Leaching Process: Aluminium Hydroxide Precipitation

  • Thread starter Thread starter zorro
  • Start date Start date
  • Tags Tags
    Process
AI Thread Summary
In the leaching process of aluminum extraction from bauxite, alumina dissolves to form soluble sodium aluminate, while impurities are filtered out. The subsequent dilution and addition of freshly precipitated aluminum hydroxide lead to the precipitation of aluminum hydroxide. This occurs because the solution becomes oversaturated after being heated during leaching and then cooled. The introduction of solid aluminum hydroxide serves as nucleation points, facilitating the formation of aluminum hydroxide crystals. The discussion also briefly mentions environmental concerns related to impurities from this process, referencing a specific incident in Hungary.
zorro
Messages
1,378
Reaction score
0
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?
 
Chemistry news on Phys.org
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)
 
alxm said:
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'.
 
Thread 'How to make Sodium Chlorate by Electrolysis of salt water?'
I have a power supply for electrolysis of salt water brine, variable 3v to 6v up to 30 amps. Cathode is stainless steel, anode is carbon rods. Carbon rod surface area 42" sq. the Stainless steel cathode should be 21" sq. Salt is pure 100% salt dissolved into distilled water. I have been making saturated salt wrong. Today I learn saturated salt is, dissolve pure salt into 150°f water cool to 100°f pour into the 2 gallon brine tank. I find conflicting information about brine tank...
Engineers slash iridium use in electrolyzer catalyst by 80%, boosting path to affordable green hydrogen https://news.rice.edu/news/2025/engineers-slash-iridium-use-electrolyzer-catalyst-80-boosting-path-affordable-green Ruthenium is also fairly expensive (a year ago it was about $490/ troy oz, but has nearly doubled in price over the past year, now about $910/ troy oz). I tracks prices of Pt, Pd, Ru, Ir and Ru. Of the 5 metals, rhodium (Rh) is the most expensive. A year ago, Rh and Ir...
Back
Top