I'm faced with a situation where I have very fine sand dispersed in a solution. Now a decent filter with an low micron rating would probably do the
job, except some particulates are very very small. Was wondering if anyone knew of a good flocculant that works well with sand particles?sparkgap - 29-4-2008 at 16:36
Alum?
sparky (~_~)azo - 29-4-2008 at 16:50
Depending on the solution and the solubility of the substrate in that solution sand itself as a molecular sieve works very good.
azo.encipher - 29-4-2008 at 16:54
Quote:
Originally posted by azo
Depending on the solution and the solubility of the substrate in that solution sand itself as a molecular sieve works very good.
azo.
Umm... How so ?not_important - 29-4-2008 at 19:32
You didn't state anything about the solution, so I don't know if californium tetracyanide can be used, or if you just can add HF and HNO3 to dissolve
the 'sand', or what.
For potable water treatment iron or aluminium salts are commonly used, with the pH adjusted so as to have the hydroxide form; generally a little above
7, Ca(OH)2 solution can be used.
You should be able to just filter the stuff, though. Sand is big, large than 75 microns, even silt is is larger than several microns. I'd try a
coarser filter followed by a medium or fine (fritted glass specs). Or if the volume isn't too large, just centrifuge the puppy.
Particle sizes and fritted filter codes:
encipher - 30-4-2008 at 11:14
not_important, I tried 5 micron filter felt, that was about an 1/8 of an inch thick, and folded it four times, and the fine particles still goes
through. The solution will be purified so the end result has to be 'clean' water.12AX7 - 30-4-2008 at 12:20
Does it settle when you leave it alone for a week?
Oftentimes that's what I do.
Timencipher - 30-4-2008 at 13:46
12AX7,
Yeah it sure does settle, but I don't have that much time =) I'm positive a coagulant would work, but I am unsure as to what would be the best to use
that would not be toxic or hazardous.DrP - 1-5-2008 at 00:07
Quote:
Originally posted by encipher
Yeah it sure does settle, but I don't have that much time =) I'm positive a coagulant would work, but I am unsure as to what would be the best to use
that would not be toxic or hazardous.
Can you get use of a centrifuge then?not_important - 1-5-2008 at 06:33
If it gets through a 5 micron filter, and assuming the filter was correctly set up, then you're not dealing with sand or even silt, but rather clay
or rock flour like you find in glacier runoff.
However the use of 'folding' makes me wonder about the edge seal in your filtration attempt, with finer filters the resistance becomes high enough
that you need a setup that avoids leakage around the filter; usually along with applied pressure or vacuum. Household water filter cartridges
typically are rated in the 1 to 10 micron range, and have a noticeable back pressure.
As you've still not indicated anything like volume that needs treating, we're still shotgunning:
Use fine filters, or deep sand filters. Best if all you are treating is a few liters.
Centrifuge, batch or continuous.
Flocculates such as iron or aluminium salts, or prganic polymers, followed by filtration. See here for examples targeted at pools, when properly used
safe enough although maybe not satisfactory for drinking or cooking http://www.aquaclear.co.nz/swimmingpoolproducts.php?category...
These generally take a bit of time to work, the floc needs to form up before you can filter it, so expect minutes to hours.
As such your best bet is to look at systems for treating swimming pools, or household sized drinking water treatment as used in rural areas. For
batch mode you might look at something such as http://www.csrwire.com/News/11792.html while for larger amounts these might be better
that last is rated at 0,2 microns, down into the bacterial range, and might need a coarse prefilter to remove actual sand. Note that its initial
pressure drop is about one atmosphere, and will increase with use.
