Fabrication of porous Li4SiO4 ceramic sorbent pebbles with high CO2 sorption capacity via the simple freeze-drying method

[Display omitted] •The Li4SiO4 sorbents with the porous structure were successfully fabricated via the simple Freeze-drying method.•The prepared FSC sorbents exhibited high CO2 sorption capacity of 0.305 g CO2/g sorbent and excellent cyclic durability.•The reaction channels formed by the columnar ice crystals can accelerate the reaction dynamics between the Li+ and CO2 gas. At present, the Li4SiO4 ceramic sorbents have displayed a great prospect for CO2 gas removal in the atmosphere owing to their high sorption capacity and stable sorption-desorption property. In this paper, a simple method combining the wet method and freeze-drying method is initially employed to fabricate Li4SiO4 sorbent with rich porosity and direction arrangement channels, which overcomes the dense interior structure, barren porosity, inferior adsorption stability, and costly production described in the previous literature. The effects of freeze way and temperature on the interior structure of Li4SiO4 sorbent were studied respectively. In the freeze-drying process, only the freeze-drying Li4SiO4 cylinder (FSC) green sorbents have columnar ice crystals in the interior owing to the temperature gradient, and the unidirectional alignment of pore channels can be obtained after the vacuum drying process due to the sublimation of ice crystals, which will improve CO2 capture capacity. Moreover, it can be seen from the optical image that the sorbent pebbles have a uniform distribution of diameter and sorbent samples of OSF (fabricated without the freezing process), FSP (fabricated with the freezing process), and FSC show excellent mechanical strength of 37.5 N, 22.5 N, and 0.43Mpa, respectively. Compared with OSP and FSP samples, the FSC sorbent performed superior CO2 sorption capacities (0.305 g CO2/g sorbent) and outstanding stability after 40 times cycles due to its optimal pore microstructure. Therefore, the prominent capture capacity and the satisfying crushing load of the FSC sorbents fabricated via the Freeze-drying method in this paper have promising prospects for CO2 removal.