Synthesis of Large Surface Area Mesoporous Silica Nanoparticles from (NH4)2SiF6-NH4F Solution Produced from Coal Fly Ash

A new process for the controlled-synthesis of large surface area mesoporous silica nanoparticles (MSNs) from the unique (NH 4 ) 2 SiF 6 -NH 4 F solution produced from coal fly ash was developed using template assisted rapid chemical precipitation method. This work achieved the synthesis of MSNs with specific surface area (SSA) (~ 500 m 2 /g—1064 m 2 /g), small particle size (~ 90 nm- 133 nm) with narrow pore size distribution ranging between (7.56 nm- 20.11 nm) and reduced agglomeration condition by proposing a unique reactant’s feeding pattern and studying other parameters aiding the controlled synthesis process. The effect of high concentration fluoride ion on cationic cetyltrimethylammonium bromide (CTAB) template was also investigated. A novel CTAB removal method from the highly porous cavities of the silica nanoparticles under mild conditions was proposed. At 50 °C and atmospheric pressure, the foam fractionation technique showed 61% efficiency of CTAB removal while maintaining the porous structure and surface silanol of the particles compared with the traditional calcination method, providing green, economic and sustainable method for surfactant removal in MSNs.