High-performance Li4SiO4 sorbents prepared from solid waste for CO2 capture

Abstract

Li4SiO4 shows great promise for cyclic high-temperature CO2 capture due to its excellent stability, high capacity, and low regeneration temperature. However, the practical application of Li4SiO4 is mainly limited by the high cost of raw materials, particularly lithium resources. Additionally, the heavy use of lithium-ion batteries (LIBs) in developing renewable energy sources raises concerns about the disposal of many waste LIBs. This article synthesized Li4SiO4 sorbent (BR-Li4SiO4) using spent lithium cobalt oxide (LiCoO2) cathodes and rice husk ash for CO2 capture. Meanwhile, we also prepared R-Li4SiO4/P-Li4SiO4 using commercial Li2CO3 and rice husk ash/commercial crystalline SiO2 as a comparison. The results show that the BR-Li4SiO4 sorbent exhibited excellent CO2 capture capacity and cycling stability at 675 °C, maintaining a stable capacity of 0.28 g/g under 100% CO2 after 30 cycles. BR-Li4SiO4 also demonstrated significantly reduced costs and a superior microstructure compared to R-Li4SiO4 and P-Li4SiO4. Furthermore, the impact of a simulated flue gas containing 15% CO2 and 10% H2O on Li4SiO4 adsorption was investigated. It was found that the adsorption of CO2 was decreased at low CO2 concentrations, but the addition of 10% H2O showed a slight enhancement in CO2 adsorption. Under a mixture of 15% CO2 + 10% H2O (balanced with N2), the maximum adsorption capacity of BR-Li4SiO4 was 0.17 g/g, and its optimal adsorption temperature decreased by 50 °C to 625 °C compared to 15% CO2. Therefore, this study will provide valuable insights into the industrial application of Li4SiO4 in CO2 adsorption.