Pretreatment of Coal Fly Ash via Microwave Heating and Silicon Fusing for Synthesis of Zeolites

Coal fly ash (CFA) presents environmental challenges due to its abundance from coal combustion and difficult disposal issues, necessitating effective utilization strategies. This study explored the potential of combined microwave heating and silicon fusion as a pretreatment method for CFA, followed by zeolite molecular sieve synthesis. The aim is to enhance CFA activation, facilitate mullite transformation, and then extract valuable elements like silicon and aluminum. The synthesized zeolite molecular sieves exhibited a diamond-like structure with rich pore formations. XRD and XRF analysis identified that the predominant crystalline phases of the molecular sieves were Na₆Al₆Si₁₀O₃₂ (approximately 95.3%) with minor Na_3.6Al_3.6Si_12.4O₃₂, indicating NaP-type zeolites with a silicon-to-aluminum ratio of 1.78. In contrast, CFA's ratio was 1.24, suggesting that waste silicon powders served both as an activator and a supplementary silicon source. This innovative approach offered sustainable utilization of CFA, addressed environmental challenges, and promoted waste utilization. It exhibited tremendous potential in the environmental field with the advantages of low cost and environmental friendliness.