Preparation of cage-like nano-CaCO3 hollow spheres for enhanced CO2 sorption

Abstract

Cage-like nano-CaCO₃ hollow spheres with different cavity diameters for CO₂ sorption were prepared using the template-directed synthesis method. Carbon sphere templates with different diameters were synthesized via a hydrothermal reaction of starch under variable conditions. Field emission scanning electron microscopy (SEM) and transmission electron microscope (TEM) images indicated that the synthesized cage-like nano-CaCO₃ hollow spheres had different cavity diameters of 0.52 μm, 1.62 μm and 2.93 μm. The hollow sphere shells were composed of many uniform nanoparticles with diameters of approximately 80 nm, as supported by the X-ray diffraction (XRD) results. Furthermore, the CO₂ sorption properties of the cage-like nano-CaCO₃ hollow spheres were analyzed by thermo-gravimetric analysis (TGA). The sorption capacity of the optimum sample with a diameter of 1.62 μm reached the maximal theoretical value of 0.786 g_CO2 g_CaO⁻¹ at 600 °C and exceeded the sorption capacity of the reference nano-CaCO₃ sorbents by 45%. The sorption properties of the sample within the rapid reaction stage at the different temperatures of 550 °C, 600 °C and 650 °C were also evaluated. The results demonstrated that the sample exhibited a 30% higher sorption rate than nano-CaCO₃. Therefore, cage-like nano-CaCO₃ hollow spheres possess enhanced CO₂ sorption capacity and higher sorption rates.