CO^sub 2^ absorption properties of lithium sodium orthosilicate in the presence of water vapor at room temperature

We discovered that water vapor enhanced the CO2 absorption capacity of sodium orthosilicate (Li3NaSiO4) at as low as room temperature (RT) and the CO2 absorption property of Li3NaSiO4 in the presence of water vapor was larger than that of Li3NaSiO4 under a dry CO2 flow at high temperatures. Li3NaSiO4 powders were synthesized by heating a mixture of LiNO3, NaNO3, and amorphous SiO2 at 800 °C for 5 h in air. Thermogravimetry analysis shows that CO2 absorption of Li3NaSiO4, at RT, increased as a function of relative humidity and CO2 concentration. CO2 absorption of Li3NaSiO4 in the presence of water vapor resulted in the formation of NaHCO3 and Li2SiO3, as observed by X-ray diffraction (XRD), whereas >300 °C, Li3NaSiO4 reacted with CO2 to produce LiNaCO3 and Li2SiO3 under a dry CO2 flow. The CO2 absorption capacity of Li3NaSiO4, at RT, was enhanced in the presence of water vapor compared with Li3NaSiO4 under a dry CO2 flow at high temperatures. XRD determined that Li3NaSiO4 was regenerated by the heat treatment of the CO2-absorbed Li3NaSiO4 at 600 °C.