Development of a novel type hierarchical porous composite from coal gasification fine slag for CO2 capture

A novel type hierarchical porous composite is successfully synthesized through chemical activation followed by the hydrothermal treatment using coal gasification fine slag (FS) as the raw material. This study realized pore structure development for the porous composite through taking the advantage of slag particles to achieve further better CO2 adsorption capacity. The hierarchical porous carbon (FSHPC) prepared from FS by chemical activation has obvious macropore structure. After being treated by hydrothermal synthesis method, FSHPC formed a well-developed pore structure and the surface area increased by 735 m(2)/g. Among (1-16)-FSHPC-NM samples, 4FSHPC-NM sample has the largest surface area of 1713 m(2)/g, higher than that of porous carbon whose mineral matter is almost entirely removed (1524 m(2)/g). The mechanisms for the enhancement of pore structure by hydrothermal treatment are: (1) the decrease of the content of slag particles (SP) which acted as a ballast and blocked the pore of FSHPC; (2) the silicate/aluminosilicate film covering the meso-/macro-pores surface and the pores transformed into micro-/meso-pore. The FSHPC-NM samples showed remarkable CO2 adsorption performance. The 4-FSHPC-NM sample exhibits the highest CO2 uptake of 2.97 mol/kg and 1.23 mol/kg at 25 degrees C and 50 degrees C, respectively. Compared with the CO2 adsorption capacity of FSHPC, the CO2 adsorption capacity increased by 1.03 mol/kg after hydrothermal treatment, due to the developed pore structure and more active sites (metallic cations) for CO2 adsorption. 4-FSHPC-NM sample has the best CO2 adsorption rate, whose CO2 adsorption equilibrium is achieved within 5 min. CO2 uptake of the 4-FSHPC-NM sample was well maintained after 15 cycles. All these results suggest that hierarchical porous composite has an enormous potential to be reused for practical and industrial CO2 adsorption applications.