Sulfated indium method
Indium- containing soot or slag (indium is mainly MeO), etc., is mixed with H 2 SO 4 , and is put into a boiling roaster or rotary kiln for sulphating and roasting to obtain In 2 (SO 4 ), and at the same time volatilizing to remove arsenic and fluorine, etc. Dry sulphation, China and Kazakhstan and other countries use wet type.
In 2 O 3 +3H 2 SO 4 ==== In 2 (SO 4 ) 3 +3H 2 O↑
Adding 110% concentrated sulfuric acid and 3% charcoal to the soot containing In 0.006%, Ge 0.004%, Tl0.056% and As 1.23%, granulating 3~5mm pellets, and putting into boiling boiling furnace at 300 °C baked, the indium, germanium, lead and thallium, zinc sulfate into. 85%~95% of arsenic, fluorine and selenium are volatilized into the flue gas, and can be comprehensively used after dust collection. In 2 (SO 4 ) 3 baking sand was dissolved in water at 80 ° C, liquid-solid ratio of 3, and terminal acid 10 g / L for 2 h. The obtained solution containing In 0.012 g / L and Tl 0.18 / L was neutralized with ZnO to pH = 3 ~4 hydrolysis to get In(OH) 3 :
In 2 (SO 4 ) 3 +6H 2 O ==== 2In(OH) 3 ↓+3H 2 SO 4
With H 2 SO 4 (control final acid H 2 SO 4 of 30 ~ 40g / L) dissolve the precipitate, the indium into the solution, the addition of copper sulfate and iron scrap arsenic removal when heated to 70 ~ 80 ℃, after filtration Residual acid H 2 SO 4 5g/L, substituted with zinc powder at 50~70 °C to obtain sponge indium, which was decomposed by H 2 SO 4 and electrolyzed to obtain 99% indium. The recovery rate is about 80%. Kazakhstan's Usti-Kamennogorsk Pb-Zn joint venture uses this method to recover indium.
Wet sulphation pollutes the environment and the human body, so the development of dry sulphate roasting at a temperature of 500 ~ 600 ° C with FeSO 4 generation concentrated H 2 SO 4 :
2In 2 O 3 +6FeSO 4 +3/2O 2 ==== 2In 2 (SO 4 ) 3 +Fe 2 O 3
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