Development of microporous-activated carbons derived from two renewable precursors for CO2 capture

Abstract

Wood sawdust from an invasive arboreal species, Parkinsonia aculeata, and seeds from a tropical fruit of massive consumption, Pouteria sapota, were used as precursors for the development of activated carbons (ACs) directed to CO2 adsorption. Chemical activation employing KOH as activating agent and pre-established experimental conditions was applied. Main physicochemical properties of the ACs in relation to their CO2 adsorption performance were examined. The ACs developed from the wood sawdust and the seeds presented specific surfaces areas of 770 and 1000 m2 g−1, respectively, with their porosity development resulting essentially microporous (< 2 nm). They also showed a similar content of acidic surface groups, but basic functionalities of the former duplicated those of the latter. Maximum CO2 adsorbed at equilibrium (273 K and 100 kPa) was 5.0 mmol g−1 and 4.4 mmol g−1 for the samples derived from the sawdust and the seeds, respectively. On the other hand, CO2 adsorption capacities mimicking post-combustion conditions, as evaluated from thermogravimetric assays and breakthrough curves obtained in a packed-bed column, were approximately 1 mmol g−1, indicating a good CO2 adsorption performance for both ACs. Nevertheless, those derived from the wood sawdust with a notorious preeminence of micropores (~ 93%), narrower pore size distribution centered around 1 nm, and a higher content of basic functionalities than the ACs obtained from the seeds showed a relatively better performance. The CO2 removal capacity of the activated carbons was not noticeably affected after five CO2 adsorption?desorption cycles, with both samples almost keeping their initial CO2 adsorption capacity.