Biochar as a Structure-Tunable Stationary Phase for Column Chromatographic Fractionation of Bio-Oil

The complex composition of bio-oil necessitates advanced separation strategies for its valorization. This work reports the application of biochar as a sustainable and structure-tunable stationary phase in column chromatography for the efficient fractionation of bio-oil. Biochars with distinctly different properties were engineered through pyrolysis of bamboo at 400 °C (bsC-400) and 700 °C (bsC-700). Comprehensive characterization confirmed that bsC-700 possessed a highly aromatized and hydrophobic surface with a well-developed porous network, while bsC-400 retained a polar and oxygen-functionalized surface. Their chromatographic performance revealed a fundamental structure-function relationship, as evidenced by the strong retention of sugars on the polar surface of bsC-400 via hydrogen-bonding interactions, which necessitated the use of aggressive solvents for elution. In contrast, bsC-700 exhibited exceptional affinity for phenolics via π-π stacking, while facilitating the early and efficient elution of sugars with moderately polar solvents due to its non-polar chemistry. This study establishes pyrolysis temperature as a critical design parameter for tailoring biochar selectivity, positioning it as a versatile stationary phase for targeting specific compound families within complex mixtures and advancing integrated biorefinery concepts.