Hierarchical porous composites derived from coal gasification fine slag for CO2 capture: Role of slag particles in the composites

Abstract

The value-added utilization coal gasification fine slag (FS) is extremely vital for minimizing the environmental problems. In this study, coal gasification FS was successfully used to prepared hierarchical porous composites (HTC) for CO2 adsorption. Furthermore, the role of slag particles (SP) in the composites was also studied through orthogonal experiments designed by acid washing conditions. Orthogonal experiments showed that the surface area of the HTCs was varied from 852 to 1295 m2/g except the samples treated by HF. The changes were primarily contributed to the SP content and the existing forms in the HTCs. There had no micropores in the HTCs treated by acid at low temperature and acid concentration because those pores were blocked by the SP. While increasing the treatment temperature and acid concentration, the acid could diffuse into the micropores to remove embedded SP and the micropores were exposed. The HTCs also proved to be attractive for CO2 capture. The highest CO2 adsorption capacity of 2.64 mmol/g at 25 °C was achieved with 1- FSHTC-AT sample. The sample not only exhibited good selectivity of CO2 over N2 of 10.8, but also had fast adsorption kinetics that it reached adsorption equilibrium in less than 2 min. Besides, there were no apparent decrease in the CO2 adsorption capacity after ten cycles. All these results suggest that fine slag has a great potential to produce HTCs for practical CO2 adsorption applications. Furthermore, it also provides a sight into the role of SP in HTC which could realize pore structure control by changing acid treatment conditions.