I have a solution of water and calcium nitrate that is contaminated with some sort of heavy petroleum oil, semi-solid at room temperature a bit like petroleum jelly, and a strong odor of very crude refining. I wish to retain the salt solution and discard the oil.

The bulk of the oil has adhered to the walls of the glass beaker but a small percent remains in floating in the solution. What are some typical lab methods that could remove the remaining oil? Would adjusting pH assist the process? Would changing the temperature to solidify or melt the grease, or some cycling of temp?

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    $\begingroup$ You could attempt to wash it with a low boiling point organic solvent which is immiscible with water such as diethyl ether or hexane. Do you have a separating funnel? $\endgroup$
    – Waylander
    Apr 10, 2022 at 7:38
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    $\begingroup$ Maybe a simple filtration will do the job. I would try. $\endgroup$
    – Maurice
    Apr 10, 2022 at 8:06
  • $\begingroup$ I found that by transfering into a series of clean plastic bottles from the recycle bin the majority of grease has adhered to the bottles and the solution easy to decant, with minor rinse of distilled water for near zero loss. Solution is still a touch cloudy with very faint smell of the oil, it is now just barely "good enough" but I may try the non-polar solvent wash just to see if it improves, would certainly be handy for larger quantities. (Using as fertilizer supplement. Issue is caused by current supply chain for economical grades. Likely blind repack of untested lowest bidder import.) $\endgroup$
    – Max Power
    Apr 10, 2022 at 18:57
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    $\begingroup$ Put it in the fridge. I'd be surprised if almost all of the oil/grease didn't fall out. Run the remaining solution through a coffee filter. Repeat the process until you're happy with the result. $\endgroup$ Apr 10, 2022 at 18:58
  • $\begingroup$ I do not have a separatory funnel at this time, but I could rig something similar as this is not a high value or difficult to work with solution so small losses can be tolerated. I also intend to setup a solvent recovery distillation soon, both for lab and garage parts washing. $\endgroup$
    – Max Power
    Apr 10, 2022 at 19:00


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