This poster evaluates the influence of hydrothermal carbonization (HTC) or slow pyrolysis (SP) process conditions on the formed precursor biochars to the physicochemical properties of activated carbon (AC). The activated carbon is achieved through a direct or two-step chemical method involving either hydrothermal carbonization (HTC) or slow pyrolysis (SP) and subsequent chemical activation by KOH. A theory is developed on the biochar propensity to be chemically activated based on the composition of the lignocellulosic structure. Brunauer-Emmett-Teller (BET) measurements were taken to calculate the surface area and pore size of the biochars and activated carbons. The HTC biochar produced surface areas between ~1 to 11 m2/g and a predominantly mesoporous structure. When activated, the surface area increased to a range of ~800 to 1,286 m2/g and had a significant increase in micropore and mesoporous formation. The SP biochar produced surface areas between 1 to 111 m2/g. When the SP biochar was activated, the surface area increased to a range of 300 to 1,000 m2/g and consisted predominantly of micropores. Corn stover was also directly chemically activated and achieved a surface area of 984 m2/g. X-ray photoelectron spectroscopy (XPS) elemental analysis shows that the O/C ratio for the carbon residue decreases after chemical activation for HTC biochar but remains the same for SP biochar. X-ray powder diffraction (XRD) indicates that SP biochar and all AC have broad amorphous carbon peaks, whereas the corn stover and HTC biochar have distinct cellulose crystalline peaks. Vanillin absorbent experiments were performed on the various activated carbons with up to 98% reduction shown. In general, the best absorbent for vanillin was the AC produced directly from corn stover, followed by activated carbon from HTC, and then activated carbon from slow pyrolysis.

Evaluation of the physiochemical properties of biochar and activated carbon from hydrothermal carbonization and slow pyrolysis: Implications for adsorption of vanillin

ACS Spring Meeting 2021

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