Comparative study on one-step pyrolysis activation of walnut shells to biochar at different heating rates
Abdulmajid Abdullahi Shagali, Song Hu, Yankui Wang, Hanjian Li, Yi Wang, Sheng Su, Jun Xiang
Abstract
Pyrolysis of walnut shells to biochar at 700 °C using N2 gas was compared to one-step activation using steam/KOH under four different heating rates (10–40 °C/min). Steam biochars developed better surface area property of 342–556 m2/g compared to others (19–135 m2/g) over the same heating rates; meanwhile, increasing heating rate caused functional groups alteration and was distinct on the surface area property as about six-fold and two-fold difference from the lower to higher rates were recorded in neutral char and the steam/KOH activated biochars respectively. Increasing heating rate affected the neutral and steam biochars’ Raman intensity ratio whereas trivial influence was recorded on KOH-biochars.