Coal gasification fine slag and nitrogen-containing waste co-hydrothermal preparation of porous materials for CO₂ adsorption

A new adsorbent was successfully prepared by hydrothermal treatment and chemical activation through coal gasification fine slag (CGFS) and blue algae (BA) as raw materials and used for CO2 capture. The CO2 chemisorption capacity of the adsorbent was further enhanced by taking advantage of the nitrogenous bases contained in the BA. In the hydrothermal process, the addition of BA significantly increased the content of pyrrole nitrogen in the adsorbent. In the activation process, pyrrole nitrogen gradually changed into pyridine nitrogen and graphite nitrogen. Increased BA addition result in a higher specific surface area and microporosity of the adsorbent. The CO2 adsorption performance test proved that the CGFS-50%-CA sample has the strongest CO2 adsorption capacity at low temperature, up to 15.59 cm³/g, which is mainly through physical adsorption, and the CGFS-10%-CA sample has the strongest CO2 adsorption capacity at high temperature, up to 7.31 cm³/g, which is mainly through chemical adsorption. CO2 uptake of the CGFS-10%-CA sample was well maintained after 10 cycles, with regeneration efficiencies above 99%. The results indicate that the novel adsorbents with coexistence of physical and chemical adsorption have great potential for CO2 adsorption applications.