Metal incorporated biochar as a potential adsorbent for high capacity CO2 capture at ambient condition

This work investigates the development of metal incorporated biochar as a low-cost and robust adsorbent for high capacity CO2 capture at ambient condition. For this purpose, biochars were prepared through single-step pyrolysis of walnut shell (WS) at different temperatures (500, 700 and 900 degrees C). The biochar with larger specific surface area and higher microporosity fraction (WS900) was then subjected to metal impregnation followed by N-2 heat treatment. The incorporation of basic metal sites into the biochar skeleton enhanced the adsorption of acidic CO2 gas onto the metalized-biochar in the sequence of Mg > Al > Fe > Ni > Ca > rawbiochar > Na. The enhanced CO2 uptake of Mg-loaded biochar (82.0 mg/g) compared to the pristine biochar (72.6 mg/g) at 25 degrees C and 1 atm, could be explained by the synergistic effects of physical and chemical interactions, yet kinetic studies showed that physisorption was the main governing mechanism controlling the adsorption of CO2 onto the metalized-biochar. Cyclic CO2 capture studies indicated the great stability of Mg-loaded biochar upon several cycles of adsorption-desorption, with no loss in its CO2 capture capacity. It also showed easy regeneration and fast desorption kinetic which makes it a promising inexpensive candidate for real-world CO2 capture systems. Moreover, the adsorbent showed a superior capture performance towards CO2 over N-2, O-2 and CH4.