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.