The use of biochar as a green catalyst support is emerging as high-end applications beyond soil remediation, including pollutant degradation and chemical/biofuel synthesis. They show varying significance depending on the catalytic sites on biochar, which may be controlled via novel pre-/post-synthesis modifications. A few examples are discussed in detail. An engineered biochar was fabricated via paper mill sludge pyrolysis under CO2 atmosphere, and its adsorption capability for As(V) and Cd(II) in aqueous solution was evaluated in a batch mode. The characterization results revealed that the biochar had the structure of complex aggregates containing solid minerals (FeO, Fe3O4 and CaCO3) and graphitic carbon. The adsorption of As(V) and Cd(II) reached apparent equilibrium at 180 min, and followed the pseudo-second-order kinetics. A novel nitrogen-doped biochar embedded with cobalt (Co-NB) was fabricated via pyrolysis of glucose pretreated with melamine (N donor) and Co(II). The Co-NB showed hierarchical porous structure with well-dispersed Co nanoparticles (20-60 nm) on the graphitic biochar surface. The Co-NB showed higher p-nitrophenol (PNP) reduction into p-aminophenol (PAP) by NaBH4 than Co-biochar, achieving 94.3% removal within 4 min. Co-NB catalysts were further fabricated by pyrolysis of spent coffee grounds (SCG) and glucose as carbon (C) sources under N2 and CO2 atmospheres. SCG-derived biochar generated in the presence of CO2 gas stream possessed highly porous structure due to CO2-assisted C volatilization via the Boudouard reaction. In contrast, for glucose-derived biochar, significant reduction in porosity of biochar occurred with excess C burn-off under CO2 flow stream, while the pyrolysis under N2 flow produced porous biochar. These contrasting results demonstrated the significance of structure crystallinity and thermal degradability of C precursors. This elucidates the links among catalytic performances and physicochemical properties, illustrating the potential of engineered/designer biochar catalyst in the future.

Engineered biochar for contaminant adsorption and reduction

256th National Meeting (2018)

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