Assessment of Magnetite/Carbon Composites Capacity in CO₂ Adsorption under Sound Assisted Fluidization Conditions

Abstract

Among post-combustion CO2 capture strategies, adsorption with solid sorbents is considered to be one of the most promising options. However, the performances of solid sorbents under typical flue gas concentrations (5- 15 %vol. and atmospheric pressure) have been poorly investigated. Under these operating conditions the CO2 uptake capacity is primarily influenced by material functionality effects rather than material pore metrics, therefore, materials with a distinctive surface chemistry (presence of activated surface atoms or sites) are expected to find applications in adsorption technologies. Hence, the sorbent selection became a key point because the materials should be both convenient from the economic point of view and versatile under post-combustion conditions. Recent studies of CO2 adsorption on low-cost iron metal oxide surfaces strongly encourage the possible use of metal oxide as sorbents, but the tendency of magnetite particles to agglomerate causes a lowering of CO2 uptake capacity. The dispersion of magnetite nanoparticles on carbonaceous matrix appears to be a promising strategy to overcome this drawback. This work investigates the CO2 adsorption behavior of composite materials prepared coating a low-cost commercial carbon black (CB) with magnetite fine particles. The CO2 capture capacity of composites produced with different CB load was evaluated in terms of the breakthrough times measured at atmospheric pressure and room temperature in a lab-scale fixed bed reactor. It was established that when the amount of CB in the composite is in the range 14.3-60 % the CO2 uptake is remarkably increased with respect to the pure magnetite. The best performing CB–FM composite (50 % of CB load) was selected to verify the possibility of carrying out a cyclic adsorption/desorption operation in a sound assisted fluidized bed. The results showed that the selected composite can undergo several CO2 adsorption/desorption cycles without modification in its thermochemical stability and adsorption properties.