Composites of mesoporous silica precipitated on nanofibrillated cellulose and microfibrillated cellulose: effect of fibre diameter and reaction conditions on particle size and mesopore diameter

Composites of MSNs (mesoporous silica nanoparticles) with nanofibrillated cellulose (NFC) and microfibrillated cellulose (MFC) were synthesized via in-situ precipitation. Controlling particle size distribution (PSD), pore diameter, and pore volume of mesoporous silica nanoparticles (MSNs) by cellulose nanofiber size has been investigated. In-situ precipitation on the 19 nm median diameter of NFC fibres produces MSNs in the diameter range 20–30 nm, the smallest MSN size reported. MSNs precipitated on MFC fibres with a 26 nm median diameter are 37% larger with broader size distribution, larger mesopore diameters, and lower specific surface area. The pore volume of MFC-MSNs composite was due to internal mesopores of MSNs and among particles and fibres, while it was primarily because of mesopores within MSNs in NFC-MSNs composite. Particle diameters were unaffected by varying the molar ratio of cellulose: TEOS (tetraethoxysilane) and reaction time. The reaction was mostly complete within only 10 min. The best NFC-MSN composite displayed a specific surface area of 567 m²/g with a saturated adsorption capacity of 134 mg/g of methylene blue (MB).