Abstract:Processing conditions of effectively separating indium from the leaching solution of a smelting antimony slag were researched. For the leaching solution of containing indium, antimony and iron ions, indium from the leaching solution by extracting indium ion with P204-kerosine solution, washing antimony And iron ions with H ₂ C ₂ O ₄ *2H ₂ O solution and stripping indium with a dilute solution of hydrochloric acid was separated. InCl ₃ solution with purity above 90% is obtained. Indium can be concentrated through stripping with HCl solution. Content in InCl ₃ solution is about 25~30g/L.

Key Words:Leaching solution of containing indium, Separating indium from antimony and iron ions, Concentration of indium

Indium is a metal having important uses genus ^[1], widely used in electronics, atomic energy and chemical industries, manufacturing fusible alloy and the like. Indium content in the crust of only 1 × 10 ^-7, and a large degree of dispersion, other metals typically associated ores, such as sphalerite, galena, etc. Therefore, the main raw material is indium recovery process metal smelting slag , soot, soot, etc. At home and abroad have been successfully recover indium from zinc smelting slag, copper ash and other materials but not been reported recovery of indium from antimony smelting slag. This study reports a method for efficiently recovering indium from an indium-containing and antimony leaching solution. Given the high rate of extraction of indium P204 extractant, the extraction higher acidity, wide availability ^[2-4], still uses P204- extracted coal oil; leachate low indium content, and antimony, a high iron content, for The ruthenium entering the organic phase is washed and removed with an oxalic acid solution; the iron in the organic phase is characterized by the reverse stripping of indium and iron under different concentrations of hydrochloric acid, and the indium is deionized with a low concentration of hydrochloric acid, and the iron is stripped with a higher concentration of hydrochloric acid. The purpose of separating indium from iron is achieved, and the organic phase is regenerated; the supported organic phase is back-extracted with dilute hydrochloric acid to achieve the purpose of enriching indium.

First, the test

(1) Instruments and reagents

WYX-2 Atomic Absorption Spectrometer (Shenyang Analytical Instrument Factory). 72G spectrophotometer (Shanghai Analytical Instrument Factory). THZ-82 constant temperature oscillator. P204, chemically pure (Shanghai Chemical Reagent Factory). Sulfonated kerosene, commercially available kerosene is sulfonated with concentrated sulfuric acid, and washed with Na ₂ CO ₃ solution and distilled water until neutral. The remaining reagents were homogeneously analyzed and purified.

(2) Test methods

The oil and water phases are placed in a separatory funnel at a certain ratio, and the time required for shaking on the oscillator is analyzed. After standing and layering, the contents of indium, antimony and iron in the aqueous phase are analyzed, wherein low content of indium and antimony is contained. Determination by atomic absorption spectrometry; high content of indium was determined by EDTA complexometric titration; high content of iron was determined by K ₂ Cr ₂ O ₇ titration; low content of iron was determined by phenanthroline spectrophotometry. The extraction rate was calculated by subtraction.

Second, the results and analysis

(1) Composition of indium-containing leachate

After the complex indium-containing bismuth slag is leached with dilute sulfuric acid, the composition of the leaching solution is shown in Table 1. The acidity of the residual acid (H ⁺ concentration) of the leachate is 0.6 to 0.8 mol/L. It can be seen from the data in the table that the content of Sb ³⁺ , especially Fe ³⁺ (Fe ²⁺ ) in the leachate is high, and the indium, antimony and iron are all trivalent ions, and the effect of antimony and iron on indium under extraction conditions Large, Zn ²⁺ , Ca ²⁺ , Na ^{+ ,} etc. are not extracted. Therefore, the separation of indium from antimony and iron is the key to making a purer InCl ₃ solution.

Table 1 Composition of indium-containing leachate (cation)

(2) Conditions for extracting indium from P204-kerosene solution

Using 30 vol% P204 sulfonated kerosene solution, the extraction time was controlled for 5 min according to O/A=1/3, and the extracts of different acidity were extracted to investigate the extraction of indium, antimony and iron under different acidity. see picture 1.

Figure 1 Effect of acidity on the extraction of indium, antimony and iron

1-indium; 2-inden; 3-iron

It can be seen from Fig. 1 that the indium has a high extraction rate (greater than 92%) in the acidity of the leaching solution of 0.3-0.7 mol/L, even if the leachate is directly extracted (acidity is about 0.7 mol/L), one-time extraction of indium The rate is also up to 92%. For hydrazine, only 60% is extracted, while the iron extraction rate is less than 3%. Therefore, it was determined that the leachate was directly extracted with the P204-sulfonated kerosene solution without previously adjusting the acidity of the leachate. The extraction rate of indium can be further increased by increasing the number of extraction stages. The test proves that after three-stage countercurrent extraction, the extraction rate of indium is above 99%, the extraction rate of bismuth is about 80%, and the extraction rate of iron is 5%.

The extraction equilibrium time test (see Figure 2) shows that the extraction of indium by P204-kerosene solution can be balanced within 5 min; the extraction rate of iron increases gradually with time, and the equilibrium time is longer; the extraction equilibrium time of rhodium is more than that of indium. Short, but the extraction rate is low, so the effective extraction time is controlled to be 5 min. The extraction conditions determined for the indium-containing leachate were: 30% P204-sulfonated kerosene solution, O/A = 1/3, extraction equilibrium time 5 min, and the extracted aqueous phase was the leaching original solution. Under these conditions, the composition of the supported organic phase after one extraction was In 0.91 to 0.96 g/L, Sb 0.90 to 1.0 g/L, and Fe 1.5 to 1.6 g/L.

(2) elution of ruthenium in the supported organic phase

Figure 2 Relationship between extraction time and extraction rates of indium, antimony and iron

(O/A=1/3; 30% P204-kerosene solution)

1-indium; 2-inden; 3-iron

After the extraction according to the above extraction conditions, the content of indium and antimony in the supported organic phase is equivalent, and the iron content is slightly higher. In order to remove the ruthenium in the organic phase, after repeated trials, the oxalic acid solution is used to wash the mites. A series of different concentrations of oxalic acid solution were prepared, and the loaded organic phase was subjected to a washing test at a ratio of 1:1. The results are shown in Fig. 3.

Figure 3 Relationship between oxalic acid solution concentration and enthalpy elution rate

As can be seen from Figure 3, the oxalic acid solution has a good effect of washing. When the concentration of the oxalic acid solution is above 20 g/L, the washing effect is basically the same, and the primary elution rate of the hydrazine is above 90%, so the concentration of the oxalic acid solution in the washing solution is determined to be 20 g/L. The organic phase was washed twice in succession according to the above washing conditions, and the elution rate of cerium was over 99%, while the elution rate of indium was close to zero, and the elution rate of iron was about 18%. It can be seen that the selection of the oxalic acid solution to wash the supported organic phase can remove most of the bismuth, and the indium has almost no loss, achieving the purpose of separation of indium and bismuth. After the organic phase is washed with an oxalic acid solution, the composition is In 0.91 to 0.96 g/L, Sb 0.01 to 0.02 g/L, and Fe 1.2 to 1.3 g/L.

(4) Indium back extraction

After washing with oxalic acid solution, the main components in the supported organic phase are indium and iron. The two ions can be stripped under different concentrations of hydrochloric acid, and different hydrochloric acid concentrations can be controlled to carry out back extraction. Figure 4 shows the relationship between the stripping rate of indium and iron and the concentration of hydrochloric acid.

Figure 4 Indium and iron stripping rates at different HCl concentrations

(O/A=5/1; stripping time 5min)

1 — indium; 2 — iron

The results show that the stripping rates of indium and iron increase with the increase of hydrochloric acid concentration, but the stripping rate of indium has reached more than 88% when the concentration of hydrochloric acid is 2mol/L, but the stripping rate of iron is not Up to 5%; when the concentration of hydrochloric acid is 3mol/L, the stripping rate of indium reaches 92%, and the stripping rate of iron is only about 15%, so that the concentration of hydrochloric acid can be separated by controlling the concentration of hydrochloric acid during stripping.

The stripping time test results (see Figure 5) show that when indium is stripped with 2 mol/L HCl, the equilibrium can be reached within 10 min. Therefore, the back extraction time is determined to be 10 min.

Fig. 5 Relationship between stripping rate and stripping time of indium (HCl 2mol/L; O/A=5/1)

Thus, the final determined stripping conditions were: HCl 2 mol/L, stripping compared to O/A = 5/1, and stripping time 10 min. According to such stripping conditions, the inversion rate of indium is above 92%. After three-stage countercurrent stripping, the stripping rate of indium can reach over 99%. After the washed organic phase is subjected to back extraction, the resulting stripping solution has a composition of In 4.2 to 4.4 g/L, Sb 0.05 to 0.1 g/L, Fe 0.3 to 0.32 g/L, and InCl ₃ purity of 90% or more.

(5) Circulating back extraction test

In order to prepare a solution of InCl ₃ with higher purity and a larger concentration, the washed organic phase is subjected to cyclic back extraction test according to the stripping conditions of Section 2.4. After 3 cycles of the stripping solution, the following composition is obtained. InCl ₃ solution: In 25 to 26 g/L, Sb 0.3 to 0.6 g/L, and Fe 1.8 to 1.9 g/L. This solution can be directly reduced to obtain sponge indium.

Third, the conclusion

1. The P204-sulfonated kerosene solution was used to directly extract the indium-containing leaching solution, and the extraction time was controlled for 5 min. The indium had a higher extraction rate, while the iron extraction rate was very low, achieving the purpose of preliminary separation of indium and iron.

2. The extracted organic phase was washed with an oxalic acid solution at a concentration of 20 g/L. After two consecutive washings, more than 99% of the ruthenium was eluted, and the indium was almost not lost, achieving the purpose of separating indium and bismuth. .

3. Back-extraction of the washed organic phase with 2mol/L HCl, the inversion rate of indium is above 88%, the third-stage stripping rate is above 99%, and the stripping rate of iron is low, further separating indium. And iron, the purity of InCl _{3 in} the prepared stripping solution is over 90%.

4. By back-extracting with 2mol/L HCl, the indium in the stripping solution can be enriched, and the InCl ₃ solution containing 25-30 g/L of indium can be obtained, which provides a possibility for further reduction of sponge indium.

references

[1] Zhou Jingyuan. Hunan Metallurgy, 1984, 36(4): 36
[2] Song Yulin. Rare Metals (Domestic Edition), 1982, 6(1): 35
[3] Yao Genshou. Nonferrous Smelting, 1994, 23(4): 52
[4] Yao Changhong. Hunan Nonferrous Metals, 1996, 12(2): 58

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