High-Purity Template-Free Mesoporous Silica Synthesized FROM Coal Fly Ash

Abstract

The study demonstrates a new method to create high-purity mesoporous silica from coal fly ash without using structure-directing agents. Divided into two stages, the process involves pre-treating the ash with Na2CO3, calcination, cooling, washing, and drying to yield a dehydrated sample. Subsequently, silica synthesis occurs through an acid refluxing technique using thermally activated coal fly ash with Na2CO3. Key factors impacting synthesis include acid content and liquid-to-solid ratio. The study extensively employs various characterization methods like XRF, XRD, FTIR, and BET analysis, revealing a 99.1 % purity in silica content, a surface area of 793.51 m2/g, and a pore size of 3.9 nm. Optimal conditions for this synthesis involve 80 °C temperature, 2-hour reaction time, 25 % hydrochloric acid concentration, and a 10 : 1 liquid-to-solid ratio. FTIR spectra demonstrate similarities between the obtained silica and commercial Sigma Aldrich silica. This innovative approach presents a promising avenue for generating top-quality silica from coal fly ash, potentially diversifying applications across industries reliant on high-performance silica materials.