My wastewater sample consists of lot of impurities and particulate matter. Therefore, when I add hexane for the seperation of oil and grease from water, it will form a very large emulsion. Even centrifuging the sample wont seperate the layers clearly. I've used alchohol for the emulsion breaking and it lead the sample to clearly seperate the sample into four layers after centrifuging at 2400 rpm for 5 minutes. Bottom layer : water and alchohol phase, Next later : Blackish solid like layer, Next layer : White solid like layer, Top layer : Hexane and oil.
Please let me know whether this modification is correct.
Kind regards, Kasun Samarasiri
Kasun I'd be concerned that some of the O&G will end up in the ethanol.
Have you tried (1) acidifying the sample to pH 2 with HCl, or (2) adding NaCl prior to hexane addition?
And have you tried agitating the separating funnel less aggressively, by holding it horizontally and rotating it so the phases swirl together? This can take longer but may result in much reduced emulsion formation.
You can also try filtering through glass wool after the extraction step.
Thank you Mike for your prompt response. Yeah, I've acidified the sample (1) and mixed it well. Anyway, I will try the second step mentioned by you at my university laboratory. Yes, I do filter the sample using a filterpaper filled with anhydrous sodium sulphate. Any other suggestions by yourself on this matter is kindly appreciated.
Thank you!
Kasun,
you should use polyelectrolytes, which will bond to the droplets of organic/oil phase. You should know the charge of the oil droplets. Probably it will be negative - in such case cationic (having positive charge in the solution) polyelectrolytes/demulsifier should be used.
At proper concentration - normally 50-500 ppm (of demulsifier in water phase) the organic phase will separate. A mixing and/or gas flotation can be helpful.
regards,
G
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