Activated carbon derived from bio-waste hemp hurd and retted hemp hurd for CO2 adsorption

- Bio-waste hemp hurd and retted hemp hurd were used to produce activated carbon.
- Activated carbons retained the original hierarchical pore structures with connected macropores.
- ZnCl2 activation contributes to larger yield and specific surface area, and higher CO2 adsorption.
- Retting process corroded the larger pore channels and introduced the surface functionality.

Hemp hurd is a bio-waste by-product with unique porous structure. The morphology and thermal properties of original hemp hurd and retted hemp hurd were investigated before the carbonization. Then the biomass carbon materials from hemp hurd and retted hemp hurd were activated by using CO2 or ZnCl2. The effect of physical activation and chemical activation on the properties of derived carbon was compared. The obtained activated carbons have been evaluated for CO2 capture. The results indicated that hemp hurd has different porous structure in the cross section and longitudinal section. Retting process can further improve the thermal stability of hemp hurd. The yield, specific surface area, porosity and gas adsorption properties of activated carbons by ZnCl2 activation were superior than those of products from CO2 activation. By applying ZnCl2 activation, all the activated carbons exhibited significant of micropores with the surface area exceeding 1100 m2/g. The activated carbon derived from hemp hurd exhibited larger micropore and mesopore volumes than those derived from retted hemp hurd. Enhanced CO2 adsorption capacity of activated carbons derived from retting process may be attributed to the introduction of surface functionality.