Flocculation Flocculation

Transcription

Flocculation Flocculation
Flocculation
• Flocculation is: The agglomeration of
destabilized colloidal particles in the
“charge neutralization” mode, or The
agglomeration of floc particles
• Agglomeration is: Causing destabilized
particles, or floc to collide and to grow in
size
Flocculation
Flocculation is, in the field of chemistry, a
process where colloids come out of suspension
in the form of floc or flakes. The action differs
from precipitation in that, prior to flocculation,
colloids are merely suspended in a liquid and
not actually dissolved in a solution. in the
flocculated system there is no formation of a
cake since all the flocs are in the suspension.
The following chemicals are used as flocculants:
alum
aluminium chlorohydrate
aluminium sulfate
calcium oxide
calcium hydroxide
iron(II) sulfate
iron(III) chloride
polyacrylamide
polyDADMAC
sodium aluminate
sodium silicate
The following natural products are used as
flocculants:
Isinglass
Gelatin
Guar gum
Alginates (brown seaweed extracts
Deflocculation
A deflocculant is a chemical that is added to prevent a
colloid from coming out of suspension. (In this case
deflocculation is a desired effect).
Deflocculation is also used to describe the undesired
effect in an activated sludge basin if the sludge is
subjected to high-speed mixing. Generally,
deflocculation can be prevented or reduced by
applying gentle mixing(e.g., by using submersible
propeller mixers that utilize large/wide propeller
blades and operate at low rotational speed).
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