Nanosized MCM-41 silica from rice husk and its application for the removal of organic dyes from water

: A novel synthesis of a nanometric MCM-41 from biogenic silica obtained from rice husk is here presented. CTABr and Pluronic F127 surfactants were employed as templating agents to promote the formation of a long-range ordered 2D-hexagonal structure with cylindrical pores and to limit the particle growth at the nanoscale level thus resulting in a material with uniform particle size of 20-30 nm. The physico-chemical properties of this sample (RH-nanoMCM) were investigated through a multi-technique approach, including PXRD, 29Si MAS NMR, TEM, Z-potential and N2 physisorption analysis at 77 K. The results were compared to those of a nanometric MCM-41 synthesized from a silicon alkoxide precursor. The adsorption capacity of RH-nanoMCM towards the cationic dye rhodamine B from aqueous phase was investigated at different initial dye concentrations by means of UV-vis spectroscopy. Insight into the non-covalent interactions between the dye molecules and the adsorbent surface was gained by means of 1H and 13C MAS NMR spectroscopy and FT-IR spectroscopy.