Modified sustainable lignin-based glutaraldehyde-polyvinyl alcohol-assisted porous aerogels for CO₂ adsorption

Biomass-derived aerogels are promising materials for CO₂ capture due to their eco-friendliness, tunable structure, low cost, and excellent porosity. In this study, lignin extracted from Acacia mangium was modified and incorporated into polyvinyl alcohol (PVA) matrices at varying weight percentages (0.25, 0.5, and 1 wt%) to fabricate aerogels cross-linked with glutaraldehyde (GA). The lignin was isolated using acid precipitation followed by alkaline treatment and ultrasonication to remove impurities. The resulting PVA-LN-GA-X (X = 0.25, 0.5, or 1 wt%) composite aerogels were characterized using FTIR, XRD, Raman spectroscopy, TGA, SEM/EDX, TEM, PY-GCMS, BET, and TPD-CO₂ adsorption analyses. FTIR and Raman confirmed successful integration of lignin, revealing strong hydrogen bonding and structural interactions. XRD showed semicrystalline structures, while SEM and TEM revealed a core-shell morphology with nanoscale sizes (85-96 nm). BET analysis demonstrated that PVALNGA5 had the highest surface area (665.8 m²/g) and porosity, correlating with its highest CO₂ adsorption capacity (2.4764 mmol/g). In contrast, the lowest performance was observed for unmodified PVAGA (0.1824 mmol/g). The enhanced performance is attributed to increased surface area, porosity, and active functional groups provided by lignin. Adsorption behavior followed Elovich and intraparticle diffusion kinetic models with R² values of 0.689 and 0.449, respectively. Overall, this study presents an effective strategy for producing bio-based aerogels with enhanced CO₂ capture performance, offering potential for scalable and sustainable applications in environmental remediation.