CO2 capture using lithium-based sorbents prepared with construction and demolition wastes as raw materials

CO2 capture was tested using lithium silicates prepared with construction and demolition waste materials (CDWM) to climate change mitigation. Four types of CDWM with high silicon and aluminum content were evaluated: sand, block, ceramic sanitary ware (CSW), and concrete wastes. CDWM were characterized by XRF, XRD and SEM-EDS; subsequently, the non-conventional precursors were mixed with LiOH and thermally treated in two stages: at 250 and 550 °C. Li4SiO4 was synthesized using conventional SiO2, applying the same synthesis method, and used as a reference. Li4SiO4, Li2SiO3 and LiAlO2 crystalline phases were obtained from all CDWM. Additionally, Li2CaSiO4 was detected in the case of wastes with high calcium content (block and concrete). The prepared Li4SiO4 samples were evaluated using the TGA technique for CO2 capture in dynamic and isothermal modes. The bulk CO2 adsorption in the Li4SiO4 prepared with CDWM started at a lower temperature (380 °C) than the material prepared with conventional precursors (500 °C). The temperature of CO2 sorption maxima was estimated at around 600 °C, being the Li4SiO4 prepared with block waste the material with the best performance. According to the isothermal analysis, the block-derived lithium silicate achieved a maximum CO2 capture capacity of 183 mg/g at 580 °C with PCO2 = 0.2; the desorption was observed above this temperature. The kinetic results (Avrami Eroffev model) were similar to those of Li4SiO4 prepared with conventional SiO2. Moreover, the stability of the materials was demonstrated during 20 cycles of the sorption-desorption process, displaying a constant sorption capacity of 180 CO2 mg/g.