Wet sulfation indium

After the indium- containing material is subjected to calcination with concentrated sulfuric acid, the indium is converted into a sulfate and then recovered. The raw materials to be treated are mostly indium-containing soot and other materials, and the main components (mass fraction ω/%) are: indium 0.003 to 0.006, 铊 0.056 to 0.130, selenium 0.21 to 0.28, 碲 0.06 to 0.11. Lead 48.0 ~ 54.5, zinc 7.3 ~ 15.2, cadmium 1.8 ~ 2.2 and sulfur 5.1 ~ 6.6. The process flow is shown in the figure.

Wet sulfation roasting process

The process comprises mixing the indium-containing material with 1.1 times of concentrated sulfuric acid and 1% to 3% of charcoal to prepare a granular charge having a diameter of 3 to 5 mm. The charge was calcined and calcined at a temperature of 573 K for 60 min in a fluidized roaster (see fluidized roasting). Indium material during firing and heavy metal oxides (MeO) into almost all sulphate:

In ₂ O ₃ +3H ₂ SO ₄ =In ₂ (SO ₄ ) ₃ +3H ₂ O MeO+H ₂ SO ₄ =Seoxide in the MeSO ₄ +H ₂ O material is volatilized in the form of SeO ₂ and is reduced by SO ₂ in the leaching tower. Recovered for monomeric selenium. Impurities such as fluorine, chlorine and arsenic are mostly volatilized and removed during the calcination process.

The produced calcine is leached with a waste electrolyte or a sulfuric acid solution. Under the liquid-solid ratio of 3:1, the acidity of the solution end point containing free acid 10g / L, leaching for 1h, to obtain acid leaching solution containing indium 0.012g / L, é“Š 0.18g / L, zinc 42g / L and cadmium 15g / L . The acid leachate was then neutralized with ZnO at a temperature of 318 to 323 K to the extent that almost all of the indium and cerium precipitated. The obtained neutralized slag is enriched in indium to 0.2% to 0.6%, and the balance is zinc and cadmium. The neutralized slag is further leached with sulfuric acid. When the acidity of the leaching solution reaches 30-40 g/L of free acid, the indium is dissolved, and the hydrazine remains in the slag to realize separation of indium and bismuth. The acid leachate was extracted with D2EHPA and back extracted with hydrochloric acid. The obtained indium stripping solution was replaced with zinc powder to obtain sponge indium. The sponge indium is electrolyzed to obtain a metal indium having a purity of 99.99%.

In the former Soviet Union, Usti Kaminorgorsk lead-zinc joint venture and Chelyabinsk zinc plant used indium-containing materials after wet sulfation roasting to recover indium by solvent extraction and ion exchange, respectively. About 90%.

It is expected that this method has the advantages of short process, easy production, and the removal of harmful impurities such as fluorine, chlorine and arsenic. However, in the case of sulphation roasting, it is necessary to incorporate concentrated sulphuric acid to cause poor operating conditions and serious corrosion of equipment. A thousand sulfation process using FeSO ₄ instead of concentrated sulfuric acid has been developed. In addition, the calcination calcination calcination, after water leaching, the solvent extraction or ion exchange method is used to replace the process of enriching and dissolving the indium in the original process, and the recovery rate of indium can be further improved.

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