Removing carbon matter from molten beeswax

Question

In my candle manufacturing process, I melt down used candle stubs, filter the molten wax (heated to ~ $\pu{75^\circ C}$) and use this to create new candles (in addition to fresh beeswax). I'm currently using oil filter paper to gravity filtrate the molten wax, this does a good job of removing the larger carbon particles but doesn't remove all carbon matter.

Is there a chemical process that I can use to perhaps make the carbon elements heavier, to allow them to sink to the bottom, and harvest the cleaner molten wax from the top?

Edit: http://www.dave-cushman.net/bee/waxdecont.html talks about melting wax in water just below boiling and adding hydrogen peroxide. Another filtering option mentioned in the article is dissolving beeswax in carbon tetrachloride (CCl4) which is meant to result in the liquid flowing more readily through a filter. If these are realistic options, guidance would be appreciated on the approach / amounts to use with these approaches.

• I have tried coffee filter paper, besides it taking much longer to filter, it made no notable difference.
• I have experimented with leaving the molten wax for longer periods of time undisturbed, and scooping from the top. This worked well if the stubs were left to melt undisturbed until molten, and scooped from the top. It made no difference if the wick/soot was disturbed during the melting process or when processing the 'dregs' at the bottom that were full of soot. See photo of the difference. Although I'm able to process a significant amount of stubs without disturbing the soot, I still need a process to clean this soot stained beeswax.

Both samples originate from the same shade of candles. I can confirm this is soot stained beeswax (on the left), and not overheated beeswax (which discolors when exposed to high temperatures). Color of the beeswax on the right is of satisfactory shade, and very close to the original color of both samples.

Answer 1

Hydrogen peroxide as suggested will possible just bleach the particles, not remove them. I think also, that the miscibility with an aqueous solution and wax may be a problem here. There are probably other bleaching agents that could be used. Be aware that this agent may lead to oxidation of metal pots. CCl4 (carbon tetrachloride) is cancerogenic and not advisable here.

From my point of view, melting the wax and let it flow through a filter medium may not be the optimal solution, because the fluidity will at some point decrease and the wax may have problems passing through the filter when it goes back to solid form.

However, pillow cloths may work well as a filter media when you have a sufficient big amount that will not solidify before going through the filter (bigger amount equals a bigger heat capacity).

https://m.youtube.com/watch?v=-1pc8lMrsYM&pp

In addition I found a guide, were the wax is put in a mesh, and this mesh is heated in water. The wax will liquidity and the solid contaminations will stay in the cloth. You could perform this cleaning multiple times with finer meshes to achieve better cleaning.

https://backyardbeekeeping.iamcountryside.com/honey-beeswax/steps-for-filtering-beeswax/

If you have access to a centrifuge you could try to melt the bee wax and centrifuge the molten wax. The particles should sink to the bottom if they have higher density.

Alternatively one could try to use a "not-so toxic" solvent like acetone, ethyl acetate or ether (all of them are flammable, ether is very volatile so proceed with caution and avoid open flame) to dissolve the bee wax and then filter the liquid. The solution would have less viscosity and will flow much readily through a filter membrane or a fine glas frit, or alternatively a filter bed filed with fine sand, sealite etc. Using this technique you are probably able to filter with a much smaller pore size. I would advice against CCl4, benzene or dichloromethane, because they are cancerogenic and toxic and not safely handled outside a lab setting with proper fumehoods and air exchange system.

Answer 2

I'm not sure how to induce agglomeration of the burnt particles to speed up their sedimentation. I'd try one or both of the following:

1. Maintain the wax in its molten state longer without stirring, then scrape off the particulate-rich layer.
2. Melt the wax in hot water, hoping the particles selectively disperse into the water rather than staying in the wax.

Answer 3

The dark color in beeswax is likely due to two distinct materials: #1. soot (i.e., particulate matter, including partially burnt wicks) and #2. dissolved matter, essentially dark colored molecules (of undetermined, but very large molecular weight).

Removal of the larger particulates by filtration may not improve the color sufficiently. Removal of the residual very small particles and high molecular weight materials could be improved by using a filter bed of granular carbon/charcoal to adsorb them.

Selection of the filter material will be a time-consuming experimental journey. There are many carbons on the internet. Some things to consider:

1. Activated carbon for aquariums is likely to be tiny-particle-free, and colorless

2. You could wash the carbon to remove color by using water, alcohol, or petroleum solvents. Dry the carbon before using it with the beeswax.

3. Large particles could be crushed to give more surface area for adsorbing the beeswax impurities, but might produce tiny particles that go thru the filter

4. A long tube of coarse particles could be equivalent to a fine filter paper, but would need only a coarse screen to hold the carbon (i.e., a chromatography column or column filtration).

5. The chromatography column shown would allow you to discard the darkened filter material, but if you are using black carbon to remove dark colored material (ironic, isn't it?), this will not be possible. Just keep using the same column till the output beeswax isn't light enough, then toss the column and continue with a new batch of carbon filter material.

Answer 4

I made a comment about zone purification that seems to have been ignored. If the fine particles are actually denser and do settle with gravity a vertical zone purification setup might hasten the separation. It could be tested on a small scale using a glass or plastic cylinder and a heating tape to see if the particles settled and were aided by the progressive melting and solidification of the wax. It is explained exhaustingly in Wikipedia https://en.wikipedia.org/wiki/Zone_melting#High-resistivity_devices

Answer 5

The first thought was to add $\ce{BaTiO3}$ powder, melt, and mix. My understanding is, carbon is a polarizable solid and $\ce{BaTiO3}$ is ferroelectric and is also much heavier, so it might bind to carbon particles and sink to the bottom. Later I would reuse the $\ce{BaTiO3}$ powder if carbon can be removed by burning it.

Care must be taken not to breathe the dust.

I never tried it myself, I don't even have any beeswax, just an idea.

Answer 6

I think I have a test for zone purification. Fill a narrow cylindrical glass jar [similar to what salad olives come in] with molten wax. Place the covered jar in water heated just above the melting point, insulate the jar bottom so the jar bottom is not touching the bottom of the pot. Allow the water to evaporate slowly so that the wax in the immersed jar is molten and the wax in the exposed jar crystallizes. This will require some effort. Eventually the front will move down the jar leaving pure wax on top if it works. This relies on Brownian movement and gravity both free with no moving parts. It works for the Arctic Ocean ice that freezes from the top down. If it does not work too bad not much lost. If it does work I see one problem it might also separate wax molecules by weight a type of size exclusion. I see no problem with scaleing up: a taller pot, a taller tube and some more time.