Moisture-Driven Carbon Capture: An Examination of Activated Carbon Loaded with Anions

Abstract

The imminence of climate change driven by greenhouse gas emissions has necessitated the exploration of novel negative emissions technologies to reduce CO2 levels in the atmosphere. However, current energy costs for these technologies remain high. Moisture-driven direct air capture allows sorbents to adsorb CO2 depending on humidity levels, and requires significantly less amounts of energy for sorbent regeneration. The group synthesized 6 samples of 0.2 g activated carbon powder loaded with 0.2 mL of varying solution (Na2CO3 and K3PO4) and varying concentrations (1 M, 2 M, and 4 M), along with an untreated sample of activated carbon. Each sample was subjected to a full moisture swing cycle where the maximum and minimum CO2 levels of the air in the moisture-driven direct air capture system were recorded. The group found that nearly all loaded activated carbon samples exhibited a larger CO2 swing range than the pure activated carbon. The 1 M Na2CO3 and 2 M K3PO4 samples exhibited the highest CO2 swing ranges of 571.60 ppm and 829.16 ppm, respectively. The 4 M Na2CO3 and 1 M K3PO4 samples exhibited the lowest CO2 swing ranges of 546.65 ppm and 410.84 ppm, respectively. The results show that activated carbon does not necessarily gain better CO2 capture performance with increased anion loading. In addition, loading activated carbon with lower concentrations of ionic solution corresponds to faster CO2 desorption rates, while higher concentrations corresponds to faster CO2 adsorption rates.