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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SX Phase separation tests (3 replies)

(unknown)
8 years ago
(unknown) 8 years ago

I was doing some phase separation tests in the lab today and we saw that separation is faster when adding organic to the aqueous at a slower rate (while stirring the aqueous). Any way i can relate this back to the plant? Our A: O ration is 1.2:1, but both feed into the mixer impeller so the essentially feed at the same rate.

(unknown)
8 years ago
(unknown) 8 years ago
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Yes, we have seen and can reproduce the same phenomena in our lab. The cause is in homogeneity of concentration of the dispersed phase in the vessel, which contributes to a wide distribution of droplet sizes and can even provoke local inversion of the emulsion.

The wide droplet size distribution increases disengagement time by 2-5 times.The emulsion inversion creates a double emulsion, which separates an order of magnitude slower (typically 30 min instead of 2 min), and the separated liquids are usually turbid.
Turbulent Technologies designs mixing systems for SX with special emphasis on completeness of separation whilst maintaining good mass transfer. One important parameter of our systems is the homogeneity of the energy dissipation in the whole tank volume.

(unknown)
8 years ago
(unknown) 8 years ago
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When i added organic slowly to aqueous it separated nicely, but adding aqueous to organic had the opposite effect. I suppose this indicates that aqueous continuous is the best operating setup?

(unknown)
8 years ago
(unknown) 8 years ago
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The choice of continuity is complicate question, where many factors have to be considered - mass transfer, separation rate, which phase should be cleaner after separation etc.

Regarding organic in aqueous: it happens, when a system is more stable with one continuous phase than with another. There is a model which extensively used in the cosmetics industry - "hydrophilic-lipophilic balance" (HLB) that explains this. According to this, the more stable continuity may change with additives.


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