nursecosmo wrote:
kdlewis1975 wrote:
The activated charcoal/carbon filtering might work, but the activated alumina or silica gel (this is quite expensive) would probably work a whole lot better. Activated carbon works well if the species in question would prefer to adsorb to that rather than stay in solution. Given that this class of dyes are very insoluble in water and quite soluble in oils, I think the color will diminish a little, but will be still be prominent. Because I didn't know the structure, I did a search on the name of the dye. There are many variants. I think the basic version of the alumina would be the way to go in most cases, though some of the variants would probably prefer to stick to the acidic version of the alumina. I don't know enough about the zeolites to have a feel of how well that works or which variety would be appropriate. Alumina, because of its ability to be acidic or basic is pretty magical in the things it can do. The smaller the particle size the better since one would want as much surface area as possible.
Just out of curiosity...if someone makes and runs biodiesel but mixes onroad diesel in it, will this make Uncle Sam feel better about the tax thing? In reality, taxes were probably paid on the methanol and catalyst used to make it, though I understand how they could feel as if they're getting cheated out of their full compliment of road taxes.
The chemical name for Sudan red is amethoxybenzenazo-β-naphthol and should have a high afinity for carbon, seeing as how it is a Thiol. I don't currently have any red diesel on hand but may pick some up this week for testing.
I think that the activated carbon route may be effective because if I add even a small amount of WMO to my fuel mix, it doesn't just turn the mix black, it seems to remove all red color.
This appears to be one you're talking about:
http://en.wikipedia.org/wiki/Sudan_Red
This is apparently another variant that can be used in fuel:
http://en.wikipedia.org/wiki/Sudan_Red_7B
These are just the ones I found where a structure is posted, but there are apparently a lot of variants given some of the other names a I saw. Thiol implies a compound has a sulfur (-SH group specifically). It appears that the general motif for these compounds are the naphthalene ring bonded to an azide bonded to a benzene ring with each of those rings having various other things attached. These things have already demonstrated their affinity for carbon by being soluble in a sea of them (the diesel fuel), and they could like activated carbon more, but it's going to be a well-matched tug of war.
If your WMO isn't just masking the color, it could be catalyzing the destruction of the compound because of the trace metals in it. There could also be a chelating effect since the naphthol/phenyl and nitrogen moieties may have a good affinity for the metals and may decide to become ligands and form complexes with them. For many things like these dyes, a little goes a long way in terms of imparting color, so the silver lining is that there may not be much that needs to be removed. If there was a safe way of heating the fuel for a while, these would decompose by liberating nitrogen once termed by my professor as the best leaving group known to man. It generally doesn't take much to destroy an azide (the N double bond N structure) because it desperately would rather grow up to become N2...this why many explosives have lots of azide types of bonds in them and why airports screen for nitrogen compounds.
In the case of the G-version, I was thinking basic alumina could be effective because it deprotonate the naphthol and encourage it to bind to the filter media. In the case of 7B, acidic alumina may work better because it could protonate the amine (NH-group) on the naphthalene ring and encourage it to bind to the filter media. Just some thoughts. It would work out most conveniently if the activated charcoal/carbon works.
When I've used activated carbon in the lab, I've actually heated the vessel (50 C or so) containing my stuff and I'm always amazed at how much water condenses on the sides of the flask. I was using 2 wt% black stuff. So, just be heads-up, you could be introducing a fair amount of water to the system because the carbon can be pretty wet. ...and on top of that, I'd be disappointed because the final product was only slightly less yellow than I started with and generally have a terrible time getting the stuff back out. It's always annoying to do all of that work to only obtain a marginal benefit.
Celite is something that may be of use too. Celite is diatomaceous earth...as one of my former professors put it, "Fossilized little sea creatures who gave their lives to further chemistry." It has decent surface area and is primarily silica-based. It will adsorb some things, but it's typically used as a filter media....oh, for removing things like activated carbon.
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