Mesoporous activated carbon yielded from pre‑leached cassava peels
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Date
2021
Journal Title
Journal ISSN
Volume Title
Publisher
Bioresources and Bioprocessing
Abstract
The search for alternatives to fossil-based commercial activated carbon (AC) continues to reveal new eco-friendly
potential precursors, among which is agricultural waste. The key research aspect in all these endeavors is empirical
ascertainment of the core properties of the resultant AC to suit a particular purpose. These properties include:
yield, surface area, pore volume, and the active surface groups. It is therefore pertinent to have process conditions
controlled and tailored towards these properties for the required resultant AC. Pre-leaching cassava peels with NaOH
followed by KOH activation and carbonization at holding temperatures (780 °C) above the melting point of K (760 °C)
yielded mesoporous activated carbon with the highest surface area ever reported for cassava peel-based AC. The carbonization
temperatures were between 480 and 780 °C in an activation–carbonization stepwise process using KOH as
the activator at a KOH:peel ratio of 5:2 (mass basis). A 42% maximum yield of AC was realized along with a total pore
volume of 0.756 cm3g−
1 and BET surface area of 1684 m2g−
1. The AC was dominantly microporous for carbonization
temperatures below 780 °C, but a remarkable increase in mesopore volume (0.471 cm3g−
1) relative to the micropore
volume (0.281 cm3g−
1) was observed at 780 °C. The Fourier transform infrared (FTIR) spectroscopy for the pre-treated
cassava peels showed distortion in the C–H bonding depicting possible elaboration of more lignin from cellulose
disruption by NaOH. A carboxylate stretch was also observed owing to the reaction of Na+
ions with the carboxyl
group in the raw peels. FTIR showed possible absorption bands for the AC between 1425 and 1712 cm−
1 wave
numbers. Besides the botanical qualities of the cassava peel genotype used, pre-leaching the peels and also increasing
holding activation temperature above the boiling point of potassium enabled the modified process of producing
highly porous AC from cassava peel. The scanning electron microscope (SEM) and transmission electron microscope
(TEM) imaging showed well-developed hexagonal pores in the resultant AC and intercalated K profile in the carbon
matrices, respectively.
Description
Keywords
Activated carbon, Cassava peel, Pre-leaching, FTIR, Surface area and pore volume
Citation
Kayiwa, R., Kasedde, H., Lubwama, M., & Kirabira, J. B. (2021). Mesoporous activated carbon yielded from pre-leached cassava peels. Bioresources and Bioprocessing, 8(1), 1-12. https://doi.org/10.1186/s40643-021-00407-0