Public Lab Research note

Separating Oil from Water by Freezing the Water Part 2

by Matej | December 15, 2015 18:34 15 Dec 18:34 | #12520 | #12520

This note is an extension of my previous note "Separating Oil from Water by Freezing the Water" that could be found here.

What I want to do

In general I am attempting to separate oil and water by freezing. This research note is a new addition to that. In particular I was testing two things: 1. How much oil can I recover from water each time if I re-freeze the oil/water (OW) mixture repeatedly? 2. Does the repetition of this process changes the oil spectra?

My attempt and results

  1. Initially I was thinking to repeat the freeze / defrost / collect cycle as many times as possible, but as it turned out only one extra cycle produced enough recovered product oil to collect without using a cotton swab method (this collection method requires mixing the spec with mineral oil. I am trying to avoid mineral oil, since it slightly changes the measured spectra).

I was able to recover various amounts for different kinds of oils. I assume this is mainly due to two factors: viscosity, and the amount already recovered before this particular collection cycle. For example the 5W30 oil is quite viscose and if cold, doesn't collects well (doesn't flow or drips well). This particular oil also changes color from transparent honey to milky white. More info on that in separate note here. On the other hand the much lower ConEd Dielectric Fluid was not possible to recover because I recovered most of the of the product in the first collection cycle before.

Here are the amounts of oils per oil/water mixture (OW ratio 1:20) I was able to recover in the second cycle:

5W30: 4 drops Crude North Dakota: 6 drops ConEd Dielectric Fluid: 0 drops 20W50: 6 drops 80W90: 5 drops

One very important note on how NOT to drip melted ice water into your sample: Leave your frozen sample in the fridge at all time. Take it out only when collecting the sample. Do not hold the frozen sample with your bare hand, because it will start melting very quick. Even if you are not holding the sample with a bare hand, water will start melting approximately in 1 minute in a room temperature. That said, you have to collect all the oil you can within 1 min.

here are some measured spectra that Spectral workbench produced a match: Crude recovered Cycle 1:

Crude recovered Cycle 2:

Crude Oils Compared:

80W90 recovered: Did not matched spectra from the 1st cycle.

Questions and next steps

Next steps will be to better compare the measured spectra and update the note.

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.


Cool, Matej! Do you have comparison sets of the pure unfrozen/undiluted samples alongside the frozen versions, and also alongside samples in mineral oil? I'm also curious about your statement that mineral oil will change the spectrum, can you cite your reference? Was it @ethanbass's work? Just interested in interlinking all this great research. Thanks!

Also, when do you plan to try collecting a sheen from the surface of a body of water in the field? Just curious, thanks!

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Hi Jeff. I took triplicate spectra of each oil, before mixing it with water and after recovering the oil from frozen water. You can find them at my spectral workbench. Their title is in this format: myInninitals_OS_oilName_IN... for initial sample (MV_OS_05W30_IN...) or myInninitals_OS_oilName_PO... for recovered product sample (MV_OS_05W30_PO...). I am about to take also triplicate spectra of the oil water mixture before freezing very soon. With Gretchen we decided that I won't be using mineral oil for my samples. - At the Barnraising's OTK session @ethanbass mentioned that certain dilution of Oil products mixed with mineral oil do shift the spectra. Specifically lower dilutions. @ethanbass is working right now on incremental dilution tests to identify the shift. I was thinking to do the same thing and compare, but I think we would probably need some at least semi-precise pipettes to do that. Otherwise if you are using drops or eyedropper you will end up with huge increments after couple of addition. I discussed that with Gretchen too. Will see maybe I'll ask my lab to donate me some old pipettes if they don't need them anymore.

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Cool; i mentioned isopropyl alcohol as a possible evaporate-able solvent in the comments on

Thanks! Looking forward to seeing @ethanbass's tests!

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