Riverstones Biodiesel Emulsion Busting

Emulsion Busting

Here is a method for breaking emulsions that Jack Jones stumbled upon in late 2004. This method uses biodiesel glycerin by-product as the emulsion breaking ingredient, a readily available ingredient for anybody that makes biodiesel. Research continues on the active ingredients in the by-product, stay tuned.

Biodiesel emulsions sometimes occur during the wash phase. This can occur for several reasons relating to unreacted oils, poorly separated biodiesel/by-product, etc. However, all these situations have one thing in common; aggressively washing biodiesel in the presents of water and soap. Soap molecules (a by-product of the biodiesel reaction created when free fatty acids are neutralized with the catalysts) are long chain molecules that have one end that is attracted to polar molecules (such as water) and the other end that is attracted to nonpolar molecules (such as dirt, grease, biodiesel, etc.). These long molecules will attach themselves to dirt, grease, biodiesel, etc. and then bunch together forming a "bubble" around the dirt, grease, or biodiesel so that the ends of the soap molecules that are attracted to water form the outside surface of a sphere with the dirt, grease, or biodiesel at the center of the "bubble".

Emulsions occur during aggressive biodiesel washing because the biodiesel becomes "imprisoned" in these soap spheres. These soap spheres can be broken apart by pushing them tightly together by freezing the whole emulsion. Or we can break the emulsion by lowering the surface tension between the soap molecules using a solvent like alcohol. The alcohols (methanol and glycerin) in the biodiesel by-product are a readily available solvent to break emulsions; much easier than freezing a large emulsion solid.

This page provides a pictorial walk-through for creating and breaking a small biodiesel emulsion. We start with clean biodiesel. Since clean biodiesel will not emulsify with water alone we must also add soap to the biodiesel. The soap we add is, ironically enough, provided by biodiesel by-product. With the combination of clean biodiesel, soap (biodiesel by-product), water, and a very aggressive mixing of the liquids we easily create a biodiesel emulsion.

With the biodiesel emulsion created we then break the emulsion by adding the solvents (the biodiesel by-product). We add small amounts of the by-product to determine how much is really needed to break our emulsion. It is important not to mix these solvents too aggressively or their emulsion breaking power will be halted by the emulsion creating power of the soap that is present. A thorough mixing is all that is needed. It is also important to have the mixture a little warm at this point. We heated the mixture up to 90F.

In in discussion at infopop the following ideas as to why this method works were put forward:

From Mesuno

My final year research project at university involved producing liposomes containing water droplets, very much like happens in emulsion formation although using a chemical rather than mechanical method of producing them.
We had various ways of bursting them:- Physically by sonification or repeated freeze/thaw cycles or chemically by either

changing the osmotic balance around the droplets

introducing surfactants to disrupt the membranes.

At a guess I would say that both of the above mechanisms are involved in the glycerine emulsion busting method. Predominantly though it will be the increase in ionic molecules disrupting the soap membranes. You can keep adding it for a while but eventually there just isn't enough free soap left to maintain the liposomes.

From tupper

why adding glycerine works:
my guess--and i am a chemist, though this is far from my area of study--is the the adding glycerine increases the specific gravity of aqueous layer and thus provides more driving force for phase seperation. (s.g. of glyc is like 1.2) also, all the NaoH or KOH that you add to get the raction going ends up in the glycerine, so the glycerine ought to have a high ionic strength. so adding glycerine to the emulsion is a lot like adding salt to an emulsion....