壳聚糖水热炭低浓度KOH活化制备多孔炭材料及其CO 2 吸附性能

Hydrothermal treatment of biomass is effective to produce hydrochar, but it usually has low surface area that not suitable for the direct use as adsorbent for CO2 capture. Herein, chitosan was employed as a precursor for carbon prepared by a combined hydrothermal treatment and mild KOH activation method. The effect of additive salt (eutectic salt of KCl/LiCl with a mass ratio of 5.5/4.5) in hydrothermal treatment and activation temperature on the porosities and surface chemical states of the obtained carbons and their CO2 capture performances were studied by N2 adsorption, XPS, SEM and XRD. Results indicated that the increased activation temperature enhance the porosities of the carbons. Additive salt introduced mesopores in hydrochar, slightly reduced the surface areas of porous carbons after activation treatment, but was useful to reduce N-species loss in hydrothermal treatment and activation. The carbons from salt-assisted hydrochar exhibited much larger CO2 uptakes as compared with that of counterparts without salt under ambient conditions, suggesting the porosity was not a single factor that determines the CO2 uptake. The CO2 uptake on the carbon from salt-assisted hydrochar activated by KOH at 600 °C was the highest (highly up to 4.41 mmol/g) although its surface area was only 1249 m2/g, which indicated that CO2 uptake was jointly determined by the microporosity and active N-species in the carbon material.