Recovery of bismuth from copper anode mud slag

As a kind of rare element, 碲 is more and more widely used. Less independent tellurium deposit in nature, often accompanied by tellurium was born in copper, lead, bismuth ores, to be enriched in the by-product of the smelting of these metals, people have attached great importance to the separation of these by-product from the extraction of tellurium in. The copper electrolysis anode mud of a copper smelting plant in China contains 碲4.9%~9.3%, and the content of strontium in the alkali leaching residue, purification slag and strontium electrolysis anode mud produced during the extraction process of strontium is different, and the composition is complex. It is difficult to recycle. In this study, oxidized acid leaching method was adopted to extract cerium from these slag and mud mixtures, and good results were obtained.

First, the test materials

The raw materials used in this test are the mixed slag of alkali leaching residue, purification slag and strontium electrowinning anode mud produced during the recovery of copper slag from a copper smelter. The main chemical composition is shown in Table 1.

Table 1 Main chemical components of raw materials (%)

Second, the test method

Take a certain amount of sulfuric acid into a 1L reaction flask, heat it to a certain temperature on a water bath, add 50g of mixed slag and a certain amount of oxidant, after reaching the predetermined reaction time, sample and analyze the concentration of cerium in the leaching solution by atomic absorption spectrophotometer. , calculate the leaching rate of cockroaches.

Third, the test results and discussion

(1) Conventional acid leaching

Under the conditions of a leaching temperature of 80 ° C, a sulfuric acid concentration of 0.5 mol/L, and a liquid-solid mass ratio of 5:1, 50 g of the material was directly leached with H ₂ SO ₄ , and the results are shown in FIG. 1 .

It can be seen from Fig. 1 that the leaching rate of bismuth and copper increases with the leaching time, but the leaching rate of copper is higher, up to 85.85%, while the leaching rate of bismuth is lower, the highest is only 43.91%. Direct acid leaching without oxidizing agent, the hydrazine in the mixed slag cannot be completely dissolved. Therefore, the following test uses an oxidizing acid leaching method.

(2) Oxidizing acid leaching

1, the choice of oxidant

Under the conditions of leaching temperature of 80 ° C, sulfuric acid concentration of 3.6 mol / L, liquid-solid mass ratio of 5:1, and leaching time of 5 h, Fe ₂ (SO ₄ ) ₃ , KMnO ₄ , H ₂ O ₂ and The air was oxidized to oxidize acid leaching of 50 g of the material, and the effect of the oxidant species on the leaching rate of the hydrazine was investigated. In the test, Fe ₂ (SO ₄ ) ₃ and KMnO _{4 were} added in an amount of 10 g, H ₂ O _{2 was} added in an amount of 10 mL, and an air flow rate was 10 L/min. The test results are shown in Figure 2.

â—†-air; â– -Fe ₂ (SO ₄ ) ₃ ; â–²-H ₂ O ₂ ; â–¡-KMnO ₄

It can be seen from Fig. 2 that different oxidizing agents have different leaching rates of cerium. When air is used as the oxidant, the leaching rate of bismuth can only reach 54.91%; when Fe ₂ (SO ₄ ) ₃ and H ₂ O _{2 are} used as oxidants, the leaching rate of bismuth is also low, but the highest is 65.59%. Therefore, the above three substances are not suitable as the oxidizing agent for the oxidative leaching of the cerium mixed slag. When KMnO ₄ with stronger oxidization is used, the leaching rate of cerium increases sharply, which can be as high as 90.75%, indicating that KMnO ₄ is an effective oxidant for acid leaching of cerium mixed slag. Based on the results of this test, it was determined that the oxidant used in the subsequent test was KMnO ₄ .

2. Effect of KMnO ₄ dosage on leaching rate of hydrazine

Under the conditions of leaching temperature of 80 ° C, sulfuric acid concentration of 3.6 mol / L, liquid-solid mass ratio of 5:1, leaching time of 5 h, the amount of KMnO _{4 was} changed to oxidize acid leaching of 50 g of material, and the leaching rate of hydrazine was changed. Figure 3 shows.

It can be seen from Fig. 3 that as the amount of KMnO ₄ increases, the leaching rate of cerium increases rapidly first and then decreases slowly. When the amount of KMnO ₄ added is 0.4 g, the leaching rate of cerium reaches a maximum of 91.7%. It was thus determined that the oxidizing agent KMnO ₄ was used in an amount of 0.4 g for 50 g of the material.

3. Effect of sulfuric acid concentration on leaching rate of hydrazine

Under the conditions of leaching temperature of 80 ° C, liquid-solid mass ratio of 5:1, KMnO ₄ dosage of 0.4 g, and leaching time of 5 h, the sulfuric acid concentration was changed to oxidize acid leaching of 50 g of material, and the leaching rate of bismuth was as shown in Fig. 4. Shown.

It can be seen from Fig. 4 that as the concentration of sulfuric acid increases, the leaching rate of lanthanum gradually increases. When the concentration of sulfuric acid increases from 0.9 mol/L to 3.6 mol/L, the leaching rate of lanthanum increases from 83.71% to 91.7%, but when sulphuric acid When the concentration was further increased to 4.5 mol/L, the leaching rate of cerium increased only by 0.4% to 92.1%, and the excessive concentration of sulfuric acid was unfavorable for the subsequent process, so the selected sulfuric acid concentration was 3.6 mol/L.

4, the impact of leaching time on the leaching rate of cockroaches

Under the conditions of leaching temperature of 80 ° C, sulfuric acid concentration of 3.6 mol / L, liquid-solid mass ratio of 5:1, and KMnO ₄ dosage of 0.4 g, the leaching time was changed to oxidize acid leaching of 50 g of material, and the leaching rate of bismuth was changed. Figure 5 shows.

As can be seen from Fig. 5, as the leaching time is prolonged, the leaching rate of ruthenium is increased. When the leaching time is 5 hours, the leaching rate of ruthenium reaches 91.7%, and then the leaching time is extended without a large influence on the leaching rate of ruthenium. Therefore, the leaching time was chosen to be 5h.

5. Effect of leaching temperature on leaching rate of hydrazine

Under the condition of sulfuric acid concentration of 3.6mol/L, liquid-solid mass ratio of 5:1, KMnO ₄ dosage of 0.4g and leaching time of 5h, the leaching temperature was changed to oxidize acid leaching of 50g material, and the leaching rate of bismuth was as shown in the figure. 5 is shown.

It can be seen from Fig. 6 that when the leaching temperature is raised from 40 ° C to 80 ° C, the leaching rate of ruthenium is increased from 55.0% to 91.7%, and the temperature is continuously increased to 90 ° C, and the leaching rate of ruthenium is only increased to 92.1%. Therefore, the leaching temperature was selected to be 80 °C.

(3) Expanding the test

Through the above tests, it is determined that the suitable conditions for oxidizing acid leaching of cerium mixed slag are leaching temperature 80 ° C, liquid-solid mass ratio 5:1, KMnO ₄ dosage 0.008 g/g (for raw materials), sulfuric acid concentration 3.6 mol/L, leaching time 5h. Under this condition, 500 g of the material was subjected to an expanded oxidation acid leaching test, and the results are shown in Table 2.

Table 2 Oxidation acid leaching expansion test results

It can be seen from Table 2 that under the determined suitable leaching conditions, the leaching rate of the expanded test enamel reaches 90.09%, which proves that the oxidized acid leaching method can effectively leach the ruthenium in the ruthenium mixed slag, and at the same time, 97.81% of the copper can be leached.

Fourth, the conclusion

By oxidation acid leaching of a copper smelting can be effectively leaching copper anode slime integrated ironworks slag tellurium. The leaching rate of bismuth at a leaching temperature of 80 ° C, a liquid-solid mass ratio of 5:1, a KMnO ₄ dosage of 0.008 g/g (for raw materials), a sulfuric acid concentration of 3.6 mol/L, and a leaching time of 5 h. It reached 90.09%, and the copper leaching rate reached 97.81%. The leachate can further extract bismuth and copper.