Development and evaluation of a solid-liquid composite CO2 adsorbent using rice husk from waste distiller's grains

As a solid waste in Baijiu production, rice husk of distiller's grains is considered as a low-cost biomass resource. To promote the resource utilization of distiller's grains, the hydrophobic modified rice husk biochar (DRHC) was prepared from solid waste of distiller's grains as precursor. DRHC was doped into hydrophobic silica as a solid phase material and an aqueous solution of 50 wt% K₂CO₃ was chosen as a liquid phase material. The solid-liquid composite adsorbents, prepared using a high-speed stirring method, exhibited a core-shell structure with a particle size of 52.98 μm. The adsorption capacity of the solid-liquid composite adsorbent increased as the addition of DRHC in the solid phase shell rose. The adsorption capacity of the composite adsorbent prepared with pure hydrophobic SiO₂ was 1.49 mmol/g, while the composite adsorbent had a capacity of up to 5.2 mmol/g when the addition of DRHC in the shell was 20 wt%. After 10 absorption-desorption cycles, the adsorption capacity of the composite adsorbent decreased by 13.8 %. The solid-liquid composite adsorbent could achieve the synergistic adsorption of the shell and the core. In this study, liquid absorbent and solid adsorbent were combined in a simple way, and the composite adsorbent effectively improved the adsorption capacity of CO₂, and also provided a new idea for the high-value utilization of distiller's grains.