The feasibility of cost-effective manufacturing activated carbon derived from walnut shells for large-scale CO2 capture.

Abstract

The economic potential of activated carbon (AC) synthesis from walnut shell biomass for CO2 capture was evaluated in the present study. For this purpose, the chemical activation was employed to manufacture ACs and the effect of different impregnation ratios of activation agents, comprising KOH (KH) and H3PO4 (HP), onto the properties of fabricated ACs was examined. The obtained results demonstrated that the synthesized AC by HP activation with an impregnation ratio of 1:2.5, which was identified as HP2.5, possesses the highest surface area (1512.6m2/g), micropore volume percentage (74.65%), and CO2 adsorption (3.55mmol/g) at 1bar and 30°C. Moreover, the equilibrium CO2 adsorption data for HP2.5 were better fitted with the Freundlich model, indicating the multilayer CO2 adsorption onto the heterogeneous AC surface dominantly through a physisorption process. In addition, the economic estimations revealed a cost of about $1.83/kg for the ultimate production that was significantly lower than the most of available CACs in the market. Therefore, walnut shells can be considered as a cost-effective and promising biomass source from a scale-up point of view.