Understanding Nucleation and Seeding in Precipitation Processes

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SUMMARY

Nucleation and seeding are critical processes in the precipitation of copper hydroxide (Cu(OH)2) from calcium hydroxide (Ca(OH)2) in sedimentation tanks. The discussion highlights that finely divided solid particles of Cu(OH)2 act as nucleation sites, promoting the growth of larger crystals. This process enhances slurry formation and improves separation efficiency during filtration. Recirculating the slurry back to the calcium feeding tank facilitates prolonged contact between the seed crystals and the copper solution, resulting in larger crystal growth and faster settling.

PREREQUISITES
  • Understanding of precipitation chemistry
  • Familiarity with sedimentation tank operations
  • Knowledge of crystal growth mechanisms
  • Experience with slurry handling and filtration processes
NEXT STEPS
  • Research the principles of nucleation in chemical processes
  • Study the effects of recirculation on slurry dynamics
  • Explore advanced filtration techniques for solid-liquid separation
  • Investigate the role of seed crystals in industrial crystallization
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Chemical engineers, process engineers, and anyone involved in precipitation processes and slurry management will benefit from this discussion.

lenin_yuweh
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Hi!

I seem to be out of the loop at work. Too embarrass to ask my coworkers to explain it to me.

Can anyone explain what nucleation and seeding is?

Our process is basically a precipitation process where copper is precipitated by reacting Ca(OH)2 to Cu(OH)2. We have a sedimentation tank to separate the slurry from the filtrate. What I don't understand is how recirculation, pump sucks the slurry below and returns it to the calcium feeding tank, improve slurry formation. They mentioned nucleation and seeding enhancement. I don't get how "crystals" can form in a slurry or is a slurry considered a crystals?
 
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Your slurry is likely a finely divided solid form of the Cu(OH)2 you seek. If these solids are crystalline in any way, they induce further solid to form on their surfaces. This causes the finely divided slurry form larger particles which are easier to remove by settling or filtration. So the initially formed very small particles induce the growth of a much larger particle. It is called "nucleation" or "seeding".

Pumping these growing "seed" crystals back to the Calcium feed tank let's those particles stay in contact with the copper solution longer thus allowing for larger crystal growth and a slurry that separates more quickly.
 

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