Carbon negative technology empowered adsorption behaviour and mechanism of porous geopolymer

Porous materials have a wide range of applications in the adsorption of pollutants. In this study, porous geopolymer (PG) was prepared by using steel slag and fly ash as raw materials. The changes in the mechanical properties, microstructure, and methylene blue (MB) removal rate of PG caused by carbonation were observed. The results showed that the filling of CaCO₃ and the increase of polymerization degree led to the increase of PG compressive strength during carbonation, and the compressive strength of carbonated PG reached 2.27 MPa. According to BET and XPS results, carbonation resulted in an increase in the specific surface area and surface hydroxyl functional groups of PG. Compared to non-carbonated PG, there was a 34% increase in the removal rate and adsorption capacity of MB. The maximum adsorption capacity of MB by carbonated PG was 27.61 mg/g. Additionally, FTIR analyses suggested that the electrostatic interactions and hydrogen bonding were the primary dye adsorption mechanisms, and the MB adsorption by carbonated PG conformed to fit the Freundlich isotherm and pseudo-second-order kinetic models.