Tailoring Functional Properties in Hybrid Composites through Geopolymerization: From Fire Resistance to Pollutant Capture

Geopolymers[1], characterized by their three-dimensional Si-O-Al frameworks, are gaining increasing attention for their low environmental impact and notable functional properties, in respect of traditional Portland Cement. This work explores their applications beyond structural uses, focusing on the development of nanocomposite materials[2] with enhanced flame-retardant and adsorption performance. Two systems were designed and studied: Hydroxypropyl cellulose/halloysite nanotube (HPC/HNTs) composites for flame-retardant applications and alginate/HNTs gel beads for pollutant absorption were geopolymerized to enhance the functional potential of clay-based systems, resulting in significantly improved fire resistance and sorption capabilities. In both cases, successful geopolymer formation was confirmed through X-ray diffraction (XRD), Thermogravimetric (TGA), and Scanning electron microscopy (SEM) analyses. Thermogravimetric measurements were also employed to evaluate the CO2 adsorption capacity of the samples, while dynamic mechanical analysis (DMA) provided insight into their mechanical properties. Geopolymerized gel beads exhibited markedly improved CO2 uptake compared to their non-geopolymerized counterparts, attributed to increased porosity visible in SEM micrographs. Hydrocarbon absorption tests with dodecane further confirmed the enhanced sorption capacity of the geopolymerized beads. In parallel, HPC/HNTs composites treated with the same geopolymerization strategy displayed significantly improved flame-retardant behavior, with flames extinguishing in less than 0.5 seconds after ignition removal, far outperforming untreated films. These findings demonstrate the versatility of geopolymers in functional composite systems, offering a pathway toward materials that combine environmental sustainability with high performance in thermal and adsorption applications.