The adsorption kinetics of benzo[a]pyrene (BaP) on granular activated carbon (GAC), biochar, and Haplic Chernozem soil were investigated to elucidate the underlying mechanisms governing contaminant retention in environmental systems. Batch kinetic experiments revealed a rapid initial uptake of BaP within the first 60 minutes, during which 77–81% of the total adsorption occurred. This fast phase was attributed to the availability of high-energy surface sites and facile diffusion into macro- and mesopores of the sorbents. Subsequently, the adsorption rate slowed significantly, with only 19–23% of additional BaP being captured over the next hour, indicating the onset of intraparticle diffusion limitations.
This biphasic behavior aligns with established models of porous adsorbent dynamics. The initial stage is dominated by physical interactions such as van der Waals forces and π–π stacking between the aromatic rings of BaP and the graphitic surfaces of GAC and biochar. These interactions are particularly strong due to the high electron density in the carbon matrix, facilitating stable binding of planar polyarene molecules. As the external surface becomes saturated, the slower second phase involves the migration of BaP into narrow micropores (diameter < 2 nm), where access is restricted by steric hindrance and reduced mobility. The presence of polar functional groups on biochar may further influence this process through hydrogen bonding or dipole interactions, although these effects were secondary compared to hydrophobic and π–π interactions. Scanning electron microscopy (SEM) imaging confirmed distinct morphological differences among the materials. GAC displayed a heterogeneous structure with rhombohedral fragments and sieve-like pores, while biochar exhibited elongated cylindrical cavities aligned along the original axis of sunflower husk particles. These features support the observed kinetic patterns: the larger pore volume in biochar facilitated faster initial uptake, whereas the high microporosity of GAC enhanced long-term retention.ATG5 Antibody Technical Information Additionally, laser scanning confocal microscopy revealed that the integral surface area of biochar exceeded that of GAC, despite its lower BET surface area, highlighting the significance of macroporous architecture in enhancing mass transfer.59-05-2 supplier
The influence of solvent composition was also critical.PMID:34772541 Acetonitrile, used to dissolve BaP, affected adsorption efficiency by altering the solvation shell around BaP molecules. At low concentrations, acetonitrile improved BaP availability for adsorption; however, higher levels suppressed sorption due to competitive solvation and increased polarity of the liquid phase. Notably, the distribution coefficient (Kd) for BaP showed a positive correlation with acetonitrile content in GAC and biochar systems, especially at a 0.5:20 solid-to-liquid ratio. In contrast, soil exhibited minimal sensitivity to solvent changes, reflecting its lower affinity and limited porosity.
These results confirm that the interaction mechanisms between BaP and sorbents are governed by both thermodynamic equilibrium and kinetic constraints. While the Freundlich model adequately described the isotherms due to surface heterogeneity, the kinetic data highlight the importance of pore hierarchy and molecular transport dynamics. Ultimately, the superior performance of carbonaceous sorbents stems from their tailored microstructure—combining high surface area, optimal pore size distribution, and favorable surface chemistry—which enables efficient capture and stabilization of persistent organic pollutants like BaP.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com
