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Topic: Flocculating Agents for basic pH applications  (Read 4106 times)

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Offline curiouscat

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Flocculating Agents for basic pH applications
« on: February 16, 2013, 02:34:56 AM »
I was looking for a flocullating agent that'd be stable at high pH (~11). Normally, I'd use Alums, Ferric / Ferrous Chlorides or Sulfates but all of those seem to work best at neutral or slightly alkaline pH (pH 7-8.5 mostly reported).

Any ideas  which other agents might be good to try? The stream to be treated is  Oil + CaCl2 + H2O composition but with ~10% of suspended inorganic solids in it mostly CaCO3.

The particle sizes are fairly large; 50 microns and larger. The solids separate out easily in a lab centrifuge at modest g / rpm values.

I've seen Polyacrylamides reported as flocculating agents but not sure what their basic medium stability is.

Offline billnotgatez

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Re: Flocculating Agents for basic pH applications
« Reply #1 on: February 16, 2013, 04:23:10 AM »
From a ceramics source
Quote
The most common flocculants potters use are epsom salts (magnesium sulfate) and calcium chloride, though acids (such as muriatic acid) can also be used
I assume this does not apply in your case.

Offline curiouscat

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Re: Flocculating Agents for basic pH applications
« Reply #2 on: February 16, 2013, 04:36:29 AM »
From a ceramics source
Quote
The most common flocculants potters use are epsom salts (magnesium sulfate) and calcium chloride, though acids (such as muriatic acid) can also be used
I assume this does not apply in your case.

I could try magnesium sulfate. CaCl2 I already have oodles of right in there.

HCl's a no go. Cannot go to acidic pH. The oily phase needs to remain alkaline for stability reasons.

Offline billnotgatez

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Re: Flocculating Agents for basic pH applications
« Reply #3 on: February 16, 2013, 05:10:14 AM »
Is it typically true, that a base environment is deflocculating and going towards neutral is flocculating?

Offline curiouscat

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Re: Flocculating Agents for basic pH applications
« Reply #4 on: February 16, 2013, 05:19:51 AM »
Is it typically true, that a base environment is deflocculating and going towards neutral is flocculating?

Never heard of that. But its a complex field and I'm no expert.

I doubt the trends are monotonic. From what I read a lot of water treatment flocs form best between pH 7-8.5.

Offline curiouscat

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Re: Flocculating Agents for basic pH applications
« Reply #5 on: February 16, 2013, 07:31:46 AM »
I tried adding potash alum (KAl(SO4)2.12 H2O) and there seems a gelatinous ppt that forms. Wonder if this might be AlCl3?

Al2(SO4)3 + 3  CaCl2  :rarrow: 2 AlCl3 +  3 CaSO4

Is this reaction to be expected?

Offline Borek

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Re: Flocculating Agents for basic pH applications
« Reply #6 on: February 16, 2013, 07:46:20 AM »
Gelatinous in the context of presence of Al makes me think about Al(OH)3.
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Offline curiouscat

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Re: Flocculating Agents for basic pH applications
« Reply #7 on: February 16, 2013, 08:02:33 AM »
Gelatinous in the context of presence of Al makes me think about Al(OH)3.

You must be right. AlCl3 has a high solubility in H2O. Al(OH)3 does not.

I wonder what'd be a good flocculating agent in this situation. I suppose Fe-chlorides and Fe-sulfates will form hydroxide ppts too.  :-\

Offline billnotgatez

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Re: Flocculating Agents for basic pH applications
« Reply #8 on: February 16, 2013, 10:49:38 AM »
http://www.flocculants.info/polymer-definitions.html

This page suggests
calcium salts at pH between 4 and 14
iron salts at pH between 4 and 13
aluminum salts at pH between 4.5 and 10

If you use
Polyethylene-imines
Polyamides-amines
Polyamines
Polyethylene-oxide
are we then talking organic chemistry?


Offline curiouscat

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Offline billnotgatez

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Re: Flocculating Agents for basic pH applications
« Reply #10 on: February 16, 2013, 09:01:38 PM »
Potters flocculate alot  ;)

Offline ajkoer

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Re: Flocculating Agents for basic pH applications
« Reply #11 on: February 27, 2013, 12:29:18 AM »
Try Ammonium iron(III) sulfate, NH4Fe(SO4)2ยท12 H2O, also known as ferric ammonium sulfate (FAS) or iron alum. Highly soluble and less acidic than Aluminum sulfate.

Now in the presence of CaCl2. I think we get NH4Cl, CaSO4 and Fe(OH)3. Also, I like the idea of an ammonium salt with oil (also presence).

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