Abstract
A series of microporous granular activated carbons (GACs) has been prepared by KOH activation of walnut shell-based carbons. The characterization of GACs included the determination of microstrength and porous texture parameters (N2 adsorption at 77K and CO2 adsorption at 273K). The effect of walnut shell heat-treatment temperature (HTT) on GACs properties and CO2 uptake under pressure varying from sub-atmospheric up to 30bar has been discussed. The study reveals that walnut shell HTT has to be at least 700°C to provide a reasonable mechanical strength of GACs on activation at 800°C and KOH:carbon ratio of 2:1. Elevating HTT from 700 to 900°C suppresses porosity development (surface area SBET 2000 − 1300m2g−1, pore volume VT 0.82 − 0.56cm3g−1, micropore width L0 0.89-0.68nm) while improves mechanical strength of GACs. Walnut shell-based GACs are promising adsorbents for CO2 adsorption/separation operating under different pressure. Suitable adapting HTT allows to prepare adsorbents with sufficient mechanical strength and high CO2 uptake (at 273K up to 7.2mmolg−1 under 1bar and 18.2mmolg−1 at 30bar) with relatively low retentivity (15%) when degassed to 0.06bar.
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