“…In the past few decades, great efforts have been made to synthesize FAU zeolite from CFA as the raw material. [25][26][27][28][29][30] For example, Aquino et al showed that the synthesis of FAU zeolite was performed under hydrothermal conditions after the activation of CFA with NaOH at high temperature; 31 Sen et al proposed an ultra-fast route for synthesizing nanoscale zeolite FAU assisted by microwave heating and ultrasonic waves under hydrothermal conditions from CFA. 32 Nevertheless, the current synthesis of FAU zeolite from CFA is always performed under hydrothermal conditions, and requires a large amount of water as a solvent, leading to low efficiency and environmental issues due to the formation of dissolved silica species in alkaline media and the production of a large amount of polluted water.…”