Silica-modified bismutite nanoparticles for enhanced adsorption and faster solar photocatalytic degradation of methylene blue

Herein, we report the synthesis of silica-modified self-assembled structures of bismutite (BSC) through a facile hydrothermal route. The incorporation of silica into the hybrid led to improved adsorption of cationic methylene blue (MB) dye due to electrostatic and hydrogen bond interactions with the silanol groups present on the catalyst surface. The enhanced adsorption of MB on the catalyst ensured better availability of oxidizing free radicals and charge carriers on the catalyst surface for photocatalytic degradation of MB, resulting in faster mineralization of organic species in the presence of solar light. The faster degradation could be observed as a blue shift in the absorbance of degradation intermediates during the reaction and was supported by further analysis using a mass spectrometer. Results from total organic carbon (TOC) analysis indicated 20 % better mineralization in presence of silica-modified BSC hybrids. This study reveals the importance of controlled incorporation of a suitable adsorbent to the semiconductor photocatalyst to overcome the sluggish reaction kinetics under sunlight, thus promoting faster degradation of organic species.