Adsorption-diffusion of trace organics in Baijiu on porous Fe2O3

Abstract

Fe₂O₃ is the most abundant metal oxide in pottery jars after silicon and aluminum oxides, playing a crucial catalytic role in the transformation of flavor compounds during the aging of Baijiu. In this study, three porous Fe₂O₃ samples (S1, S2, and S3) with varying nano/micron particle ratios were prepared, exhibiting specific surface areas of 3.18, 3.62, and 3.49 m². g⁻¹ and average pore sizes of 11.70, 13.16, and 25.92 nm, respectively. Adsorption kinetic experiments revealed that S3 achieved the highest equilibrium adsorption capacity (16.29 mg/g), with the pseudo-second-order model (R² > 0.999) confirming chemisorption as the dominant mechanism. GC-MS analysis demonstrated that Fe₂O₃ exhibits weak adsorption of esters (e.g., ethyl acetate, with a post-adsorption concentration of only 2.53 mg/L) but selective adsorption of aldehydes and alcohols (e.g., 3-furfural and dimethylsilanediol), potentially facilitating oxidation and hydrolysis reactions. Molecular dynamics simulations indicated significantly higher diffusion rates for water (diffusion coefficient: 2.61 × 10⁻⁷ m²/s) and ethanol in 25 Å pores compared to 35 Å pores, suggesting that smaller pores enhance molecular migration and surface catalysis.