Effects of cellulose addition on the physicochemical properties, pore structure and iodine adsorption of lignin-based biochar

[Display omitted] •Cellulose promoted the formation of biochar and its pore structure.•Carbon nanotubes were successfully prepared with the addition of 40 wt% cellulose.•Iodine adsorption occurred at two different active sites and could be described by pseudo-second order kinetics.•The iodine saturation adsorption capacity was the highest with the addition of 40 wt% cellulose.•Strong iodine adsorption performance was mainly caused by the developed surface functional groups. The effects of different doped cellulose contents (0 ∼ 50 wt%) on the physicochemical properties, surface morphology, pore structure and iodine adsorption behavior of a lignin-based biochar were studied, and carbon nanotubes (CNTs) were successfully prepared during the pyrolysis process. The results showed that after the addition of cellulose, more micropores were formed on the surface of biochar, but cellulose inhibited the pyrolysis of the lignin to a certain extent. In particular, biochar with 40 wt% cellulose added exhibited a higher yield and more surface functional groups; additionally, CNTs were successfully prepared with this biochar sample. The iodine adsorption kinetics showed that the pseudo-second order kinetic model provided the best fit to the iodine adsorption data for this biochar. L6-C4 exhibited a higher saturation adsorption capacity of 467.38 mg·g−1 in the equilibrium adsorption experiment. Finally, combined with the Fourier transform infrared (FTIR) results, it was found that the enhanced iodine adsorption performance of L6-C4 was mainly caused by its surface functional groups.