Narrow pore size distribution biochar derived from distiller's grain wastes for gasoline vapor adsorption: Porous structure formation mechanism and structure-property relationship

The control of vehicle evaporative emissions has become increasingly critical, as they represent a significant source of atmospheric pollution. Activated carbon used in canisters serves as the key material for managing these emissions. However, research on the structure-property relationship between activated carbon pore structure and gasoline vapor adsorption performance remains insufficient. To address this, this work proposes a “waste control by waste” strategy, using distiller's grains (DG) from Baijiu production to produce biochar with a narrow pore size distribution for efficient gasoline vapor adsorption. The effects of activating agent ratio, activation atmosphere, and post-treatment (desiliconization) on pore structure were systematically investigated. By combining online analysis of evolved gases during activation with multiple characterization methods, the pore structure formation mechanism of DG-based biochar was elucidated. Among these activation factors, the activating agent H 3 PO 4 acts as a dehydrating agent and a cross-linking promoter, inhibiting biomass pyrolysis and creating pores. Oxygen in the activation atmosphere helps form microporous structures. The post-treatment, desiliconization process, tailored etches Si and creates controlled 1–2 nm pores. Furthermore, through adsorption experiments at varying n-butane (gasoline vapor substitute) concentrations, the correlation between pore structure and adsorption performance was clarified. Notably, this work challenges the conventional understanding of the optimal pore size for VOC adsorption, which is regarded as 1.5–3 times the adsorbate kinetic diameter. The novel pore-concentration dependency is put forward. The optimal sample (1.75DGP-Air) demonstrated high adsorption capacity, low isosteric adsorption heat, and excellent cycling stability, providing both theoretical and practical guidance for developing high-performance gasoline vapor adsorption materials.