4 replies to this topic

[Alaaeldin55]

Hello,

I'm making an experiment to investigate the effectiveness of electrocoagulation method in separating oil in water emuslions. And I'm looking for a simple method for analysis (measuring the concentration of crude oil in water ), I know about standard methods but since the number of experiments I'm going to run are very large , I can't afford such methods. Turbidity measurment is not an option as well.

 

My hypothesis is as follows: for each sample (oil in water emuslion) I will add equal volume of normal hexane to extract the oil but instead of perfectly separating the extract from the remaining water I will just draw a very small portion of the extract using a pippet and take it for spectroscopy analysis. A claibration curve between light absorbance and known oil concentrations is created previously (no problem with this).

Would the oil concentration in hexane (after extraction) be homogenous so the concentration in the top layer is the same as in the bottom layer of hexane.

 

Hints: I don't need to measure the exact oil in water concentration but just the degree of removal resulting from different experiments. All sample will contain dissolved solids , emulsifier molecules, and suspened solids ( mainly aluminum hydroxide).

 

Thanks in advance

 

 

 

[shantanuk100]

Hi Alaaeldin,

 

It should be homogenous if well stirred. But there's no guarantee.

I would suggest an alternative method.

 

1. Take some known volume of the mixture, say around 250 or 500 ml.

2. Use Chromatographic methods of separation, i.e Take Silica Gel granules and make a packed bed, in a small sized column, they shouldn't be very expensive.

3. Now use hexane as the solvent for elution of oil.

4. Now, once you do elution, the oil, being soluble in hexane will elute at a different rate while the water wont, because it is insoluble in hexane.

5. Now take the separated oil, and measure the volume and we know that whatever is remaining from the initial quantity would be water.

6. For checking the progress of elution you can use TLC silica gel paper.

7. This way you would also be able to measure the exact concentration of oil in water, and since you have the concentrations of oil in water now, the rest is simple enough.

 

Regards,

Shantanu

Edited by shantanuk100, 26 April 2016 - 12:03 AM.

[Alaaeldin55]

Thank you very much Shantanu,
 

But the oil concentrations i'm going to measure won't exceed 1000 ppm maximum. And how can I use the silica gel column more than once without interfernece of results from diffeent experiments.

[P.K.Rao]

Infra red techniques are fast and simple. You can do the test in  just five minutes. I have seen Japanese instruments. You can get on the web jap companies.

[shantanuk100]

Hi Alaaeldin,

 

1. Usually they are not regenerable columns even though you can remove the used chemicals from the column by purging methods , because the Silica Gel once used, starts to crack, so you cannot use the same silica gel multiple times.
But in your case, I'm assuming that your number of tests would be limited in a month, so for your purpose, you can easily get sufficient quantities of Silica Gel.

 

2. This method can be used for frequent monitoring of the Oil concentrations, in discrete intervals.

If you require continuous monitoring on a second by second basis, you could use Infrared monitors like Mr. P K Rao has suggested.

You can find more information on IR methods in the link below.

1.http://www.nicoletcz...ysis Method.pdf

2.http://www.spectrosc...150d3ad40ee5a94

3.https://www.perkinel...id-Infrared.pdf

 

Regards,

Shantanu