Dear Suresh,

The measurement of iodine number can be used to roughly estimate the surface area of activated carbon at room temperature conditions.The principle is very similar to BET surface area determination.You can search internet and find standard methods for iodine number determination for activated carbon. Go through the attachment you will get a clear idea. Also "Surface Area of Activated Carbon Determined by the Iodine Adsorption Number" by A. Mianowskia et.al (DOI:

10.1080/00908310500430901)

Dear prince,

Thanks for your time and guidance... 

Sureshkumar,

Iodine number is a measure of the equilibrium mass of iodine adsorbed on a surface from excess. It is a standard test method.

In adsorption theory, molecules of different sizes/functionality will be correspondingly physically adsorbed at surface sites of different energies. Chemists use different molecules to gauge and model adsorption in an analogical manner. Since iodine is quite small, it can be a good indicator of the capacity an activated carbon has available in very small/high energy pores. In reality it only corresponds to the carbon's equilibrium capacity for iodine, but increasing iodine number correlates to increasing porosity and it is used as a general performance metric.

Dear Martin,

Thanks for your time and consideration

What is Iodine number?

Iodine number is a widely used parameter for activated carbon testing for its simplicity and a rapid assessment of adsorbent quality. It gives an estimate of its surface area and porosity The iodine number is defined as the milligrams of iodine adsorbed by one gram of material when the iodine residual concentration of the filtrate is 0.02N (0.01 mol L-1) according to ASTM D4607 standard, which is based on a three-point isotherm.

How to measure it?

The sample is treated with 10mL of 5% (V/V) HCl. The mixture is boiled for 30 s and then cooled at room temperature. 100mL of 0.1N iodine solution is immediately added to the mixture and stirred for 30 s. The solution is then filtered and 50mL of the filtrate is titrated with 0.1N (0.05 mol L-1) sodium thiosulphate solution using thyodene (or starch) as an indicator. The amount of iodine adsorbed per gram of adsorbent is plotted against the residual iodine concentration, using logarithmic axes. If the residual iodine concentration is not within the range (0.008–0.04 N), the procedure is repeated using different carbon masses for each isotherm point. A regression analysis is applied to the three points and the iodine number is calculated as the amount adsorbed at a residual iodine concentration of 0.02 N.

I hope all these information will be helpfull

I agree with you Khaled. The  "standard method at ASTM D4607" shows the experimental part of iodine number determination. But it does not explain the Iodine number it self.

Well, Iodine number is used to determine the porosity of an AC especialy the microporsity since le size of iodinemolecule is small and can easily reach the micropores.

Dear Bestani and khaled

Thanks for you informations... it is informative

Stirring for 30 seconds might not give standard results. Try stirring for 5 minutes at 1400-1500 RPM. Additionally, ASTM D4607 is no longer the latest Version to perform Iodine Number test.

Dear Prasad,

Please what is the recent standard to determine the iodine number?

Thank you.

Dear All, Thank you for the detailed answer on determination of Iodine number.

After calculating iodine number, how to calculate microporosity?

For more information about the relationship between the iodine number and the microporosity, check this reference:

Noszko, L., Bota, A., Simay, A., Nagy, L., 1984. Preparation of activated carbon from the byproducts of agricultural Industry.  Periodica Polytechnica. Chem. Eng. 28, 293-297.

Thank you

Dear Sir, I studied this reference. It mentions about how Iodine adsorbed (mg/ kg) relates to surface area. I am not yet clear how it relates to porosity properties

The reference mentioned herein is not available here. Could you give the detailed procedure to find iodine number of activated carbon?

Simply:

iodine number characterizes the micro porosity of activated carbon (gas char coal) and shall have minimum 950 mg/g.

Higher is better. - Lower worse.

regards

The iodine number is mass of iodine in g that is consumed by 100 g of a chemical substance. Iodine numbers are often used to determine the amount of unsaturation in fatty acids. This unsaturation is in the form of double bonds, which react with iodine compounds. The higher the iodine number, the more C=C bonds, th methods for the determination of iodine value are

Huebl's iodine

H. P. Kaufmann

Please, explain me what does it mean residual concentration of the filtrate? I don't get this. Thank you!

ASTM D-4607 method is attached below.. I hope this will help

It didn't help because there is no explanation what the residual concentration is about. Is it all filtrate that's been filtrated into the flask or only a portion of 50 ml that's been titrated by thiosulfate? Additionaly, it's weird that iodine concentration fluctuates when I change the mass of activated carbon. Does anybody have the same problem?

ASTM - D 4607 – 94 (Reapproved 1999)

Bestani Benaouda sir i need a clarification...

1.what are all the parameters changed while activation process (steam activated) for increasing CTC level.

2. Need to increase moisture level from 2% to 8% (25g of AC) pls suggest how much amount of water is to be add.. Any calculations is there

What is iodine number in terms of activated carbon? What are the effect of iodine number on activate carbon porosity ?

The iodine number is defined as the milligrams of iodine adsorbed by 1.0 g of carbon when the iodine concentration of the filtrate is 0.02 N . The iodine number is determined according to the ASTM D4607-94 method .

this would be good reference

pls share ASTM - D 4607 – 94 (Reapproved 1999)

How iodine value is related to porosity?

Is iodine number is applied for all types of adsorbent

As far as I'm concerned, Iodine number is a specific parameter for activated carbon ONLY