Indium of the wet metallurgy
The output of non-ferrous metal smelters and chemical plants dust, slag, anode slime and acid mud indium extraction of raw materials. Replacement the indium law is a world process, in order to obtain the commodity crude indium. Containing indium raw material after acid leaching solution containing indium (such as low indium content in the liquid through the extraction of indium-rich solution).
As the solution prior to replacement of indium impurity profile or iron filings drop of copper and arsenic, to keep their solution [Cu] / [As] = 2.5, 15 ~ 30g / L free acid and 70 to 90 ℃ to Cu3As2 form to remove copper and arsenic residues [As] <0.02g / L in solution, in order to ensure subsequent replacement of indium will not appear the AsH3 poison; or copper, arsenic and antimony were the sulfide residue access to the solution of H2S removed ; or lack of added zinc powder amount, or to replacement in addition to copper, lead, tin, Fang sent replacement indium plus advance replacement sponge indium. More indium electrode potential more negative metal (Me) (table), commonly used in zinc and aluminum from the solution in indium replacement (reduced to metal):
In3 + + Me ==== In0 ↓ + Me3 +
Replacement control: replacement indium HInCl4 solution should join NaCl or HCl, the concentration of chloride ions in the solution of about 20g / L, pH = 1.5 to 2, the temperature of 40 to 50 ℃, replacement slot to maintain negative pressure ventilation, replacement, zinc and aluminum (such as zinc, and its replacement solution for the ZnCl2 solution, zinc is generally up to 170 ~~ 200g / L, a little zinc to adjust the the ZnCl2 grade can be obtained goods of ZnCl2; such as In2 (SO4) 3 indium solution replacement, should be also added NaCl up to 10 g / L, and to maintain H2SO415 ~ 50g / L, temperature 30 to 40 ℃, zinc or aluminum replacement.
Generally about 8 ~~ 24h replacement is completed, scraping obtained containing indium of about 90% to 95% of the sponge-like indium, storage to oxidation in the water. The mold when they remove from the water by the pressure group, into the stainless steel pot and covered with approximately the weight of 50% ~ 60% of the indium alkali, heated to 320 to 350 ℃ melting 2 ~ 3h, impurities (Me ‘) into the residue and the In ≥ 99% of crude indium.
Me ‘(II) / Me’ (III) +2 NaOH ==== Na2Me’O2 / 2NaMe’O2 + H2 ↑
The replacement indium method is simple, economic, applicable.
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