# Analysis of Technologies for Carbon Dioxide Capture from the Air
## 2 DAC Technologies
### Adsorption
#### 2.2.2 Chemisorbents
 & **Co./N** & **Method** & **Reference** \\ \hline Mergeness carbon & Polycrystalline (7 PI) 55\%-v/v/v & 298 K, 80\%- relative humidity & 400 & 2.58 & [7] \\ \hline Mergeness carbon & Polycrystalline (7 PI) 55\%-v/v & 298 K & 5000 & 3.34 & & [7] \\ \hline Mergeness carbon & Biased Polycrystalline (7 PI) 55\%-v/v & 330 K, 50\%- humidity & 400 & 1.71 & IB & [7] \\ \hline Allowers’s alumina method & Biased Polycrystalline (7 PI) 40\%-v/v & 303 K & 400 & 0.75 & Gevimetries & [7] \\ \hline Non-polar resin (9 PI) & Polycrystalline (7 PI) 55\%-v/v & 343 K & 400 & 2.26 & [7] \\ \hline Mergeness polymer & Polycrystalline (7 PI) 20\%-v/v & 308 K & 400 & 0.2 & & [7] \\ \hline SSA-15 & Polycrystalline (7 PI) 9 PI prepared by IGCO & 303 K & 400 & 0.31 & & [7] \\ \hline SSA-15 & Poly(polycrystalline) (7 PI) prepared by IGCO & 303 K & 400 & 0.25 & & [7] \\ \hline SSA-15 & Poly(polycrystalline) (7 PI) prepared by IGCO,H & 303 K & 400 & 0.15 & & [7] \\ \hline SSA-15 & Poly(polycrystalline) (7 PI) prepared by IGCO,H & 303 K & 400 & 0.17 & & [7] \\ \hline SSA-15 & Trans(In)Determining (TTE) & 256 K & 400 & 3.6 & 0.2 & & [7] \\ \hline Nanodiffinal cellulose (9 NC) & PIFI(Polycrystalline (7 PI) 44\%-v/v & 20\%- relative humidity & 400 & 0.5 & IB & [7] \\ \hline Nanodiffinal cellulose (9 NC) & PIFI(Polycrystalline (7 PI) 45\%-v/v & 80\%- relative humidity & 400 &  
An amine-functionalized sorbent made by PEI impregnation onto alumina has been studied in the work of [PERSON] et al. [78]. An adsorption capacity of 0.75 molCO\({}_{2}\)/kg at a high amine loading, with 303 K and simulated ambient air, was evaluated for a larger extruded monolith sorbent, and it was found to be higher than that of an alumina powder sorbent (0.7 molCO\({}_{2}\)/kg). In addition, the authors found that, for the first sorbent, adsorption capacities for two to five cycles were stable but slightly lower than that for one cycle due to minor PEI leaching or rearrangement in the monolith, which has been observed for powder sorbents. The same amine, PEI, was impregnated with a loading up to 21 %wt onto a microporous polymer (PIM-1); an uptake of 0.2 molCO\({}_{2}\)/kg at 308 K for simulated air and 1 molCO\({}_{2}\)/kg for a flue gas with 14% of CO\({}_{2}\) were measured [80]. However, at a higher amine loading, the CO\({}_{2}\) adsorption capacity was reduced due to the inaccessibility of the amine sites. [PERSON] et al. [74] evaluated how different kinds of PEI impregnated onto funnel silica (linear, branched, with low and high molecular weights, respectively, of 1800 and 25,000 Da) influenced adsorption capacity and found the best uptake for the branched sample with a low molecular weight at a loading of 33 %wt (56 mgCO\({}_{2}\)/g). At a higher amine loading (50 %wt), higher adsorption capacities were obtained of up to 107.3 mgCO\({}_{2}\)/g for the PEI with an 800 Da molecular weight. However, PEI of lower molecular weight can be more prone to leaching than homologues with higher molecular weights. This could lead to a loss of capacity over time and the possible contamination of downstream equipment. [PERSON] et al. [79] reported the impregnation of PEI onto non-polar resin HP20, measuring the adsorption capacity for pure CO\({}_{2}\) and simulated air with a CO\({}_{2}\) concentration of 400 ppm. The values for the investigated parameter were, respectively, 4.122 molCO\({}_{2}\)/kg and 2.26 molCO\({}_{2}\)/kg. This material exhibits promising potential for CO\({}_{2}\) capture from ambient air. Moreover, the authors found that a pore size of 43-68 nm is responsible for diffusion/adsorption phenomena, using a non-local density functional theory. On the other hand, they verified that temperature has a negative effect on adsorption due to exothermic reactions. Amine mixtures have been investigated. In this context, [PERSON] and [PERSON] [64] analyzed the adsorption capacity of a sorbent obtained by the impregnation of silica and polymer supports with tetraethylenepentamine (TEPA) and PEI at different temperatures and CO\({}_{2}\) concentrations.