## 3 Results and Discussion
### Breakthrough Experiments under Dry Conditions
These values, which were calculated according to Equation (A5), were considerably higher than those reported by [PERSON] et al., (20-30) [13] and [PERSON] et al., (17.4-29.3) [14] from multicomponent adsorption measurements. Interestingly, the apparent CO\({}_{2}\)-over-N\({}_{2}\) selectivities at 25 \({}^{\circ}\)C (see Table 4) were quite similar to those measured under dynamic conditions, with the exception of the AC_VS_600 sample. The fact that the selectivity significantly increased for this material under dynamic conditions could be explained by differences in pore size distribution. As can be deduced from the pore size distributions shown in Figure 4,  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline  & & \multicolumn{4}{c}{**Activated Biochar**} \\ \cline{3-5}  & _AC\_VS\_600_ & _AC\_VS\_600\(P\) & _AC\_WS\_500_ & _AC\_WS\_500\(P\) \\ \hline Mass of adsorbent (g) & 15.1 & 16.8 & 26.9 & 27.8 \\ Absolute pressure in adsorption steps (kPa) & 111.8 \(\pm\) 0.5 & 111.9 \(\pm\) 0.7 & 111.4 \(\pm\) 0.1 & 111.5 \(\pm\) 0.2 \\ Absolute pressure in desorption steps (kPa) & 21.5 \(\pm\) 0.1 & 31.3 \(\pm\) 0.1 & 31.3 \(\pm\) 0.1 & 31.1 \(\pm\) 0.1 \\ cycle 1 & 0.992 & 0.936 & 0.895 & 0.959 \\ cycle 2 & 0.891 & 0.799 & 0.763 & 0.869 \\ \(q_{\rm CO2}\) (mmol g\({}^{-1}\)) & cycle 3 & 0.860 & 0.731 & 0.706 & 0.764 \\ cycle 4 & 0.852 & 0.696 & 0.676 & 0.727 \\ cycle 5 & 0.834 & 0.682 & 0.616 & 0.667 \\ cycle 1 & 76.3 & 80.7 & 77.9 & 80.9 \\ Percentage of total & cycle 2 & 76.7 & 77.5 & 71.0 & 78.8 \\ CO\({}_{2}\) uptake at & cycle 3 & 77.3 & 75.4 & 68.2 & 77.7 \\ breakthrough time & cycle 4 & 76.6 & 76.3 & 65.8 & 74.8 \\ cycle 5 & 76.2 & 73.7 & 64.7 & 74.7 \\ cycle 1 & – & – & – & – \\ cycle 2 & 89.8 & 85.4 & 85.2 & 90.6 \\ regeneration efficiency (\%) & cycle 3 & 86.7 & 78.1 & 78.9 & 79.7 \\ cycle 4 & 85.9 & 74.4 & 75.5 & 75.8 \\ cycle 5 & 84.1 & 72.9 & 68.8 & 69.6 \\ cycle 1 & 56.7 & 58.6 & 49.4 & 48.6 \\ cycle 2 & 49.2 & 51.9 & 51.9 & 46.6 \\ Selectivity CO\({}_{2}\)/N\({}_{2}\) & cycle 3 & 44.9 & 49.4 the AC_VS_600 sample clearly exhibited a broader distribution, with a significant contribution in the ranges of relatively large micropores (0.8-2.0 nm) and relatively narrow mesopores (up to 15 nm). The higher availability of these pores can facilitate the adsorption of a relatively high amount of N\({}_{2}\) under static conditions. However, under dynamic conditions, the much shorter residence time of the gas phase (around 13 s) could lead to a decreased N\({}_{2}\) uptake, due to diffusional limitations. On the basis of the results obtained at 25 \({}^{\circ}\)C, we decided to assess the performance at 50 \({}^{\circ}\)C of the AC_VS_600 and AC_WS_500_P materials. Table 6 summarizes the results obtained for this adsorption temperature, whereas Figure 5 shows the respective CO\({}_{2}\) breakthrough curves. The AC_VS_600 adsorbent exhibited a very good performance, especially in terms of CO\({}_{2}\) uptake (with values very close to that deduced from the adsorption isotherm) and stability over the adsorption/desorption cycles  
Figure 4: Pore size distribution of the adsorbents: (**a**) narrow micropores (deduced from the CO\({}_{2}\) adsorption isotherms at 0 \({}^{\circ}\)C), and (**b**) pores widths ranging from 1.0 to 15 nm (deduced from the N\({}_{2}\) adsorption isotherms at \(-\)196 \({}^{\circ}\)C). (see Figure 5a). The relatively low CO\({}_{2}\) adsorption capacity measured for the first cycle (0.54 mmol g\({}^{-1}\)) and related regeneration efficiencies (higher than 100%) could be explained by slight differences in experimental conditions, especially the CO\({}_{2}\) partial pressure in the feeding gas stream, which was slightly lower than the average value used for the rest of cycles (15.2 kPa vs. 15.9 kPa). Regarding the performance of the AC_WS_500_P sample, a considerably decrease in the CO\({}_{2}\) uptake (18.2%) was observed after five cycles.