Alkali silicates and structured mesoporous silicas from biomass power station wastes: the emergence of bio-MCMs

Abstract

The waste ashes from a commercial biomass combustion facility are successfully converted into mesoporous structured silica utilising a biorefinery approach, with potential high value applications in catalysis, adsorption and separation processes. Potassium silicate solutions are formed via a simple hydrothermal extraction of miscanthus bottom ashes, rich in amorphous silica, with a reproducible extraction of 60–70%. The extension and validation of a rapid and facile infrared method for the quantification of the silicate solutions is demonstrated with important industrial applications for continuous online screening and tuning of the silicate solution ratio and concentration. The alkali solutions from the waste ashes are used for the formation of a structured high surface area mesoporous silica, MCM-41 (1043 m² g⁻¹, 1.12 cm³ g⁻¹). The resulting mesoporous silica was analysed by XRD, N₂ adsorption porosimetry and TEM.