High purity silica aerogel particles and nano-alumina particles obtained from fly ash: A novel method and potential applications

The continuous surge in global electricity demand has led to a substantial generation and accumulation of fly ash (FA), with existing resource utilization technologies demonstrating low efficiency and low value-added productions. This limitation impedes FA recycling and poses environmental pollution risks. In this study, an efficient and easily implemented cascaded process including alkali fusion, acid leaching, sol-gel and gel-washing was introduced. Results showed that this method can simultaneously synthesize high-purity silica aerogel particles (SAP, with SiO 2 content of 99.01 %) and nano-alumina particles (NAP, with Al 2 O 3 content of 98.34 %), and the silicon extraction efficiency can reach approximately 93 %. Furthermore, the systematic evaluation of SAP and NAP as dual-functional additives revealed their enhancing effect on the thermal insulation and flame-retardant properties of composite aerogels. This research proposes a novel pathway for high-value FA utilization. It also establishes a technical framework for cost-effective SAP and NAP preparation, potentially advancing sustainable development in related industries.