Most biochars have alkaline pH (above 8). That could be explained by Ca, Mg, K oxides released during the charring process (pyrolysis). Yet, some biochars have acidic pH (less than 6). What may be responsible for such a low pH?
Dear Dr N. Hue,
During the course of my experiments, I also observed that the pH of some bicohars were around 6. Though weakly acidic it deviates from the trend observed in literature. That said, I noticed the acidic pH was for biochars produced at lower temperatures, which were incidentally where I also observed high liquid products. As such, the plausible inference may be due to residual acidic compounds in the liquid. What are your thoughts on this?
Regards,
BBN
Biochar has more oxygen containing functional group will end up with lower PH.
Sir Nguyen Hue
Biochar produce at lower temperature 250-350 depending upon raw material have high content of oxygenated surface functional groups, leading to slight acidic pH. While, biochar made at higher temperature are alkaline in nature due to increase in ash content as well as reduction of surface functional groups.
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