A novel amine functionalized porous geopolymer spheres from municipal solid waste incineration fly ash for CO₂...

Municipal solid waste (MSW) incineration fly ash (FA) is classified as hazardous waste, and strategies for recycling FA have attracted attention. In this study, the porous geopolymer spheres (PGS) were prepared from FA by the foaming-suspension-solidification method, and then the PGS were functionalized with tetraethylenepentamine (TEPA) to capture CO₂. The results showed that washing pretreatment and the addition of H₂O₂ foaming agent enhanced the pore volume and specific surface area of PGS. The CO₂ adsorption capacity of amine-functionalized PGS exhibited a trend of increasing and then decreasing in the range of 35-80 °C. The maximum adsorption capacity of TEPA-WPGS3 was 2.55 mmol/g at 65 °C higher than expected for the average of TEPA and PGS. This was because PGS improved the dispersion of TEPA, thus exposing more active sites of TEPA and making it more likely to interact with CO₂. The adsorption efficiency of amine-functionalized PGS decreased by only 2.4% after 10 cycles, indicating that it has excellent regeneration performance. In addition, amine-functionalized PGS, which showed excellent CO₂ adsorption capacity, had a significant ability to selectively adsorb CO₂ and the adsorption capacity of the rapid stage accounted for approximately 80% of the saturated adsorption capacity. This study shows that FA-derived geopolymers have excellent CO₂ adsorption properties and provides a new method for the resource utilization of FA.