Effect of pore morphology on adsorption of methylene blue and phenol in micro-mesoporous carbons

Micro–mesoporous carbonaceous adsorbents were synthesized via polycondensation of resorcinol and furfural using soft-templating approach. Four templated samples were prepared with non-ionic surfactants Pluronic F-127 and P-123; a non-templated material was also synthesized for comparison. TEM showed that three templated carbons exhibited wormlike mesopores, while one had an ordered mesoporous structure. Nitrogen sorption and thermoporometry analyses revealed mesopore volumes from 0.19 to 0.40 cm³ g⁻¹ and micropore volumes from 0.19 to 0.27 cm³ g⁻¹. Higher template amount (5 g) resulted in broader mesopore distributions (up ∼15–20 nm) than lower amount (2 g, up ∼10 nm). All templated samples exhibited enhanced microporosity relative to non-templated reference, attributed to improved mesopore accessibility. Adsorption kinetics of phenol and methylene blue from aqueous solutions were evaluated using four kinetic models. The pseudo-second-order model provided the best fit based on Akaike information criterion. Mesopore arrangement (ordered vs. wormlike) significantly influenced adsorption behaviour. For phenol, adsorption capacities were similar across all templated samples, reflecting its preferential uptake in micropores, yet the ordered mesoporous carbon exhibited a notably lower rate constant, suggesting hindered diffusion due to less interconnected mesopores. For methylene blue, which preferentially adsorbs in mesopores and larger micropores, reduced adsorbed amount was observed in the ordered sample. This suppression correlated with limited water intrusion into mesopores, as confirmed by TPM, emphasizing the importance of surface wettability. These results demonstrate that both mesopore morphology and hydrophilicity, in addition to pore size, play a crucial role in governing adsorption performance of carbon materials in aqueous media.