Biochar from saw dust is saturated by passing carbon dioxide over it. Then that char is subjected to high alkaline environment ( calcium/potassium hydroxide). SEM images show many pores in the biochar in the size range of 5-10 micron which is not found in the original char ( just after production). How can this be explained?
It sounds like the CO2 treatment is at room temperature. Is there a reason for doing this? If not I suggest you test the effect of omitting the CO2 treatment as it seems unlikely to have an appreciable effect in the face of a large amount of concentrated alkali.
Thanks for your reply Dr, Milham. Yes, I have tried without CO2 saturation as well. The pore structure of unsaturated biochar does not seem to change when treated with alkali. Only change in porosity was observed when CO2 saturated biochar was immersed in alkali for over 1 week.
This is just a supposition, but it may be that non- CO2 exchanged pores in the fresh biochar are not able to be wetted by the alkali (i.e. air is largely N2 and relatively insoluble in the alkali). The role of the alkali then is in removing surface organics or ash components that are otherwise clogging the pores. And the CO2 in the pores is able to dissolve by reacting with the alkali.An equally possible method would be touse anhydrous NH3 to exchange the air and then use water to flood and wash out pores. These gases are of course rather different molecular arrangements and molecular sizes, so it could be interesting based on the hypothesis offered.
- Badges
- Science topic
- Similar topics
- Linguistics
- Composition Studies
- Publication