High temperature capture of CO2 on lithium-based sorbents from rice husk ash

Highly efficient Li4SiO4 (lithium orthosilicate)-based sorbents for CO2 capture at high temperature, was developed using waste materials (rice husk ash). Two treated rice husk ash (RHA) samples (RHA1 and RHA2) were prepared and calcined at 800 °C in the presence of Li2CO3. Pure Li4SiO4 and RHA-based sorbents were characterized by X-ray fluorescence, X-ray diffraction, scanning electron microscopy, nitrogen adsorption, and thermogravimetry. CO2 sorption was tested through 15 carbonation/calcination cycles in a fixed bed reactor. The metals of RHA were doped with Li4SiO4 resulting to inhibited growth of the particles and increased pore volume and surface area. Thermal analyses indicated a much better CO2 absorption in Li4SiO4-based sorbent prepared from RHA1 (higher metal content sample) because the activation energies for the chemisorption process and diffusion process were smaller than that of pure Li4SiO4. RHA1-based sorbent also maintained higher capacities during the multiple cycles.