What I want to do
I attempted to extract various types of oils previously mixed with (tap) water by freezing the water. This idea is based on a fact that oil has usually lower freezing point than water so I should be able to collect the oil from the top of the ice. This technique has been already used to separate natural oils from water. Please keep in mind that all of the amounts of substances are not exact because I did not used calibrated pipettes. Also parts of some more viscose products remained attached to the walls of the eye dropper or a plastic flask.
My attempt and results
I mixed the following oils with water in ratio 1:20 (1.5ml oil to 30ml water): 5W-30 Crude ConEd Dielectric Oil Fluid 20W-50 80W-90
After that I froze the the mixtures in my freezer for one day. The Product Oils (PO) separated from the frozen Product Water (PO) on the surface in different volumes for each type of PO, probably mainly due to different viscosities of the oils (but also some other properties). Following image is showing all the recovered amounts in comparison to 1ml of clean water sample. a) 5W-30 recovered b) Crude recovered c) ConEd recovered d) 20W-50 recovered e) 80W-90 recovered w) water 1ml for comparison
In the first two attempts, a) and b) samples, I was using the eyedropper to collect the oil. After that I realized that the more viscose POs are attaching to the eyedropper walls so I stoppered using it. I poured the remaining products directly directly from the flask into the cuvettes.
Samples of Pure Initial Oil Spectra Compared and Recovered PO Spectra
I took triplicate spectra of each oil before mixing with water and after recovering the PO. Here below are some examples. You can find all spectra at https://spectralworkbench.org/profile/matej
ConEd DIelectric Fluid IN (pure)
ConEd DIelectric Fluid PO (recovered)
Questions and next steps
Next steps are as referred to in my initial research note here: http://publiclab.org/notes/Matej/11-04-2015/oil-sheen-testing
This was 1:20 ratio testing. Seems like the amount of recovered PO widely varies from awesome (approx.) 75% to not so awesome but still workable (approx.) 20% or less. In case of low amounts you might have to use the Q-tip & mineral oil method previously mentioned here and here However I did not tested the PO with mixed with mineral oil yet. I am also wondering what could be such Oil to Water ratio in an actual oil spill? This method of collecting PO is certainly working and is very accessible. However, it might be changing chemicals and spectral properties of some oils. This is still TBD, In this particular case I found major differences just in the 5W-30. Product water spectra will be also be the next step. Note: Perhaps use of "thinner" cuvettes will be more helpful in case of using less recovered PO.
Why I'm interested
I am interested to test figure out a way how to prepare best specs for the OTK and to test the ability of different different DIY techniques to separate oil from water. This is one of the methods I am trying.