Publication

Abstract : Adsorption using biodegradable polymeric nanofibers has attracted increasing attention as a sustainable approach for wastewater treatment; however, the factors governing adsorption selectivity in low-surface-area polymer systems remain insufficiently understood. In this study, electrospun sodium alginate-poly(vinyl alcohol) (SA-PVA) nanofibers were developed as biodegradable adsorbents to investigate the selective adsorption of methylene blue (MB) and brilliant green (BG), two cationic dyes with similar charge characteristics but different molecular sizes and steric configurations. Despite a relatively low BET surface area of 4.16 m² g⁻¹ , the Ca²⁺-crosslinked nanofibers exhibited Langmuir adsorption capacities of 54.85 mg g⁻¹ for MB and 8.89 mg g⁻¹ for BG. Kinetic analysis indicated a significant contribution of diffusion-controlled transport to the adsorption process, while intraparticle diffusion analysis highlighted the importance of molecular accessibility within the nanofibrous network. Equilibrium adsorption data were well described by the Langmuir isotherm model, indicating adsorption at chemically accessible functional sites. Thermodynamic analysis confirmed that the process was spontaneous and exothermic. The higher adsorption of MB compared with BG is attributed to its smaller molecular size, which facilitates diffusion through the nanofibrous matrix, together with stronger electrostatic and hydrogen-bonding interactions with the hydroxyl- and carboxylate-rich SA-PVA network. DFT and QTAIM analyses further supported this interpretation by revealing stronger interfacial interactions for MB than BG. Collectively, these findings demonstrate that adsorption in electrospun polymeric nanofibres is governed by the combined effects of diffusion-mediated transport and specific dye-polymer interactions rather than surface area alone. The combined experimental and theoretical approach provides mechanistic insight into selective adsorption in biodegradable nanofibrous systems and offers guidance for the rational design of sustainable adsorbents for aqueous contaminant removal.