Construction of ultra-microporous activated carbons derived from waste distiller's grains for efficient CO2 adsorption

[Display omitted] •Construction of ultra-microporous activated carbons derived from waste distiller's grains is demonstrated.•Texture properties and CO2 adsorption performance of the distiller's grains based activated carbon are studied.•Distiller's grains based activated carbon is found to be a very efficient CO2 adsorbent (6.34 mmol·g−1 at 273.15 K and 1 bar).•Excellent thermal stability enables the biochar to be recycled multiple times.•Thermodynamics and kinetics of CO2 adsorption are studied. Distiller's grains, as the wine-making solid waste, are considered a biomass resource with low cost, which can be used for the preparation of activated carbon, showing excellent application prospects. Here, a series of ultra-microporous activated carbons were prepared by carbonization and activation with the different activators using waste distiller's grains as the precursors. The effects of activators species, activation temperature, and activator dosage on the properties and structure of the activated carbons were investigated, respectively. As-prepared activated carbons was found to be a very efficient CO2 adsorbent with up to 6.34 mmol·g−1 at 273.15 K and 1 bar. The adsorption of CO2 was determined by the ultra-micropore structure, pore size distribution, and pore volume, as well as the heteroelements (N and O) contained in the activated carbon. Furthermore, the activated carbon can be recycled many times without decline in adsorption performance of CO2. This study not only develops a new pathway for resource utilization of distiller's grains, but also provides an alternative method for the application of low-cost biochar in the field of CO2 adsorption.