Title: Extraction Of Pure Silicon Dioxide (White Soot) From Coal Fly Ash: A Comprehensive Review
Authors: Kholikulov D.B., Mutalibkhonov S.S., Khudoymuratov Sh.J., Khojiev Sh.T., Shaymanov I.I.
Volume: 9
Issue: 11
Pages: 167-182
Publication Date: 2025/11/28
Abstract:
- Coal fly ash, a major byproduct of coal combustion in thermal power plants and industrial sectors, represents a significant environmental and resource challenge. With over 780 million metric tons generated globally annually, primarily in Asia, coal fly ash contains substantial quantities of silicon dioxide (SiO?), alumina (Al?O?), and other valuable minerals. This review synthesizes approximately 60 peer-reviewed studies indexed in Scopus databases, examining recent advances in extracting high-purity silica from coal fly ash residues. Various extraction methodologies including alkaline leaching, acid leaching, sequential acid-alkaline processes, sol-gel synthesis, bioleaching, and thermal activation are critically evaluated. Research demonstrates that silica extraction efficiencies range from 40% to 52%, with purities varying between 80% to 99.3%, depending on the extraction technique employed. Advanced synthesis methods, particularly sol-gel approaches combined with proper pre-treatment, yield mesoporous silica nanoparticles with specific surface areas exceeding 650 mē/g and particle sizes under 100 nm. These materials find applications in catalysis, adsorption, environmental remediation, and advanced materials synthesis. The circular economy perspective of coal fly ash valorization presents both environmental benefits through waste reduction and economic advantages through production of high-value materials. This review highlights the technical feasibility, economic viability, and environmental sustainability of comprehensive coal fly ash utilization strategies.