One-step fabrication of size-controllable, biowaste-templated Li4SiO4 spherical pellets via freeze-drying method for cyclic CO2 capture

Abstract

High-temperature cyclic CO2 capture based on Li4SiO4 adsorbent has drawn extensive attentions in recent decades. Especially, the fabrication of Li4SiO4 adsorbent pellets with sufficient mechanical strength has been considered as an essential precondition for achieving its practical looping application. In this work, size-controllable Li4SiO4 spherical pellets were one-step fabricated via a novel freeze-drying method. And a typical industrial biowaste, bagasse, was employed as a low-cost and carbon–neutral pore-forming agent to enhance the CO2 capture performance of freeze-dried Li4SiO4 pellets. It is investigated that as the increasing of liquid-to-solid ratio, the diameter of pellets gradually decreases from 2.3 mm to 0.9 mm and the interior structure becomes dense and nonporous, resulting in the inhibition of CO2 capture capacity and the enhancement of mechanical strength. As a result, the LP2.5 exhibit a capacity of 0.15–0.17 g CO2/g adsorbent while that of LP7.5 decreases to only 0.07 g/g. To compensate this capacity decline, the biowaste bagasse was further acted as the pore-forming agent to improve the porosity and structure of LP 7.5 pellets, leading to an effective capacity promotion of 0.04–0.06 g/g. Meanwhile, however, it also leads to a slight decline of mechanical strength. All of above conclusions contribute to the future development and practical applications of Li4SiO4 adsorbent pellets.