Pyrometallurgy: Roasting, Smelting, Refining & Electrowinning

Pyrometallurgy: Roasting, Smelting, Refining & Electrowinning 2017-04-21T02:33:06+00:00
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Making zinc sulphate (12 replies and 2 comments)

Dizzy Flores
2 years ago
Dizzy Flores 2 years ago

Hi my zinc sulphate manufacturing process, I am having Zinc dross containing 4% Iron. To make pure Zinc sulphate solution we have to remove Iron. Is there any solvent available to separate Iron from Zinc?

John Koenig
2 years ago
John Koenig 2 years ago

D2EHPA is able to selectively extract Fe (III) ahead of Zn, but it is not readily stripped with H2SO4 and it is necessary to use 6 M Hcl for stripping. M2EHPA can also be used for this application, but I am not sure whether M2EHPA is still commercially available. Other organ phosphorus extractants, such as Ion quest 801 or Cyanex 272, can also perform this separation, and can be stripped with sulphuric acid, but the reagents are more expensive. Most zinc flow sheets, however, remove iron from zinc by precipitation using limestone at pH 3.

Carmen Ibanz
2 years ago
Carmen Ibanz 2 years ago

Remove Iron and other impurities from PLS by precipitation with limestone pH > 3 , them, extract Zn using D2EHPA from cleaning PLS.Strip end concentrate Zn using clean zinc electrolyte sulphuric acid media.

4 months ago

Mam, theoretical it is ok but in my point of precipitation lime creates problemin SX extraction

Helena Russell
2 years ago
Helena Russell 2 years ago

Up to what concentration (say in gm per liter) can we reduce Iron from a Zinc Iron Sulphate solution using lime stone powder? I suppose no Zinc will precipitate out at 3 pH.

It may not be proper in S/X to use HCL in a sulphate medium. Therefore D2EHPA may not be suitable.Ion quest 801 or Cyanex 272 can be used but I am not aware which companies manufacture or where to buy these chemicals from. If someone can help?

Ace Levy
2 years ago
Ace Levy 2 years ago
Victor Bergman
2 years ago
Victor Bergman 2 years ago

One can certainly remove Fe of several g/L using limestone. You are correct that Zn does not precipitate at this pH. It is possible to use D2EHPA but the strip circuit should be kept separate from the extraction circuit and you need to make sure that your materials of construction are compatible with chloride and that minimal chloride is transferred to the extraction circuit. Cyanex 272 is available from Cytec and Rhodia produces Ion quest 801. It will also depend on the pH of your starting solution which extractant would work better for you. I suggest setting up a formal test programme to evaluate the options, starting with the precipitation removal suggestion.

Carl Jenkins
2 years ago
Carl Jenkins 2 years ago

Yes, I agree with your observations and it is a wise thing to start a test program.

Maya Rothman
2 years ago
Maya Rothman 2 years ago

You can ensure the purification with ion exchange (after precipitation or solvent extraction) if one of your requirements is remove all iron (III) in solution.This option is efficient if the concentration of ions is not too high.

Zander Barcalow
2 years ago
Zander Barcalow 2 years ago

We don't need that high level of purification; 5 to 50 ppm should be OK.

Alan Carter
2 years ago
Alan Carter 2 years ago

Withregards Limestone precipitation. There are a few issues to consider.

Firstly, the iron in solution must be Ferric. Ferrous precipitates at equivalent pH to zinc. It is typical that air is introduced to iron precipitation reactors to oxidise iron.

Iron Hydroxide precipitates are notoriously difficult to filter. It is normally preferable (though not financially so) to carry out the precipitations at elevated temperatures to encourage the formation of Goethite’s or else to introduce anions (Na, K) that encourage the formation of jarosites

While it is true that significant zinc will not precipitate at pH 3, you will still entrain zinc solution in the solids. If you have significant amounts of iron - your original post states 4% - your zinc losses could be significant. Limestone is also not an efficient base (but it is economical), so you could end up with quite a voluminous precipitate/unreacted limestone solid phase. You may well need some washing stages to recover the zinc, which might affect your water balance.
SX, though not the usual first choice for primary iron control may be a strong contender in your case.

4 months ago

Dear Sir, very good explanation as you given, exactly in all plants are facing same problems are facing, SX running after the neutralization with lime as creates problem in extraction

Jean Rasczak
2 years ago
Jean Rasczak 2 years ago

Is it expensive to try distillation? I am sure that your iron will not follow.

Tony Verdeschi
2 years ago
Tony Verdeschi 2 years ago

Distillation may be expensive. To my humble opinion, I think that it is a good idea to try to proceed with solvent/extraction.

4 months ago
K@TTU 4 months ago

If high Zinc concentration Streams having Zn 45-50 g/l  using SX with D2PHA is economically suitable process with neutralization with caustic . In our process stream has contain high Mg and Mn levels so we have separate out from the impurities by SX method to extract Zn and bleed stream discard to ETP.

The Feed of SX process is obtained by neutralization with lime to produce gypsum, but this neutralized as create problem to SX because of lime impurities specially Silica.   

Please suggest this process has scope of economical reject of Mn & Mg from Zn electrolyte. 

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