Ultra-microporous adsorbents prepared from vine shoots-derived biochar with high CO2 uptake and CO2/N-2 selectivity

There is a growing interest in developing renewable biomass-based adsorbents to be used in numerous applications, including CO2 capture in postcombustion conditions. In the present study, several activated carbons (ACs) were produced from vine shoots-derived biochar through both physical and chemical activation using CO2 and KOH, respectively. The performance of these ACs was tested in terms of CO2 uptake capacity at an absolute pressure of 15 kPa and at different temperatures (0, 25, and 75 degrees C), apparent selectivity towards CO2 over N-2, and isosteric heat of adsorption. At 25 degrees C, the chemically ACs with KOH impregnation exhibited the highest CO2 adsorption capacity, which was similar or even higher than those recently reported for a number of carbon-based adsorbents. However, the AC prepared through physical activation with CO2 at 800 degrees C and a soaking time of 1 h appears as the most promising adsorbent analyzed here, due to its higher CO2 uptake capacity and adsorption rate at relatively high temperature (75 degrees C), its relatively high selectivity at this temperature, and its apparently low energy demand for regeneration. Given that physical activation with CO2 is more feasible at industrial scale than chemical activation using corrosive alkalis, the results reported here are encouraging for further development of vine shoots-derived adsorbents.