What is the significance of the iodine value of activated carbon?

Release time:

25-11-05

Source:

he iodine value is a measure of the equilibrium mass of excess iodine adsorbed on the surface of activated carbon. This is a standard testing method.

In adsorption theory, molecules of different sizes/functionalities will correspondingly physically adsorb at surface sites of different energies. Chemists measure and model adsorption in similar ways using different molecules. Since iodine is very small, it is a good indicator of the availability of activated carbon in very small/high density pores. The iodine number corresponds to the iodine balancing capacity of the activated carbon, and the amount of adsorbed iodine is related to the increased porosity of the activated carbon and is used as a general performance indicator.

What is iodine value?

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

How to measure?

v Treat the sample with 10 mL of 5% (V/V) HCl. Boil the mixture for 30 seconds and then let cool to room temperature. Immediately add 100 mL of 0.1 N iodine solution to the mixture and stir for 30 seconds. Then filter the solution, and titrate 50 mL of the filtrate with 0.1N (0.05 mol L-1) sodium thiosulfate solution, using methanium (or starch) as an indicator. The amount of iodine adsorbed per gram of adsorbent was plotted against the residual iodine concentration using a logarithmic axis. If the residual iodine concentration is not within the range (0.008-0.04N), repeat the process using different carbon masses for each isotherm point. Regression analysis was performed on three points, and the iodine value was calculated as the adsorption amount when the residual iodine concentration was 0.02N.