Biochar is rather complicated what comes to porosity. There are wide range of pores from subnanosize to tens of micrometers. This makes determination of total porosity challenging. What are current techniques to overcome this challenge particularly in case of large macro pores (tens of micrometers)? What would you consider best? How do you see comparison of results to N2 and CO2 sorption when using this technique?
You can find the information about the different types of indentify of porous solids in the exellent "Handbook of Porous Solids" Edited by Ferds Schuth, Kensis and Jens Weit Kamp, WILEY-VHC, 2002.
Good reading, Taras
Just a quick initial answer:
You can use Mercury porosimetry.
This technique covers pore sizes between about 300 to 500 micrometer down to 3.5 nm. I have used it with wood samples.
See the following two papers.
There are also publications on the comparison between N2 adsorption and Hg-porosimetry. I added a 3rd paper on that topic below.
Indeed, you can use Hg porosimetry or just electron microscooy: SEM and TEM
Thank you everyone for your effort! There appears to be several opportunities however, Hg porosimetry is very well known technique so it would be a wise choice.
SEM and TEM techniques for porosity analysis seems to be a bit rare.I would be interested to know how reliable pore volumes one can calculate using them?
All of the techniques have advantages and disadvantages.
I like TEM or SEM because you "see" the pores. You will get an idea of where they are, what shape they have and just get a more detailed picture.
Mercury porosimetry will give you average numbers for pore size and calculate the pore volume. It works over a very large range and that it its most significant advantage. The most critical disadvantage is the fact that it will give you the pore size based on the "largest connected entrance to a pore". For example: if you have a 10 micrometer pore, which is only accessible through 1 micrometer connections from the outside, then this pore (pore volume) will be shown/counted as a 1 micrometer pore.
In conclusion, you should always use as many different techniques as possible and then combine their answers.
Herbert Giesche, you are absolutely right. Every technique has advantages and disadvantages. Furthermore, I agree with you that it would be great to use as many techniques as possible. However, one does not always have that luxory. I am looking for a technique which can cover a very large pore size range and therefore Mercury porosimetry would be a good choice in here.
Yes, this is certainly correct and I am personally very much in favor of Hg-porosimetry, but I also know that handling of mercury is restricted in many institutions and as such Hg-porosimetry might not be available.
In case you don't have access, send me an e-mail and I could certainly run a couple of tests for you.
Dear Alatalo
GOOD Luck for your project.
Look, its very common and useful technique to do N2-adsorption surface area analyses of your materials. Not only, the surface area but pore size distribution and pore volume can also be obtained via this technique. Besides, SEM and TEM can also help you doing so.
- Badges
- Science topic
- Similar topics
- Physical Sciences
- Materials Science
- Materials
- Inorganic Materials
- Ceramics
- Glass