CO2 Adsorption study on pure and chemically activated chars derived from commercial biomass gasifiers
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The carbonaceous by-product of biomass gasification processes is known as char. Although nowadays char is treated as a waste, it could be valorized as cheap precursor for activated carbons (ACs) due to their similarities in terms of physical-chemical properties and mechanism of formation. In particular, this study wants to assess char suitability as substitute/precursor of AC for CO2 adsorption. Five chars were taken from five different commercial biomass gasifiers installed in South-Tyrol (Italy) and characterized through elemental analysis, physisorption analysis, and scanning electron microscopy. CO2 adsorption/desorption capacity of chars were investigated through thermogravimetric analysis and their performances were compared with two commercial ACs selected as reference.The effects of adsorption temperature (Tads=50– 75–100 °C), CO2 concentration (CO2:N2=1:1– 1:4), chemical activation (with KOH or ZnCl2), and adsorption cycles were investigated. The highest uptake (3.7%) was measured for char activated with KOH, at Tads =50 °C and CO2:N2=1:1.