Amine-modified silica zeolite from coal gangue for CO₂ capture

During coal mining process, a large amount of coal gangue is produced. Due to its low utilization, accumulation of coal gangue has caused serious environmental pollutions. In this work, silica zeolite MCM-41 and amine-modified MCM-41 were prepared from coal gangue for CO₂ capture. MCM-41 were prepared at different pH (8, 9, 10) and different calcination temperatures (450 °C, 500 °C, 550 °C) and the effects of pH and temperature were investigated. Polyethyleneimine (PEI), was loaded onto MCM-41 at different loadings (30%, 40%, 50%, 60%) to improve its CO₂ capture performance. The CO₂ capture capacity and cyclic stability of amine modified MCM-41 were also evaluated. The results showed that preparation pH and calcination temperature both have effect on MCM-41. The specific surface area reaches a maximum of 642.17 m² g⁻¹ at 550 °C and pH of 9. Amine modification improves the CO₂ capture ability of MCM-41. As the PEI loading amount increased from 0 to 60%, the CO₂ capture capacity showed a significant improvement from 0.125 to 1.742 mmol g⁻¹. After 5 cycles, its CO₂ uptake capacity still remained 70%.