Solving two industrial waste issues simultaneously: Coal gasification fine slag-based hierarchical porous composite with enhanced CO2 adsorption performance

Abstract

The coal gasification fine slag (FS) is industrial waste consisting of residual carbon (RC) and slag particles (SP). High-performance hierarchical porous composite (HPC) was synthesized by chemical activation followed by hydrothermal treatment from FS. It has been realized that SP could play the positive role in developing pore structure of HPC which makes CO₂ uptake have a sharp increase. Through taking the advantage of SP, HPC has an obvious increase in surface area and pore volume from 914 to 1932 m²/g and 0.617 to 1.332 cm³/g, respectively. The changes of pore structure were mainly attributed to the two factors in a synergetic way. First, hydrothermal treatment could decrease the content of SP which acted as a ballast to reduce the surface area of activated carbon. Second, the formed silicate/aluminosilicate deposits on the carbon surface and forms silicate/aluminosilicate film on internal surface of carbon particles. This makes the meso-macropores change to micro- mesopores leading to the increase of the surface area and pore volume. The porous composites also showed high CO₂ adsorption performance. The 4-FSAC-HPC sample exhibits the highest CO₂ uptake of 3.25 mol/kg and 1.41 mol/kg at 25 and 50 °C, respectively, which is an increase of around 52% and 83% comparing with that of FSAC sample. Besides, CO₂ adsorption up to saturation can be achieved in less than 3 min. CO₂ uptake of the 4-FSAC-HPC sample was well regeneration efficiencies above 98% after 10 cycles adsorption/desorption. This work provides a new approach to prepare high-performance porous compositions using the material which contains not only carbon component but mineral matters. Furthermore, it realizes solving two industrial waste issues (fine slag and CO₂) simultaneous.

Keywords: CO(2) capture; Coal gasification fine slag; Hierarchical porous composite.