Hydrometallurgy: Leaching in Heap, Vat, CIL, CIP, Merrill–Crowe, SX Solvent Extraction

Hydrometallurgy: Leaching in Heap, Vat, CIL, CIP, Merrill–Crowe, SX Solvent Extraction

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by-products/wastes in metal recovery processes (1 reply and 2 comments)

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Filip_D
6 years ago
Filip_D 6 years ago

Hello,

I am doing research on hydrometallurgical metal recovery (as well as more conventional metal recycling) within the industry and I hit a wall. I am able to identify technologies employed, as well as the amount of processed materials in both areas, however I cannot find anything about by-products or wastes resulting from the processes. All companies I have researched tend to showcase their tech and how they are able to reduce contamination, etc., but they never specifically give information about the amount of wastes generated, how much of the processed materials becomes waste and how it is stored. I am especially interested in sulphate effluents. Do you perhaps have any tips how to deal with this issue/identify the desired data? (Contacting companies by email does not work).

Thank you for your help.

Best regards

Filip

Ron G
6 years ago
Ron G 6 years ago
1 like by David

Filip, you don't mention what cations or other anions are in your waste. Most metal sulfates will precipitate as hydroxides or oxides with alk neutralization up to ~PH 8. I like to use carbonate rather than lye (NaOH) since it is cheaper and less hazardous. It also provides carbonate anions, which many metal are more insoluble to. After a day of settling the PH 8 liquid can be separately transferred to another tank or drum for mixing with particular anions that are even more insoluble. For example, pyrophosphate forms some particularly insoluble metal precipitates. I mix my precipitate electro-polish waste for a second precipitation by mixing it with my waste pyrophosphate electro-cleaner.

In the absence of online lit it's easy to experiment in beakers to see if you can get further precipitates. After all, it would be going down the drain anyway in not trying the test. I am not sure that resulting sodium sulfate, once the metal is removed, is a concern for going down the drain. I could be wrong. I know that barium will drop out 99.9% of sulfate and will settle and filter nicely. You can use BaCl2 but you are still putting saline down the drain. I welcome other comments.

Ron G
6 years ago

If you neutralize first to the PH point before the first metal precipitate with calcium oxide (quick lime) the sulfate will drop out as calcium sulfate dihydrate to the point of 2.4g/l solubility. Then neutralize maybe with hydroxide or carbonate or both to recover different metals.

F
Filip_D
6 years ago

Thank you, however this is a bit too specific. What I am looking for are information on an industry-scale level. How much waste is generated and what type, during a plant's annual operations for example.


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