Sawdust wastes-derived porous carbons for CO2 adsorption. Part 2. Insight into the CO2 adsorption enhancement mechanism of low-doping of microalgae

Abstract

Porous carbons produced using poplar sawdust are promising CO2 adsorbent applied under ambient conditions due to the low-cost preparation approach. CO2 uptake capability of the porous carbons produced from poplar sawdust can be effectively enhanced via doping an approximate amount of microalgae. The N-doped porous carbon produced from poplar sawdust using microalgae as N-doping source (microalgae/poplar sawdust=0.5:1) possesses an excellent capacity of 4.14 mmol·g−1 for CO2 uptake, nearly over 1.7 times that of the carbon without N-doping. The improved performance for CO2 uptake of porous carbons is mainly ascribed to the two-fold effect of microalgae doping: (i) generating extensive narrow pores and channels within the porous carbons owe to co-pyrolysis; (ii) introduction of N-containing moieties derived from the intrinsic N of microalgae increasing the surface polarity and alkalinity. The N-doped porous carbon granules derived from poplar sawdust are inferior to the powdered porous carbons for CO2 adsorption due to the destroyed structure. They still maintain the relatively desirable capability for CO2 adsorption (~3.0 mmol·g−1 during 5 cycles) and good mechanical property (10.96 ± 1.43 Mpa). Comprehensively considering the advantaged properties (low-pressure drop, high bulk density) required for practical application, the N-doped porous carbon granules derived from poplar sawdust with low-doping of renewable microalgae possess strong practicability.