(2018) Journal of CO₂ Utilization_Contribution of pyrolytic gas medium to the fabrication of co-impregnated biochar

Cho D.-W., Kim S., Tsang D.C.W., Bolan N.S., Kim T., Kwon E.E., Ok Y.S., Song H.

(Elsevier Ltd) Journal of CO2 Utilization ISSN: 22129820 Vol.26 Issue. Article No. DOI: 10.1016/j.jcou.2018.06.003

Co-impregnated biochars were fabricated by pyrolysis of spent coffee grounds (SCG) or glucose as carbon (C) sources under N₂ and CO₂. The formed biochar samples were characterized with FE-SEM, TEM/EDS, XRD, TGA, Raman, XPS, and BET, and further used as catalytic medium for the reduction of p-nitrophenol in the presence of NaBH₄. The physicochemical characteristics of biochar significantly changed with the types of C precursor and flow gas stream. The biochar from pyrolysis of SCG under N₂ gas stream showed good dispersion of Co nanoparticles (10-20 nm) in carbon matrix as compared to that produced under CO₂ stream, but BET surface area was very small (4.5 m² g^-1) due to pore blockage by thermal degradation products. SCG-derived biochar formed in the presence of CO₂ possessed highly porous structure due to CO₂-assisted C volatilization. In contrast, for glucose-derived biochar, significant reduction in porosity of biochar occurred with excess devolatilization of C under CO₂ conditions, while the pyrolysis under N₂ flow produced porous biochar. These contrasting results demonstrated the significance of structure crystallinity and thermal degradability of C precursors. The catalytic performance of biochar was better correlated with the external surface area rather than microporosity. © 2018 Published by Elsevier Ltd.

This work was supported by Korea Ministry of Environment (MOE) through Waste to Energy Recycling Human Resource development Project.