Effects of compacting activated carbons on their volumetric CO2 adsorption performance

The practical application of activated carbons (ACs) in CO2 capture requires the materials to possess all-round high volumetric CO2 adsorption performance, but influences of compaction of ACs on the all-round volumetric adsorption performance are unclear. In this research, coconut shell-based and rice husk-based ACs were compacted to study the effects of compaction on ACs' volumetric CO2 uptake, adsorption rate, and CO2/N-2 selectivity. The compaction increased ACs' volume-based low-pressure CO2 uptake (by up to 53.8 wt%), atmospheric-pressure uptake (by up to 43.2%), CO2 adsorption rate, and CO2/N-2 selectivity, simultaneously. The main reason was that compaction changed the volumetric volume of micropores in various ranges (< 0.7 nm,< 1 nm, and < 2 nm). This change was because compaction increased tap density of ACs via reducing macropores in the range of 2 to 10 mu m and increasing carbon skeletal density. Compaction slightly affected ACs' surface functional groups, gravimetric nanopore parameters, and gravimetric CO2 uptake. The research showed that compaction enhanced ACs' all-round volumetric CO2 adsorption performance; this result was highly appealing for ACs' practical application, but was not found in previous research.