Dear all,

I have just found a paper concerning BET and particle size. It seems that we can not get particle size distribution with BET, but at least we can get the average particle size (assuming that the particle is spherical and non-porous) by using BET. Here is the relation:

SSA (BET) = 6/(rho.D)

Where SSA [m2/g] is the specific surface area measured by BET, rho is density of particle, and D is the particle diameter.

Following is the paper:

http://www.google.co.jp/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&ved=0CCYQFjAA&url=http%3A%2F%2Fwww.intertek.com%2Fpharmaceutical-physical-characterization-surface-area-porosity%2F&ei=o8KNUpngDcTHkwWa14H4Aw&usg=AFQjCNFl0c64Wb8-bL1ZbpzDfgTYyWcRdw&bvm=bv.56988011,d.dGI

Regards

No, you can not use BET for particle size distribution.

Scanning Mobility Particle Sizer (SMPS) has been used in order to measure the particle size distribution in range of few nanometer to 850 nm. There is access to other techniques such as APS if you need to measure particle size distribution in the range of 1 micron to 10 micron. I refere to my publications list i RG with regard to physical characterisation of particulate.

Dear Sanati,

Thank you very much for your answer!

Dear Son,

BET is only a method to determine the surface area from nitrogen adsoption isotherm, most of times. If the solid you are measuring is non porous and particles are spherical you can calculate an average particle size as long as you know / determine the real density of the solid by helium pycnometry.

Thank you very much, Vanessa!

BET is very useful in connection with other particles size measurement techniques which assume a particle shape. By comparing BET surface with that calculated from PSD you get more insight into your particle nature.

for an adsorbent (agriculture wastes) can we take particle size through particle size analyzer?

Of course, however, the useful device will depend on the characteristic range to be determined.

Thankyou sir

Vanessa Fierro thanks for good and informative reply.

I have a BET report which also gives average particle sizes in nanometers, there seem to be a relationship.

Thank you sir

Does the sample's particle size affects the BET surface area?

do a calculation for dependence of surface area on particle size to find out.

I will rather suggest zetasizer measurement for particle size distribution.

I also have BET reports which also gived average particle sizes in nanometers, I eager to know how they are calculated?

For this calculation you assume that particles can be considered as spheres. The smaller the spheres the larger their specific surface area. In case of particles with open pores this will give to much smaller diameter to compensate for the assumption of nonporous particles.

In case if particles are non-porous then you can apply a simple calculation knowing materials density, SBET and shape-factor: for isotropic bodies (spheres, cubes) it is 6; for fibers or needles - 4; for planar particles (plates, films) - 2.

Son Thanh Nguyen

The relation is simple: SSA = 6/(D[3,2]*density)

Using the units of m2/g for BET, density in g/cm3 gives the Sauter Mean Diameter, D[3,2] in microns. See attached.