Activated Carbon–Geopolymer Composites: Influence of Particle Size and Content on CO2 Adsorption and Mechanical and Thermal Properties

This study aims to develop and characterize innovative geopolymer composites by incorporating activated carbon into a geopolymer matrix to create a novel, effective sorption material suitable for non-dusty or medium-temperature environmental applications. Specifically, it examines the impact of using a single source of activated carbon, both in its original granular form and milled form, at two different loading levels for each. The research focuses on evaluating how these variations influence the textural, adsorption, mechanical, and thermal properties of the resulting geopolymer composites, with particular attention to strength and thermal stability under operational conditions. The CO2 adsorption capacity of the composites measured at 25 °C and pressure up to 0.1 MPa varied from 48.8 to 60.0 mg.g−1, with the highest performance observed at a lower content of the granular form, while commercial pure activated carbon reached 120.8 mg.g−1. However, incorporation of a granular form negatively affected thermal stability (approximately 20 wt.% weight loss) and significantly reduced compressive strength (below 45 MPa) due to increased material inhomogeneity. Despite these limitations, both types of composites show promising potential for environmental applications. However, further optimization is required to balance sorption capacity, strength, and thermal stability.