Synergistic bio-physicochemical enhancement of microalgal CO₂ fixation via Fe₂O₃ nanoparticle-embedded nanofiber...

Algae-based carbon capture and utilization (CCU) technique offers a sustainable strategy for CO₂ mitigation, but its efficiency is often limited by poor gas-liquid mass transfer and unstable carbon availability. Here, this study developed an iron oxide nanoparticle (Fe₂O₃NPs)-incorporated electrospun nanofiber membrane to enhance CO₂ capture and microalgal fixation. Results revealed that the Fe₂O₃NPs was able to reduce fiber diameter, refine pore architecture, and increase specific surface area, thereby the improved CO₂ adsorption. In Chlorella cultivation, the final biomass concentration and CO₂ biofixation rate of modified membrane increased by respective 11.6%±1.2% and 14.3% compared with that of pristine nanofibers. Furthermore, the modified membrane significantly promoted the early-stage biofilm formation, yielding biofilms that were 47.9% thicker, denser, and exhibited increased rougher surface. Nanoparticle-induced "microhooks", together with enhanced EPS secretion, strengthened algal attachment, increased cell density, and improved spatial homogeneity, thus creating a favorable microenvironment for rapid biofilm development. Cellular analyses demonstrated that membranes modified with Fe₂O₃NPs increased intracellular ATP by 45.6%, superoxide dismutase activity by 39.9%, and specific growth rate by 41.8% compared to the blank controls, indicating enhanced metabolic activity and stress resistance. Physicochemical characterization further showed that a reduction in electrostatic repulsion and an increase in hydrophobicity. Meanwhile, Lifshitz-van der Waals (U^LW) and Lewis acid-base (U^AB) interaction energies increased by approximately twofold and 2.74-fold, respectively. These changes synergistically enhanced initial algal adhesion and attachment stability, facilitating CO₂ enrichment. In summary, this work elucidates the synergistic bio-physicochemical mechanisms underlying nanoparticle-modified membranes and specify their potential for advancing efficient microalgae-based CCUS technologies.