-mesh standard sieve. The mass concentration of sulfuric acid is 50 g/L, the mass ratio of liquid solid product is 4 L/kg, and the mixture is leached at room temperature for 1 h. The test results are shown in Figure 1.

Figure 1 Effect of ore particle size on copper leaching rate

The ore particle size has little effect on copper leaching. The leaching rate of copper after grinding is increased. When the ore particle size is -100 mesh, 80%, the copper leaching rate is 61%, and then the leaching rate of copper is not reduced. Improve again.

2, the effect of liquid solid product mass ratio on leaching

The ore particle size is -100 mesh, 80%, the sulfuric acid mass concentration is 50 g/L, and the mixture is leached at room temperature for 2 h. The effect of different liquid solid volume-mass ratio on copper leaching rate is shown in Figure 2.

Fig. 2 Effect of mass ratio of liquid solid product on copper leaching rate

The liquid solid mass ratio has little effect on the copper leaching rate, the liquid solid mass ratio increases to 4 L/kg, and the copper leaching rate is stable at about 61%.

3. Effect of leaching time on copper and iron leaching rate

The ore particle size - 100 mesh accounted for 80%, the sulfate sulfate t concentration was 50 g / L, the liquid solid product mass ratio was 4 L / kg, and the mixture was leached for 3 h at room temperature. The liquid sample was taken every 10 minutes for the first 2 hours, and the liquid sample was taken every 20 minutes for the first 1 hour. The test results are shown in Figure 3.

Figure 3 Effect of leaching time on copper and iron leaching rates

In the first 20 minutes of leaching, copper leaching was faster, the leaching rate reached 57.27%, and the leaching rate increased slowly. After leaching for 50 minutes, the copper leaching rate was stable at about 61%, and the leaching rate of iron increased with the leaching time.

4, the effect of temperature on leaching

Ore particle size - 100 mesh accounted for 80%, sulfuric acid mass concentration 50g / L, liquid solid product mass ratio of 4L / kg, with a fully automatic temperature control device to control the leaching temperature, stirring leaching for 1h. The result is shown in Figure 4.

Figure 4 Effect of temperature on copper and iron leaching rate

The leaching temperature is favorable for the leaching of copper and iron. At 80 °C, the copper leaching rate is 76.6%, the iron leaching rate is 9.3%, the copper leaching rate is increased by 15% compared with room temperature, and the iron leaching rate is increased compared with room temperature. It is nearly three times, which also increases the amount of sulfuric acid.

5. Effect of solution sulfuric acid concentration on copper leaching rate

The ore particle size is -100 mesh accounted for 80%, the liquid solid product mass ratio is 4L/kg, and the mixture is leached for 2 hours at room temperature. The effect of sulfuric acid mass concentration on copper leaching rate is shown in Fig. 5. At room temperature, when the mass concentration of sulfuric acid is 10 g/L, the copper leaching rate is only 40%, and the leachate pH is 4.9. Sulfuric acid deficiency is the main reason for the low copper leaching rate. When the concentration of sulfuric acid t in the solution is higher than 30 g/L, the leaching rate of copper is stabilized at about 60%.

Figure 5 Effect of sulfuric acid concentration on copper leaching rate

6. Effect of activator dosage on copper leaching rate

The ore particle size is -100 mesh accounted for 80%, the sulfuric acid mass concentration is 50g/L, the liquid solid product mass ratio is 4L/kg, and the mixture is leached for 1 hour at room temperature. The effect of the amount of activator on the copper leaching rate is shown in Fig. 6.

Figure 6 Effect of activator dosage on copper leaching rate

The addition of the activator can improve the leaching kinetics, and the copper leaching rate can be increased by 5% when the mass concentration is 5 g/L.

7. Sulfuric acid mass concentration and sulfuric acid consumption

The leaching was carried out in sulfuric acid solutions of different mass concentrations, and the amount of sulfuric acid consumed by leaching 1 t of metallic copper under the corresponding conditions was calculated according to the copper leaching rate. The results are shown in Fig. 7. At the same concentration of sulfuric acid, the acid consumption at 80 ° C is significantly higher than 20 ° C, the higher the concentration of sulfuric acid in the solution, the more sulfuric acid is consumed during leaching. From the economic point of view, it is sufficient to leaching at a normal temperature with 30 g/L of sulfuric acid. Under this condition, the consumption of sulfuric acid per ton of copper is 11 tons.

Figure 7 Diagram of solution acid concentration (1t metal copper) and acid consumption

(2) Comprehensive condition test

According to the above test results, the control liquid solid product mass ratio is 4L / kg, sulfuric acid mass concentration 30g / L, room temperature, ore particle size - 100 mesh accounted for 80%, activator mass concentration 5g / L, stirring leaching 50min. The comprehensive test results of the three groups are shown in Table 3. The results of the phase analysis of the copper leaching slag are shown in Table 4.

Table 3 Comprehensive condition test results

Table 4 Phase analysis of copper in leaching slag

  Fourth, the conclusion

(1) The ore is highly oxidized, and combined with copper oxide accounts for 28.5%. At normal temperature, only free copper oxide can be leached with sulfuric acid, and the copper leaching rate is 61%.

(2) At normal temperature, after the concentration of sulfuric acid is higher than 30g/L, increasing the amount of sulfuric acid has no effect on the leaching of copper, and the impurity elements are leached in a large amount, which increases the consumption of sulfuric acid.

(3) The ore particle size is -100 mesh, which accounts for 80%, and the particle size is reduced again, which has little effect on increasing copper leaching rate.

(4) The elevated temperature can destroy the combined copper oxide in the ore. When the temperature is raised to 80 °C, the copper leaching rate is increased to 76%, but the iron in the ore also enters the solution in a large amount, consuming a large amount of sulfuric acid.

(5) The addition of activator can increase the copper leaching rate by 5%.