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Manufacturing a super-active carbon using fast pyrolysis char from biomass and correlation study on structural features and phenol adsorption

Hwang, Hyewon, Sahin, Olga, Choi, Joon Weon
RSC advances 2017 v.7 no.67 pp. 42192-42202
BTEX (benzene, toluene, ethylbenzene, xylene), Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, activated carbon, active sites, adsorbents, adsorption, biomass, biorefining, biosorbents, catalysts, coproducts, manufacturing, mass transfer, nanopores, phenol, porosity, potassium hydroxide, pyrolysis, surface area, weight loss
Fast pyrolysis char, obtained from two biomasses at 500 °C with a residence time of 1.3 s, was used as a precursor of nanoporous carbon material under different KOH loadings. In order to investigate a potential application as a biosorbent, a phenol removal test according to contact time and initial adsorbate concentration was also conducted in this study. During the process, a significant change in bonding structure of char focusing on weight loss and released volatiles was observed. In the presence of catalyst, aromatic hydrocarbons including BTEX were significantly released along with intermolecular bonding cleavage. After KOH activation at 700 °C for 2 h, the produced carbon material was characterized by van Krevelen diagrams, XRD, Raman spectroscopy, and XPS analysis. The produced activated carbon has a highly aromatic structure compared with commercial activated carbon (AC). In addition, a super-active carbon with a large pore volume (1.58 cm³ g⁻¹) and high specific surface area (2711 m² g⁻¹) was successfully prepared, and the pore size largely depended on catalyst loading. Furthermore, the Langmuir adsorption capacity of the produced activated carbon for phenol was 625 mg g⁻¹, which is superior to that of AC (500 mg g⁻¹). Interestingly, a correlation study revealed that mesopore volume has a strong positive correlation with adsorption capacity, probably due to an increase in mass transfer and active site accessibility. This work suggests the possibility of developing green carbon materials using a co-product of the biorefinery process as a natural adsorbent that exceeds the performance of AC and also expands insights into their thermal conversion behavior during the process.