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Leaching Process

by zorro
Tags: leaching, process
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zorro
#1
Oct9-10, 02:32 PM
P: 1,394
In the Leaching process of Aluminium, alumina present in bauxite dissolves forming a soluble sodium aluminate. The impurites are filtered off. The filtrate is diluted and a little freshly precipitated aluminium hydroxide is added which causes the precipitaion of aluminium hydroxide.

How does it cause the precipitation of aluminium hydroxide? According to Le Chatelier's Principle backward reaction will occur consuming aluminium hydroxide. What is the actual reason?
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alxm
#2
Oct9-10, 06:09 PM
Sci Advisor
P: 1,866
The solution becomes over-saturated because the leaching is done at a high temperature, which is then lowered. Adding some solid aluminum hydroxide creates nucleation points for the precipitation.

(While we're on the subject, it's worth noting that those filtered-off impurities just spilled out all over in Hungary)
zorro
#3
Oct10-10, 04:44 AM
P: 1,394
Quote Quote by alxm View Post
The solution becomes over-saturated because the leaching is done at a high temperature, which is then lowered. Adding some solid aluminum hydroxide creates nucleation points for the precipitation.
The solution becomes oversaturated with what? Aluminium Hydroxide?
Please elaborate 'nucleation points'.


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